From 5b75db32fa20fd993aa11b1dc8de083c80e4ca30 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sat, 14 Dec 2024 20:04:28 +0800
Subject: [PATCH 01/13] .

---
 build.mill                                    |  2 +-
 docs/modules/ROOT/nav.adoc                    |  5 ++-
 .../ROOT/pages/comparisons/unique.adoc        |  4 +-
 docs/modules/ROOT/pages/index.adoc            |  4 +-
 .../large-builds.adoc => large/large.adoc}    | 27 +++---------
 .../ROOT/pages/large/multi-file-builds.adoc   | 16 +++++++
 .../ROOT/pages/large/selective-execution.adoc | 44 +++++++++++++++++++
 .../ROOT/pages/migrating/migrating.adoc       |  2 +-
 .../10-multi-file-builds/bar/package.mill     |  0
 .../bar/qux/mymodule/src/BarQux.scala         |  0
 .../10-multi-file-builds/bar/qux/package.mill |  0
 .../multi}/10-multi-file-builds/build.mill    |  0
 .../10-multi-file-builds/foo/package.mill     |  0
 .../10-multi-file-builds/foo/src/Foo.scala    |  0
 .../multi}/11-helper-files/build.mill         |  0
 .../multi}/11-helper-files/foo/package.mill   |  0
 .../multi}/11-helper-files/foo/src/Foo.scala  |  0
 .../multi}/11-helper-files/foo/versions.mill  |  0
 .../multi}/11-helper-files/src/Main.scala     |  0
 .../multi}/11-helper-files/util.mill          |  0
 .../multi}/12-helper-files-sc/build.sc        |  0
 .../multi}/12-helper-files-sc/foo/package.sc  |  0
 .../12-helper-files-sc/foo/src/Foo.scala      |  0
 .../multi}/12-helper-files-sc/foo/versions.sc |  0
 .../multi}/12-helper-files-sc/src/Main.scala  |  0
 .../multi}/12-helper-files-sc/util.sc         |  0
 .../build.mill.scala                          |  0
 .../foo/package.mill.scala                    |  0
 .../foo/src/Foo.scala                         |  0
 .../foo/versions.mill.scala                   |  0
 .../13-helper-files-mill-scala/src/Main.scala |  0
 .../util.mill.scala                           |  0
 .../bar/src/bar/Bar.java                      |  0
 .../bar/test/src/bar/BarTests.java            |  0
 .../9-selective-execution/build.mill          |  3 +-
 .../foo/src/foo/Foo.java                      |  0
 .../foo/test/src/bar/FooTests.java            |  0
 .../qux/src/qux/Qux.java                      |  0
 .../qux/test/src/qux/QuxTests.java            |  0
 example/package.mill                          |  7 ++-
 40 files changed, 83 insertions(+), 31 deletions(-)
 rename docs/modules/ROOT/pages/{depth/large-builds.adoc => large/large.adoc} (59%)
 create mode 100644 docs/modules/ROOT/pages/large/multi-file-builds.adoc
 create mode 100644 docs/modules/ROOT/pages/large/selective-execution.adoc
 rename example/{depth/large => large/multi}/10-multi-file-builds/bar/package.mill (100%)
 rename example/{depth/large => large/multi}/10-multi-file-builds/bar/qux/mymodule/src/BarQux.scala (100%)
 rename example/{depth/large => large/multi}/10-multi-file-builds/bar/qux/package.mill (100%)
 rename example/{depth/large => large/multi}/10-multi-file-builds/build.mill (100%)
 rename example/{depth/large => large/multi}/10-multi-file-builds/foo/package.mill (100%)
 rename example/{depth/large => large/multi}/10-multi-file-builds/foo/src/Foo.scala (100%)
 rename example/{depth/large => large/multi}/11-helper-files/build.mill (100%)
 rename example/{depth/large => large/multi}/11-helper-files/foo/package.mill (100%)
 rename example/{depth/large => large/multi}/11-helper-files/foo/src/Foo.scala (100%)
 rename example/{depth/large => large/multi}/11-helper-files/foo/versions.mill (100%)
 rename example/{depth/large => large/multi}/11-helper-files/src/Main.scala (100%)
 rename example/{depth/large => large/multi}/11-helper-files/util.mill (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/build.sc (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/foo/package.sc (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/foo/src/Foo.scala (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/foo/versions.sc (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/src/Main.scala (100%)
 rename example/{depth/large => large/multi}/12-helper-files-sc/util.sc (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/build.mill.scala (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/foo/package.mill.scala (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/foo/src/Foo.scala (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/foo/versions.mill.scala (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/src/Main.scala (100%)
 rename example/{depth/large => large/multi}/13-helper-files-mill-scala/util.mill.scala (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/bar/src/bar/Bar.java (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/bar/test/src/bar/BarTests.java (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/build.mill (99%)
 rename example/{depth/large => large/selective}/9-selective-execution/foo/src/foo/Foo.java (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/foo/test/src/bar/FooTests.java (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/qux/src/qux/Qux.java (100%)
 rename example/{depth/large => large/selective}/9-selective-execution/qux/test/src/qux/QuxTests.java (100%)

diff --git a/build.mill b/build.mill
index f114a1fe068..060db96f4fa 100644
--- a/build.mill
+++ b/build.mill
@@ -256,7 +256,7 @@ object Deps {
   }
 }
 
-def millVersion: T[String] = Task {
+def millVersion: T[String] = Task.Input {
   if (Task.env.contains("MILL_STABLE_VERSION")) VcsVersion.calcVcsState(Task.log).format()
   else "SNAPSHOT"
 }
diff --git a/docs/modules/ROOT/nav.adoc b/docs/modules/ROOT/nav.adoc
index 53bd6fa510c..8d848c59e04 100644
--- a/docs/modules/ROOT/nav.adoc
+++ b/docs/modules/ROOT/nav.adoc
@@ -95,8 +95,11 @@
 // These are things that most Mill developers would not encounter day to day,
 // but people developing Mill plugins or working on particularly large or
 // sophisticated Mill builds will need to understand.
+* xref:large/large.adoc[]
+** xref:large/selective-execution.adoc[]
+** xref:large/multi-file-builds.adoc[]
+
 * Mill In Depth
-** xref:depth/large-builds.adoc[]
 ** xref:depth/sandboxing.adoc[]
 ** xref:depth/evaluation-model.adoc[]
 ** xref:depth/design-principles.adoc[]
diff --git a/docs/modules/ROOT/pages/comparisons/unique.adoc b/docs/modules/ROOT/pages/comparisons/unique.adoc
index be471c12b8e..b174510ba67 100644
--- a/docs/modules/ROOT/pages/comparisons/unique.adoc
+++ b/docs/modules/ROOT/pages/comparisons/unique.adoc
@@ -85,8 +85,8 @@ xref:android/java.adoc[Android], and has demonstrated the ability to branch out
 more distant toolchains like xref:extending/example-typescript-support.adoc[Typescript]
 and xref:extending/example-python-support.adoc[Python].
 
-Mill also works well with xref:depth/large-builds.adoc[large builds]: its build logic can be
-split into multiple folders, is incrementally compiled,
+Mill also works well with xref:large/large.adoc[large builds]: its build logic can be
+xref:large/multi-file-builds.adoc[split into multiple folders], is incrementally compiled,
 lazily initialized, and automatically cached and parallelized. That means that even large
 codebases can remain fast and responsive: Mill's own build easily manages over 400 modules,
 and the tool can likely handle thousands of modules without issue.
diff --git a/docs/modules/ROOT/pages/index.adoc b/docs/modules/ROOT/pages/index.adoc
index 2bec2abd99e..c34ad0f7da1 100644
--- a/docs/modules/ROOT/pages/index.adoc
+++ b/docs/modules/ROOT/pages/index.adoc
@@ -13,7 +13,7 @@ or xref:comparisons/gradle.adoc[2-4x faster than Gradle]
 helps keep builds clean and understandable
 
 * Mill is an easier alternative to https://bazel.build/[Bazel]
-for xref:depth/large-builds.adoc[large multi-language monorepos] with hundreds of modules
+for xref:large/large.adoc[large multi-language monorepos] with hundreds of modules
 
 To get started using Mill, see the language-specific introductory documentation linked below:
 
@@ -37,7 +37,7 @@ Java platform's performance and usability:
 xref:depth/evaluation-model.adoc#_caching_at_each_layer_of_the_evaluation_model[caches]
 and xref:cli/flags.adoc#_jobs_j[parallelizes] build tasks to keep local development fast,
 and avoids the long configuration times seen in other tools like Gradle or SBT.
-xref:depth/large-builds.adoc#_selective_execution[Selective execution] keeps
+xref:large/selective-execution.adoc[Selective execution] keeps
 CI validation times short by only running the tests necessary to validate a code change.
 
 * *Maintainability*: Mill's config and xref:javalib/intro.adoc#_custom_build_logic[custom logic]
diff --git a/docs/modules/ROOT/pages/depth/large-builds.adoc b/docs/modules/ROOT/pages/large/large.adoc
similarity index 59%
rename from docs/modules/ROOT/pages/depth/large-builds.adoc
rename to docs/modules/ROOT/pages/large/large.adoc
index bdfa62d5334..9c0c428adab 100644
--- a/docs/modules/ROOT/pages/depth/large-builds.adoc
+++ b/docs/modules/ROOT/pages/large/large.adoc
@@ -1,7 +1,4 @@
 = Large Builds and Monorepos
-:page-aliases: Structuring_Large_Builds.adoc
-
-include::partial$gtag-config.adoc[]
 
 This section walks through Mill features and techniques used for managing large builds.
 While Mill works great for small single-module projects, it is also able to work
@@ -10,25 +7,13 @@ https://github.com/com-lihaoyi/mill[com-lihaoyi/mill] project has ~400 modules,
 other proprietary projects may have many more.
 
 Mill modules are cheap. Having more modules does not significantly impact performance
-or resource usage, build files are incrementally re-compiled when modified, and modules are 
-lazily loaded and initialized only when needed. So you are encouraged to break up your project 
+or resource usage, build files are incrementally re-compiled when modified, and modules are
+lazily loaded and initialized only when needed. So you are encouraged to break up your project
 into modules to manage the layering of your codebase or benefit from parallelism.
 
-== Selective Execution
-
-
-include::partial$example/depth/large/9-selective-execution.adoc[]
-
-== Multi-file Builds
-
-include::partial$example/depth/large/10-multi-file-builds.adoc[]
-
-== Helper Files
-
-include::partial$example/depth/large/11-helper-files.adoc[]
-
-== Legacy `.sc` extension
-
-include::partial$example/depth/large/12-helper-files-sc.adoc[]
+Apart from Mill's basic scalability and performance, Mill also comes with many features
+that can be utilized to help you manage the build system of a large project or codebase:
 
+* xref:large/selective-execution.adoc[]
 
+* xref:large/multi-file-builds.adoc[]
\ No newline at end of file
diff --git a/docs/modules/ROOT/pages/large/multi-file-builds.adoc b/docs/modules/ROOT/pages/large/multi-file-builds.adoc
new file mode 100644
index 00000000000..b2f363c51d3
--- /dev/null
+++ b/docs/modules/ROOT/pages/large/multi-file-builds.adoc
@@ -0,0 +1,16 @@
+= Multi-File Builds
+:page-aliases: Structuring_Large_Builds.adoc
+
+include::partial$gtag-config.adoc[]
+
+include::partial$example/large/multi/10-multi-file-builds.adoc[]
+
+== Helper Files
+
+include::partial$example/large/multi/11-helper-files.adoc[]
+
+== Legacy `.sc` extension
+
+include::partial$example/large/multi/12-helper-files-sc.adoc[]
+
+
diff --git a/docs/modules/ROOT/pages/large/selective-execution.adoc b/docs/modules/ROOT/pages/large/selective-execution.adoc
new file mode 100644
index 00000000000..75d7c41965b
--- /dev/null
+++ b/docs/modules/ROOT/pages/large/selective-execution.adoc
@@ -0,0 +1,44 @@
+= Selective Execution
+
+include::partial$gtag-config.adoc[]
+
+
+include::partial$example/large/selective/9-selective-execution.adoc[]
+
+
+== Reproducibility and Determinism
+
+Selective execution relies on the inputs to your project being deterministic
+and reproducible, except for the code changes between the two versions, so that
+Mill can compare the state of the build inputs before and after and only run
+tasks downstream of those that changed. This is usually the case, but there are
+some subtleties to be aware of:
+
+- *Dynamic `Task.Input` to capture Git metadata must be disabled*, e.g. using
+  https://github.com/lefou/mill-vcs-version[mill-vcs-version]. The easiest way to do
+  this is to guard such dynamic inputs on an environment variable, such that
+  in most scenarios it returns a constant `"SNAPSHOT"` string, and only when
+  necessary do you pass in the environment variable to compute a real version (e.g.
+  during publishing)
+
+```scala
+def myProjectVersion: T[String] = Task.Input {
+  if (Task.env.contains("MY_PROJECT_STABLE_VERSION")) VcsVersion.calcVcsState(Task.log).format()
+  else "SNAPSHOT"
+}
+```
+
+- *The filesystem layout and position of the before/after codebases must be exactly
+  the same*. This is not an issue when running `selective.prepare`/`selective.run` on
+  the same folder on one machine, but if the two calls are run on separate machines
+  you need to make sure the directory path is the same.
+
+- *You must use the same Operating System amd Filesystem*, as differences there will
+  cause the filesystem signatures to change and thus spuriously trigger downstream tasks.
+  e.g. you cannot run `selective.prepare` on a Windows machine and `selective.run` on Linux
+
+- *Filesystem permissions must be preserved before/after*. e.g. running `selective,run}`
+  on different Github Actions machines sharing artifacts can cause issues as
+  `upload-artifact`/`download-artifact` https://github.com/actions/download-artifact#permission-loss[does not preserve filesystem permissions].
+  If this is an issue, you can run `chmod -R . 777` before each of `selective.{prepare,run}`
+  to ensure they have the exact same filesystem permissions.
diff --git a/docs/modules/ROOT/pages/migrating/migrating.adoc b/docs/modules/ROOT/pages/migrating/migrating.adoc
index 639ce84a3aa..aca914c3ee3 100644
--- a/docs/modules/ROOT/pages/migrating/migrating.adoc
+++ b/docs/modules/ROOT/pages/migrating/migrating.adoc
@@ -283,7 +283,7 @@ to see which ones may help:
 
 * xref:fundamentals/modules.adoc#_trait_modules[Trait Modules] to centralize common config
 
-* xref:depth/large-builds.adoc#_multi_file_builds[Multi-File Builds] to let you co-locate
+* xref:large/multi-file-builds.adoc[Multi-File Builds] to let you co-locate
   build logic and the code being built
 
 * xref:extending/writing-plugins.adoc[Writing and Publishing your own Mill Plugins]
diff --git a/example/depth/large/10-multi-file-builds/bar/package.mill b/example/large/multi/10-multi-file-builds/bar/package.mill
similarity index 100%
rename from example/depth/large/10-multi-file-builds/bar/package.mill
rename to example/large/multi/10-multi-file-builds/bar/package.mill
diff --git a/example/depth/large/10-multi-file-builds/bar/qux/mymodule/src/BarQux.scala b/example/large/multi/10-multi-file-builds/bar/qux/mymodule/src/BarQux.scala
similarity index 100%
rename from example/depth/large/10-multi-file-builds/bar/qux/mymodule/src/BarQux.scala
rename to example/large/multi/10-multi-file-builds/bar/qux/mymodule/src/BarQux.scala
diff --git a/example/depth/large/10-multi-file-builds/bar/qux/package.mill b/example/large/multi/10-multi-file-builds/bar/qux/package.mill
similarity index 100%
rename from example/depth/large/10-multi-file-builds/bar/qux/package.mill
rename to example/large/multi/10-multi-file-builds/bar/qux/package.mill
diff --git a/example/depth/large/10-multi-file-builds/build.mill b/example/large/multi/10-multi-file-builds/build.mill
similarity index 100%
rename from example/depth/large/10-multi-file-builds/build.mill
rename to example/large/multi/10-multi-file-builds/build.mill
diff --git a/example/depth/large/10-multi-file-builds/foo/package.mill b/example/large/multi/10-multi-file-builds/foo/package.mill
similarity index 100%
rename from example/depth/large/10-multi-file-builds/foo/package.mill
rename to example/large/multi/10-multi-file-builds/foo/package.mill
diff --git a/example/depth/large/10-multi-file-builds/foo/src/Foo.scala b/example/large/multi/10-multi-file-builds/foo/src/Foo.scala
similarity index 100%
rename from example/depth/large/10-multi-file-builds/foo/src/Foo.scala
rename to example/large/multi/10-multi-file-builds/foo/src/Foo.scala
diff --git a/example/depth/large/11-helper-files/build.mill b/example/large/multi/11-helper-files/build.mill
similarity index 100%
rename from example/depth/large/11-helper-files/build.mill
rename to example/large/multi/11-helper-files/build.mill
diff --git a/example/depth/large/11-helper-files/foo/package.mill b/example/large/multi/11-helper-files/foo/package.mill
similarity index 100%
rename from example/depth/large/11-helper-files/foo/package.mill
rename to example/large/multi/11-helper-files/foo/package.mill
diff --git a/example/depth/large/11-helper-files/foo/src/Foo.scala b/example/large/multi/11-helper-files/foo/src/Foo.scala
similarity index 100%
rename from example/depth/large/11-helper-files/foo/src/Foo.scala
rename to example/large/multi/11-helper-files/foo/src/Foo.scala
diff --git a/example/depth/large/11-helper-files/foo/versions.mill b/example/large/multi/11-helper-files/foo/versions.mill
similarity index 100%
rename from example/depth/large/11-helper-files/foo/versions.mill
rename to example/large/multi/11-helper-files/foo/versions.mill
diff --git a/example/depth/large/11-helper-files/src/Main.scala b/example/large/multi/11-helper-files/src/Main.scala
similarity index 100%
rename from example/depth/large/11-helper-files/src/Main.scala
rename to example/large/multi/11-helper-files/src/Main.scala
diff --git a/example/depth/large/11-helper-files/util.mill b/example/large/multi/11-helper-files/util.mill
similarity index 100%
rename from example/depth/large/11-helper-files/util.mill
rename to example/large/multi/11-helper-files/util.mill
diff --git a/example/depth/large/12-helper-files-sc/build.sc b/example/large/multi/12-helper-files-sc/build.sc
similarity index 100%
rename from example/depth/large/12-helper-files-sc/build.sc
rename to example/large/multi/12-helper-files-sc/build.sc
diff --git a/example/depth/large/12-helper-files-sc/foo/package.sc b/example/large/multi/12-helper-files-sc/foo/package.sc
similarity index 100%
rename from example/depth/large/12-helper-files-sc/foo/package.sc
rename to example/large/multi/12-helper-files-sc/foo/package.sc
diff --git a/example/depth/large/12-helper-files-sc/foo/src/Foo.scala b/example/large/multi/12-helper-files-sc/foo/src/Foo.scala
similarity index 100%
rename from example/depth/large/12-helper-files-sc/foo/src/Foo.scala
rename to example/large/multi/12-helper-files-sc/foo/src/Foo.scala
diff --git a/example/depth/large/12-helper-files-sc/foo/versions.sc b/example/large/multi/12-helper-files-sc/foo/versions.sc
similarity index 100%
rename from example/depth/large/12-helper-files-sc/foo/versions.sc
rename to example/large/multi/12-helper-files-sc/foo/versions.sc
diff --git a/example/depth/large/12-helper-files-sc/src/Main.scala b/example/large/multi/12-helper-files-sc/src/Main.scala
similarity index 100%
rename from example/depth/large/12-helper-files-sc/src/Main.scala
rename to example/large/multi/12-helper-files-sc/src/Main.scala
diff --git a/example/depth/large/12-helper-files-sc/util.sc b/example/large/multi/12-helper-files-sc/util.sc
similarity index 100%
rename from example/depth/large/12-helper-files-sc/util.sc
rename to example/large/multi/12-helper-files-sc/util.sc
diff --git a/example/depth/large/13-helper-files-mill-scala/build.mill.scala b/example/large/multi/13-helper-files-mill-scala/build.mill.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/build.mill.scala
rename to example/large/multi/13-helper-files-mill-scala/build.mill.scala
diff --git a/example/depth/large/13-helper-files-mill-scala/foo/package.mill.scala b/example/large/multi/13-helper-files-mill-scala/foo/package.mill.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/foo/package.mill.scala
rename to example/large/multi/13-helper-files-mill-scala/foo/package.mill.scala
diff --git a/example/depth/large/13-helper-files-mill-scala/foo/src/Foo.scala b/example/large/multi/13-helper-files-mill-scala/foo/src/Foo.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/foo/src/Foo.scala
rename to example/large/multi/13-helper-files-mill-scala/foo/src/Foo.scala
diff --git a/example/depth/large/13-helper-files-mill-scala/foo/versions.mill.scala b/example/large/multi/13-helper-files-mill-scala/foo/versions.mill.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/foo/versions.mill.scala
rename to example/large/multi/13-helper-files-mill-scala/foo/versions.mill.scala
diff --git a/example/depth/large/13-helper-files-mill-scala/src/Main.scala b/example/large/multi/13-helper-files-mill-scala/src/Main.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/src/Main.scala
rename to example/large/multi/13-helper-files-mill-scala/src/Main.scala
diff --git a/example/depth/large/13-helper-files-mill-scala/util.mill.scala b/example/large/multi/13-helper-files-mill-scala/util.mill.scala
similarity index 100%
rename from example/depth/large/13-helper-files-mill-scala/util.mill.scala
rename to example/large/multi/13-helper-files-mill-scala/util.mill.scala
diff --git a/example/depth/large/9-selective-execution/bar/src/bar/Bar.java b/example/large/selective/9-selective-execution/bar/src/bar/Bar.java
similarity index 100%
rename from example/depth/large/9-selective-execution/bar/src/bar/Bar.java
rename to example/large/selective/9-selective-execution/bar/src/bar/Bar.java
diff --git a/example/depth/large/9-selective-execution/bar/test/src/bar/BarTests.java b/example/large/selective/9-selective-execution/bar/test/src/bar/BarTests.java
similarity index 100%
rename from example/depth/large/9-selective-execution/bar/test/src/bar/BarTests.java
rename to example/large/selective/9-selective-execution/bar/test/src/bar/BarTests.java
diff --git a/example/depth/large/9-selective-execution/build.mill b/example/large/selective/9-selective-execution/build.mill
similarity index 99%
rename from example/depth/large/9-selective-execution/build.mill
rename to example/large/selective/9-selective-execution/build.mill
index ea5f136b14d..095ee7675a3 100644
--- a/example/depth/large/9-selective-execution/build.mill
+++ b/example/large/selective/9-selective-execution/build.mill
@@ -22,7 +22,7 @@
 // ```bash
 // > git checkout main # start from the target branch of the PR
 //
-// > ./mill selective.prepare __.test
+// > ./mill selective.prepare
 //
 // > git checkout pull-request-branch # go to the pull request branch
 //
@@ -105,3 +105,4 @@ Test run bar.BarTests finished: 0 failed, 0 ignored, 1 total, ...
 // tasks non-selectively, which is convenient if you want to conditionally disable selective
 // execution (e.g. perhaps you want to perform selective execution on pre-merge on pull
 // requests but not post-merge on the main branch)
+//
diff --git a/example/depth/large/9-selective-execution/foo/src/foo/Foo.java b/example/large/selective/9-selective-execution/foo/src/foo/Foo.java
similarity index 100%
rename from example/depth/large/9-selective-execution/foo/src/foo/Foo.java
rename to example/large/selective/9-selective-execution/foo/src/foo/Foo.java
diff --git a/example/depth/large/9-selective-execution/foo/test/src/bar/FooTests.java b/example/large/selective/9-selective-execution/foo/test/src/bar/FooTests.java
similarity index 100%
rename from example/depth/large/9-selective-execution/foo/test/src/bar/FooTests.java
rename to example/large/selective/9-selective-execution/foo/test/src/bar/FooTests.java
diff --git a/example/depth/large/9-selective-execution/qux/src/qux/Qux.java b/example/large/selective/9-selective-execution/qux/src/qux/Qux.java
similarity index 100%
rename from example/depth/large/9-selective-execution/qux/src/qux/Qux.java
rename to example/large/selective/9-selective-execution/qux/src/qux/Qux.java
diff --git a/example/depth/large/9-selective-execution/qux/test/src/qux/QuxTests.java b/example/large/selective/9-selective-execution/qux/test/src/qux/QuxTests.java
similarity index 100%
rename from example/depth/large/9-selective-execution/qux/test/src/qux/QuxTests.java
rename to example/large/selective/9-selective-execution/qux/test/src/qux/QuxTests.java
diff --git a/example/package.mill b/example/package.mill
index bbbd900a963..79d9e84f908 100644
--- a/example/package.mill
+++ b/example/package.mill
@@ -89,11 +89,14 @@ object `package` extends RootModule with Module {
 
   object depth extends Module {
 
-    object large extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "large"))
-
     object sandbox extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "sandbox"))
     object javahome extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "javahome"))
   }
+  object large extends Module {
+
+    object selective extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "selective"))
+    object multi extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "multi"))
+  }
 
   object extending extends Module {
     object imports extends Cross[ExampleCrossModule](build.listIn(millSourcePath / "imports"))

From 3b29531208e7b56ae2fef74c1f41594e93520df5 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sat, 14 Dec 2024 23:50:02 +0800
Subject: [PATCH 02/13] basic invalidation and dependency forests

---
 .../client/src/mill/main/client/OutFiles.java |  3 ++
 main/codesig/src/ReachabilityAnalysis.scala   | 17 ++++-----
 main/codesig/src/ResolvedCalls.scala          | 17 +--------
 main/eval/src/mill/eval/EvaluatorCore.scala   | 30 +++++++++++++++-
 main/src/mill/main/SelectiveExecution.scala   | 18 +---------
 .../src/mill/util}/SpanningForest.scala       | 35 ++++++++++++++++---
 6 files changed, 70 insertions(+), 50 deletions(-)
 rename main/{codesig/src => util/src/mill/util}/SpanningForest.scala (72%)

diff --git a/main/client/src/mill/main/client/OutFiles.java b/main/client/src/mill/main/client/OutFiles.java
index 51be8714b36..ddc226c12e4 100644
--- a/main/client/src/mill/main/client/OutFiles.java
+++ b/main/client/src/mill/main/client/OutFiles.java
@@ -73,4 +73,7 @@ public class OutFiles {
    * root tasks changed so Mill can decide which tasks to execute.
    */
   public static final String millSelectiveExecution = "mill-selective-execution.json";
+
+  public static final String millDependencyForest = "mill-dependency-forest.json";
+  public static final String millInvalidationForest = "mill-invalidation-forest.json";
 }
diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index 116848bab9d..1a1dc22b354 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -1,7 +1,7 @@
 package mill.codesig
-import mill.util.Tarjans
+import mill.util.{SpanningForest, Tarjans}
 import upickle.default.{Writer, writer}
-import JvmModel._
+import JvmModel.*
 
 import scala.collection.immutable.SortedMap
 import ujson.Obj
@@ -126,15 +126,10 @@ object CallGraphAnalysis {
       }
       .toSet
 
-    def spanningTreeToJsonTree(node: SpanningForest.Node): ujson.Obj = {
-      ujson.Obj.from(
-        node.values.map { case (k, v) =>
-          indexToNodes(k).toString -> spanningTreeToJsonTree(v)
-        }
-      )
-    }
-
-    spanningTreeToJsonTree(SpanningForest.apply(indexGraphEdges, nodesWithChangedHashes))
+    SpanningForest.spanningTreeToJsonTree(
+      SpanningForest.apply(indexGraphEdges, nodesWithChangedHashes),
+      k => indexToNodes(k).toString
+    )
   }
 
   def indexGraphEdges(
diff --git a/main/codesig/src/ResolvedCalls.scala b/main/codesig/src/ResolvedCalls.scala
index 6bb5b5698f7..5a32697a17b 100644
--- a/main/codesig/src/ResolvedCalls.scala
+++ b/main/codesig/src/ResolvedCalls.scala
@@ -1,6 +1,7 @@
 package mill.codesig
 import JvmModel._
 import JType.{Cls => JCls}
+import mill.util.SpanningForest.breadthFirst
 import upickle.default.{ReadWriter, macroRW}
 
 case class ResolvedCalls(
@@ -188,20 +189,4 @@ object ResolvedCalls {
     )
   }
 
-  def breadthFirst[T](start: IterableOnce[T])(edges: T => IterableOnce[T]): Seq[T] = {
-    val seen = collection.mutable.Set.empty[T]
-    val seenList = collection.mutable.Buffer.empty[T]
-    val queued = collection.mutable.Queue.from(start)
-
-    while (queued.nonEmpty) {
-      val current = queued.dequeue()
-      seen.add(current)
-      seenList.append(current)
-
-      for (next <- edges(current).iterator) {
-        if (!seen.contains(next)) queued.enqueue(next)
-      }
-    }
-    seenList.toSeq
-  }
 }
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index 4bdc2f48fbd..b4ad304618f 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -5,12 +5,13 @@ import mill.api.Strict.Agg
 import mill.api._
 import mill.define._
 import mill.eval.Evaluator.TaskResult
-
+import mill.main.client.OutFiles
 import mill.util._
 
 import java.util.concurrent.atomic.{AtomicBoolean, AtomicInteger}
 import scala.collection.mutable
 import scala.concurrent._
+import scala.jdk.CollectionConverters.EnumerationHasAsScala
 
 /**
  * Core logic of evaluating tasks, without any user-facing helper methods
@@ -85,6 +86,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     val (classToTransitiveClasses, allTransitiveClassMethods) =
       CodeSigUtils.precomputeMethodNamesPerClass(sortedGroups)
 
+    val uncached = new java.util.concurrent.ConcurrentHashMap[Terminal, Unit]()
     def evaluateTerminals(
         terminals: Seq[Terminal],
         forkExecutionContext: mill.api.Ctx.Fork.Impl,
@@ -191,6 +193,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
                 threadId = threadNumberer.getThreadId(Thread.currentThread()),
                 cached = res.cached
               )
+              if (!res.cached) uncached.put(terminal, ())
 
               profileLogger.log(
                 ProfileLogger.Timing(
@@ -254,6 +257,31 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
 
     val results: Map[Task[_], TaskResult[(Val, Int)]] = results0.toMap
 
+    val reverseInterGroupDeps = interGroupDeps
+      .iterator
+      .flatMap{case (k, vs) => vs.map(_ -> k)}
+      .toSeq
+      .groupMap(_._1)(_._2)
+
+    val indexToTerminal = sortedGroups.keys().toArray
+    val terminalToIndex = indexToTerminal.zipWithIndex.toMap
+    val downstreamIndexEdges = indexToTerminal.map(t => reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+    val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+    os.write.over(
+      outPath / OutFiles.millInvalidationForest,
+      SpanningForest.spanningTreeToJsonTree(
+        SpanningForest(upstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet),
+        i => indexToTerminal(i).render
+      ).render(indent = 2)
+    )
+    os.write.over(
+      outPath / OutFiles.millDependencyForest,
+      SpanningForest.spanningTreeToJsonTree(
+        SpanningForest.apply(downstreamIndexEdges, indexToTerminal.indices.toSet),
+        i => indexToTerminal(i).render
+      ).render(indent = 2)
+    )
+
     EvaluatorCore.Results(
       goals.indexed.map(results(_).map(_._1).result),
       // result of flatMap may contain non-distinct entries,
diff --git a/main/src/mill/main/SelectiveExecution.scala b/main/src/mill/main/SelectiveExecution.scala
index 5b0f1a71c27..f310fa15785 100644
--- a/main/src/mill/main/SelectiveExecution.scala
+++ b/main/src/mill/main/SelectiveExecution.scala
@@ -4,6 +4,7 @@ import mill.api.Strict
 import mill.define.{InputImpl, NamedTask, Task}
 import mill.eval.{CodeSigUtils, Evaluator, Plan, Terminal}
 import mill.main.client.OutFiles
+import mill.util.SpanningForest.breadthFirst
 import mill.resolve.{Resolve, SelectMode}
 
 private[mill] object SelectiveExecution {
@@ -114,23 +115,6 @@ private[mill] object SelectiveExecution {
     breadthFirst(changedRootTasks)(downstreamEdgeMap.getOrElse(_, Nil))
   }
 
-  def breadthFirst[T](start: IterableOnce[T])(edges: T => IterableOnce[T]): Seq[T] = {
-    val seen = collection.mutable.Set.empty[T]
-    val seenList = collection.mutable.Buffer.empty[T]
-    val queued = collection.mutable.Queue.from(start)
-
-    while (queued.nonEmpty) {
-      val current = queued.dequeue()
-      seen.add(current)
-      seenList.append(current)
-
-      for (next <- edges(current).iterator) {
-        if (!seen.contains(next)) queued.enqueue(next)
-      }
-    }
-    seenList.toSeq
-  }
-
   def saveMetadata(evaluator: Evaluator, metadata: SelectiveExecution.Metadata): Unit = {
     os.write.over(
       evaluator.outPath / OutFiles.millSelectiveExecution,
diff --git a/main/codesig/src/SpanningForest.scala b/main/util/src/mill/util/SpanningForest.scala
similarity index 72%
rename from main/codesig/src/SpanningForest.scala
rename to main/util/src/mill/util/SpanningForest.scala
index a642cae82db..c2e3aeffb4a 100644
--- a/main/codesig/src/SpanningForest.scala
+++ b/main/util/src/mill/util/SpanningForest.scala
@@ -1,5 +1,6 @@
-package mill.codesig
-import collection.mutable
+package mill.util
+
+import scala.collection.mutable
 
 /**
  * Algorithm to compute the minimal spanning forest of a directed acyclic graph
@@ -11,8 +12,14 @@ import collection.mutable
  * Returns the forest as a [[Node]] structure with the top-level node containing
  * the roots of the forest
  */
-object SpanningForest {
-
+private[mill] object SpanningForest {
+  def spanningTreeToJsonTree(node: SpanningForest.Node, stringify: Int => String): ujson.Obj = {
+    ujson.Obj.from(
+      node.values.map { case (k, v) =>
+        stringify(k) -> spanningTreeToJsonTree(v, stringify)
+      }
+    )
+  }
   case class Node(values: mutable.Map[Int, Node] = mutable.Map())
   def apply(indexGraphEdges: Array[Array[Int]], importantVertices: Set[Int]): Node = {
     // Find all importantVertices which are "roots" with no incoming edges
@@ -35,7 +42,7 @@ object SpanningForest {
       .flatMap { case (vs, k) => vs.map((_, k)) }
       .groupMap(_._1)(_._2)
 
-    ResolvedCalls.breadthFirst(rootChangedNodeIndices) { index =>
+    breadthFirst(rootChangedNodeIndices) { index =>
       val nextIndices =
         downstreamGraphEdges.getOrElse(
           index,
@@ -54,4 +61,22 @@ object SpanningForest {
     }
     spanningForest
   }
+
+  def breadthFirst[T](start: IterableOnce[T])(edges: T => IterableOnce[T]): Seq[T] = {
+    val seen = collection.mutable.Set.empty[T]
+    val seenList = collection.mutable.Buffer.empty[T]
+    val queued = collection.mutable.Queue.from(start)
+
+    while (queued.nonEmpty) {
+      val current = queued.dequeue()
+      seen.add(current)
+      seenList.append(current)
+
+      for (next <- edges(current).iterator) {
+        if (!seen.contains(next)) queued.enqueue(next)
+      }
+    }
+    seenList.toSeq
+  }
+
 }

From 453754c5e7c68b3a100dec7f1cec66d127c5fd09 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 00:29:40 +0800
Subject: [PATCH 03/13] spanning forest fixes

---
 main/eval/src/mill/eval/EvaluatorCore.scala   |  4 +-
 main/util/src/mill/util/SpanningForest.scala  | 14 +++---
 .../src/mill/util/SpanningForestTests.scala   | 46 +++++++++++++++++++
 3 files changed, 55 insertions(+), 9 deletions(-)
 create mode 100644 main/util/test/src/mill/util/SpanningForestTests.scala

diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index b4ad304618f..b09261ea50f 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -87,6 +87,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
       CodeSigUtils.precomputeMethodNamesPerClass(sortedGroups)
 
     val uncached = new java.util.concurrent.ConcurrentHashMap[Terminal, Unit]()
+
     def evaluateTerminals(
         terminals: Seq[Terminal],
         forkExecutionContext: mill.api.Ctx.Fork.Impl,
@@ -267,6 +268,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     val terminalToIndex = indexToTerminal.zipWithIndex.toMap
     val downstreamIndexEdges = indexToTerminal.map(t => reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
     val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+
     os.write.over(
       outPath / OutFiles.millInvalidationForest,
       SpanningForest.spanningTreeToJsonTree(
@@ -277,7 +279,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     os.write.over(
       outPath / OutFiles.millDependencyForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest.apply(downstreamIndexEdges, indexToTerminal.indices.toSet),
+        SpanningForest(downstreamIndexEdges, indexToTerminal.indices.toSet),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
diff --git a/main/util/src/mill/util/SpanningForest.scala b/main/util/src/mill/util/SpanningForest.scala
index c2e3aeffb4a..b594d2f830e 100644
--- a/main/util/src/mill/util/SpanningForest.scala
+++ b/main/util/src/mill/util/SpanningForest.scala
@@ -15,9 +15,7 @@ import scala.collection.mutable
 private[mill] object SpanningForest {
   def spanningTreeToJsonTree(node: SpanningForest.Node, stringify: Int => String): ujson.Obj = {
     ujson.Obj.from(
-      node.values.map { case (k, v) =>
-        stringify(k) -> spanningTreeToJsonTree(v, stringify)
-      }
+      node.values.map { case (k, v) => stringify(k) -> spanningTreeToJsonTree(v, stringify) }
     )
   }
   case class Node(values: mutable.Map[Int, Node] = mutable.Map())
@@ -43,11 +41,11 @@ private[mill] object SpanningForest {
       .groupMap(_._1)(_._2)
 
     breadthFirst(rootChangedNodeIndices) { index =>
-      val nextIndices =
-        downstreamGraphEdges.getOrElse(
-          index,
-          Array[Int]()
-        ) // needed to add explicit type for Scala 3.5.0-RC6
+      // needed to add explicit type for Scala 3.5.0-RC6
+      val nextIndices = downstreamGraphEdges
+        .getOrElse(index, Array[Int]())
+        .filter(importantVertices)
+
       // We build up the spanningForest during a normal breadth first search,
       // using the `nodeMapping` to quickly find a vertice's tree node so we
       // can add children to it. We need to duplicate the `seen.contains` logic
diff --git a/main/util/test/src/mill/util/SpanningForestTests.scala b/main/util/test/src/mill/util/SpanningForestTests.scala
new file mode 100644
index 00000000000..a5e1de396c6
--- /dev/null
+++ b/main/util/test/src/mill/util/SpanningForestTests.scala
@@ -0,0 +1,46 @@
+package mill.util
+
+import utest.{TestSuite, Tests, test}
+import collection.mutable
+import SpanningForest.Node
+object SpanningForestTests extends TestSuite {
+
+  val tests = Tests {
+
+    test("test") {
+      val forest = SpanningForest.apply(
+        Array(
+          Array(1),
+          Array(2),
+          Array(3),
+          Array(),
+          Array(),
+        ),
+        Set(0)
+      )
+
+      val expected =           Node(
+        mutable.Map(
+          0 -> Node(
+            mutable.Map(
+              1 -> Node(
+                mutable.Map(
+                  2 -> Node(
+                    mutable.Map(
+                      3 -> Node(mutable.Map())
+                    )
+                  )
+                )
+              )
+            )
+          )
+        )
+      )
+
+      assert(forest == expected
+      )
+    }
+
+  }
+
+}

From 9650199fcfa30f91fcfce1219b3c3d62bfcaef48 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 00:42:03 +0800
Subject: [PATCH 04/13] wip

---
 main/codesig/src/ReachabilityAnalysis.scala  | 10 +++++++++-
 main/eval/src/mill/eval/EvaluatorCore.scala  |  4 ++--
 main/util/src/mill/util/SpanningForest.scala | 13 +++----------
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index 1a1dc22b354..9cf7d591b37 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -126,8 +126,16 @@ object CallGraphAnalysis {
       }
       .toSet
 
+    val reverseGraphMap = indexGraphEdges
+      .zipWithIndex
+      .flatMap { case (vs, k) => vs.map((_, k)) }
+      .groupMap(_._1)(_._2)
+
     SpanningForest.spanningTreeToJsonTree(
-      SpanningForest.apply(indexGraphEdges, nodesWithChangedHashes),
+      SpanningForest.apply(
+        indexGraphEdges.indices.map(reverseGraphMap(_)).toArray,
+        nodesWithChangedHashes
+      ),
       k => indexToNodes(k).toString
     )
   }
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index b09261ea50f..e5c6ca81bfb 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -272,14 +272,14 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     os.write.over(
       outPath / OutFiles.millInvalidationForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(upstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet),
+        SpanningForest(downstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
     os.write.over(
       outPath / OutFiles.millDependencyForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(downstreamIndexEdges, indexToTerminal.indices.toSet),
+        SpanningForest(upstreamIndexEdges, indexToTerminal.indices.toSet),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
diff --git a/main/util/src/mill/util/SpanningForest.scala b/main/util/src/mill/util/SpanningForest.scala
index b594d2f830e..bfd46878313 100644
--- a/main/util/src/mill/util/SpanningForest.scala
+++ b/main/util/src/mill/util/SpanningForest.scala
@@ -22,9 +22,8 @@ private[mill] object SpanningForest {
   def apply(indexGraphEdges: Array[Array[Int]], importantVertices: Set[Int]): Node = {
     // Find all importantVertices which are "roots" with no incoming edges
     // from other importantVertices
-    val rootChangedNodeIndices = importantVertices.filter(i =>
-      !indexGraphEdges(i).exists(importantVertices.contains(_))
-    )
+    val destinations = importantVertices.flatMap(indexGraphEdges(_))
+    val rootChangedNodeIndices = importantVertices.filter(!destinations.contains(_))
 
     // Prepare a mutable tree structure that we will return, pre-populated with
     // just the first level of nodes from the `rootChangedNodeIndices`, as well
@@ -35,15 +34,9 @@ private[mill] object SpanningForest {
 
     // Do a breadth first search from the `rootChangedNodeIndices` across the
     // reverse edges of the graph to build up the spanning forest
-    val downstreamGraphEdges = indexGraphEdges
-      .zipWithIndex
-      .flatMap { case (vs, k) => vs.map((_, k)) }
-      .groupMap(_._1)(_._2)
-
     breadthFirst(rootChangedNodeIndices) { index =>
       // needed to add explicit type for Scala 3.5.0-RC6
-      val nextIndices = downstreamGraphEdges
-        .getOrElse(index, Array[Int]())
+      val nextIndices = indexGraphEdges(index)
         .filter(importantVertices)
 
       // We build up the spanningForest during a normal breadth first search,

From 770379e49dc163500244a9b8c28265719419cf96 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 01:21:59 +0800
Subject: [PATCH 05/13] wip

---
 main/eval/src/mill/eval/EvaluatorCore.scala  | 11 ++++++--
 main/eval/src/mill/eval/GroupEvaluator.scala | 28 ++++++++++++++------
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index e5c6ca81bfb..7711c318285 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -87,6 +87,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
       CodeSigUtils.precomputeMethodNamesPerClass(sortedGroups)
 
     val uncached = new java.util.concurrent.ConcurrentHashMap[Terminal, Unit]()
+    val changedValueHash = new java.util.concurrent.ConcurrentHashMap[Terminal, Unit]()
 
     def evaluateTerminals(
         terminals: Seq[Terminal],
@@ -118,7 +119,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
           val taskResults =
             group.map(t => (t, TaskResult[(Val, Int)](failure, () => failure))).toMap
           futures(terminal) = Future.successful(
-            Some(GroupEvaluator.Results(taskResults, group.toSeq, false, -1, -1))
+            Some(GroupEvaluator.Results(taskResults, group.toSeq, false, -1, -1, false))
           )
         } else {
           futures(terminal) = Future.sequence(deps.map(futures)).map { upstreamValues =>
@@ -195,6 +196,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
                 cached = res.cached
               )
               if (!res.cached) uncached.put(terminal, ())
+              if (res.changedValueHash) changedValueHash.put(terminal, ())
 
               profileLogger.log(
                 ProfileLogger.Timing(
@@ -266,7 +268,12 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
 
     val indexToTerminal = sortedGroups.keys().toArray
     val terminalToIndex = indexToTerminal.zipWithIndex.toMap
-    val downstreamIndexEdges = indexToTerminal.map(t => reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+    val changedTerminalIndices = changedValueHash.keys().asScala.toSet
+    val downstreamIndexEdges = indexToTerminal
+      .map(t =>
+        if (changedTerminalIndices(t)) reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray
+        else Array.empty[Int]
+      )
     val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
 
     os.write.over(
diff --git a/main/eval/src/mill/eval/GroupEvaluator.scala b/main/eval/src/mill/eval/GroupEvaluator.scala
index 7ef94d96e7b..2486d90f22b 100644
--- a/main/eval/src/mill/eval/GroupEvaluator.scala
+++ b/main/eval/src/mill/eval/GroupEvaluator.scala
@@ -103,7 +103,7 @@ private[mill] trait GroupEvaluator {
             executionContext,
             exclusive
           )
-          GroupEvaluator.Results(newResults, newEvaluated.toSeq, null, inputsHash, -1)
+          GroupEvaluator.Results(newResults, newEvaluated.toSeq, null, inputsHash, -1, changedValueHash = false)
 
         case labelled: Terminal.Labelled[_] =>
           val out =
@@ -126,7 +126,7 @@ private[mill] trait GroupEvaluator {
               cached.isEmpty
           )
 
-          upToDateWorker.map((_, inputsHash)) orElse cached.flatMap(_._2) match {
+          upToDateWorker.map((_, inputsHash)) orElse cached.flatMap { case (inputHash, valOpt, valueHash) => valOpt.map((_, valueHash))} match {
             case Some((v, hashCode)) =>
               val res = Result.Success((v, hashCode))
               val newResults: Map[Task[_], TaskResult[(Val, Int)]] =
@@ -137,7 +137,8 @@ private[mill] trait GroupEvaluator {
                 Nil,
                 cached = true,
                 inputsHash,
-                -1
+                -1,
+                changedValueHash = false
               )
 
             case _ =>
@@ -160,12 +161,14 @@ private[mill] trait GroupEvaluator {
                   exclusive
                 )
 
-              newResults(labelled.task) match {
+              val valueHash = newResults(labelled.task) match {
                 case TaskResult(Result.Failure(_, Some((v, _))), _) =>
                   handleTaskResult(v, v.##, paths.meta, inputsHash, labelled)
+                  v.##
 
                 case TaskResult(Result.Success((v, _)), _) =>
                   handleTaskResult(v, v.##, paths.meta, inputsHash, labelled)
+                  v.##
 
                 case _ =>
                   // Wipe out any cached meta.json file that exists, so
@@ -173,14 +176,21 @@ private[mill] trait GroupEvaluator {
                   // assume it's associated with the possibly-borked state of the
                   // destPath after an evaluation failure.
                   os.remove.all(paths.meta)
+                  0
               }
 
+              mill.main.client.DebugLog.println("")
+              mill.main.client.DebugLog.println(labelled.render)
+              mill.main.client.DebugLog.println(cached.map(_._3).toString)
+              mill.main.client.DebugLog.println(valueHash.toString)
+
               GroupEvaluator.Results(
                 newResults,
                 newEvaluated.toSeq,
                 cached = if (labelled.task.isInstanceOf[InputImpl[_]]) null else false,
                 inputsHash,
-                cached.map(_._1).getOrElse(-1)
+                cached.map(_._1).getOrElse(-1),
+                !cached.map(_._3).contains(valueHash)
               )
           }
       }
@@ -383,7 +393,7 @@ private[mill] trait GroupEvaluator {
       inputsHash: Int,
       labelled: Terminal.Labelled[_],
       paths: EvaluatorPaths
-  ): Option[(Int, Option[(Val, Int)])] = {
+  ): Option[(Int, Option[Val], Int)] = {
     for {
       cached <-
         try Some(upickle.default.read[Evaluator.Cached](paths.meta.toIO))
@@ -405,7 +415,8 @@ private[mill] trait GroupEvaluator {
               None
             case NonFatal(_) => None
           }
-      } yield (Val(parsed), cached.valueHash)
+      } yield Val(parsed),
+      cached.valueHash
     )
   }
 
@@ -457,6 +468,7 @@ private[mill] object GroupEvaluator {
       newEvaluated: Seq[Task[_]],
       cached: java.lang.Boolean,
       inputsHash: Int,
-      previousInputsHash: Int
+      previousInputsHash: Int,
+      changedValueHash: Boolean
   )
 }

From 2b3c53c0269a594716b74ac2cfb5d2c3f9ab75e2 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 09:29:27 +0800
Subject: [PATCH 06/13] wip

---
 kotlinlib/package.mill                       |  1 +
 main/eval/src/mill/eval/EvaluatorCore.scala  | 22 +++++++++++---------
 main/eval/src/mill/eval/GroupEvaluator.scala |  5 -----
 3 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/kotlinlib/package.mill b/kotlinlib/package.mill
index f0fce59c5e8..bd551f16dca 100644
--- a/kotlinlib/package.mill
+++ b/kotlinlib/package.mill
@@ -25,6 +25,7 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
     BuildInfo.Value("freemarkerDep", Dep.unparse(build.Deps.RuntimeDeps.freemarker).get, "freemarker dependency (used for Dokka)")
   )
 
+
   trait MillKotlinModule extends build.MillPublishScalaModule {
     override def javacOptions = {
       val release =
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index 7711c318285..4be359f4e03 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -77,6 +77,16 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     val terminals0 = sortedGroups.keys().toVector
     val failed = new AtomicBoolean(false)
     val count = new AtomicInteger(1)
+    val indexToTerminal = sortedGroups.keys().toArray
+    val terminalToIndex = indexToTerminal.zipWithIndex.toMap
+    val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+    os.write.over(
+      outPath / OutFiles.millDependencyForest,
+      SpanningForest.spanningTreeToJsonTree(
+        SpanningForest(upstreamIndexEdges, indexToTerminal.indices.toSet),
+        i => indexToTerminal(i).render
+      ).render(indent = 2)
+    )
 
     val futures = mutable.Map.empty[Terminal, Future[Option[GroupEvaluator.Results]]]
 
@@ -266,15 +276,14 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
       .toSeq
       .groupMap(_._1)(_._2)
 
-    val indexToTerminal = sortedGroups.keys().toArray
-    val terminalToIndex = indexToTerminal.zipWithIndex.toMap
+
     val changedTerminalIndices = changedValueHash.keys().asScala.toSet
     val downstreamIndexEdges = indexToTerminal
       .map(t =>
         if (changedTerminalIndices(t)) reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray
         else Array.empty[Int]
       )
-    val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+
 
     os.write.over(
       outPath / OutFiles.millInvalidationForest,
@@ -283,13 +292,6 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
-    os.write.over(
-      outPath / OutFiles.millDependencyForest,
-      SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(upstreamIndexEdges, indexToTerminal.indices.toSet),
-        i => indexToTerminal(i).render
-      ).render(indent = 2)
-    )
 
     EvaluatorCore.Results(
       goals.indexed.map(results(_).map(_._1).result),
diff --git a/main/eval/src/mill/eval/GroupEvaluator.scala b/main/eval/src/mill/eval/GroupEvaluator.scala
index 2486d90f22b..11bff00d26e 100644
--- a/main/eval/src/mill/eval/GroupEvaluator.scala
+++ b/main/eval/src/mill/eval/GroupEvaluator.scala
@@ -179,11 +179,6 @@ private[mill] trait GroupEvaluator {
                   0
               }
 
-              mill.main.client.DebugLog.println("")
-              mill.main.client.DebugLog.println(labelled.render)
-              mill.main.client.DebugLog.println(cached.map(_._3).toString)
-              mill.main.client.DebugLog.println(valueHash.toString)
-
               GroupEvaluator.Results(
                 newResults,
                 newEvaluated.toSeq,

From 65673826d292d6ac340a1e01f5f91e5ec3f44f5e Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 10:07:14 +0800
Subject: [PATCH 07/13] mandatory methodCodeHashSignatures
 spanningInvalidationForest

---
 kotlinlib/package.mill                        | 10 +++++++-
 .../kotlinlib/worker/api/KotlinWorker.scala   |  2 +-
 main/codesig/src/Logger.scala                 | 25 +++++++++++--------
 main/codesig/src/ReachabilityAnalysis.scala   | 12 ++++-----
 main/codesig/test/src/Util.scala              |  2 +-
 .../src/mill/runner/MillBuildRootModule.scala |  5 +++-
 6 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/kotlinlib/package.mill b/kotlinlib/package.mill
index bd551f16dca..d714b916ce3 100644
--- a/kotlinlib/package.mill
+++ b/kotlinlib/package.mill
@@ -12,10 +12,19 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
   def moduleDeps = Seq(build.main, build.scalalib, build.testrunner, worker)
   def testTransitiveDeps = super.testTransitiveDeps() ++ Seq(worker.impl.testDep())
 
+  val x = 1
+  val y = 1
+  val z = 1
+  val z2 = 1
+  val z3 = 1
+  val z4 = 1
   def buildInfoPackageName = "mill.kotlinlib"
   def buildInfoObjectName = "Versions"
   def buildInfoMembers = Seq(
     BuildInfo.Value("kotlinVersion", build.Deps.kotlinVersion, "Version of Kotlin"),
+    BuildInfo.Value("kotlinVersion2", build.Deps.kotlinVersion, "Version of Kotlin"),
+    BuildInfo.Value("kotlinVersion3", build.Deps.kotlinVersion, "Version of Kotlin"),
+    BuildInfo.Value("kotlinVersion4", build.Deps.kotlinVersion, "Version of Kotlin"),
     BuildInfo.Value("koverVersion", build.Deps.RuntimeDeps.koverVersion, "Version of Kover."),
     BuildInfo.Value("ktfmtVersion", build.Deps.RuntimeDeps.ktfmt.version, "Version of Ktfmt."),
     BuildInfo.Value("ktlintVersion", build.Deps.RuntimeDeps.ktlint.version, "Version of ktlint."),
@@ -25,7 +34,6 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
     BuildInfo.Value("freemarkerDep", Dep.unparse(build.Deps.RuntimeDeps.freemarker).get, "freemarker dependency (used for Dokka)")
   )
 
-
   trait MillKotlinModule extends build.MillPublishScalaModule {
     override def javacOptions = {
       val release =
diff --git a/kotlinlib/worker/src/mill/kotlinlib/worker/api/KotlinWorker.scala b/kotlinlib/worker/src/mill/kotlinlib/worker/api/KotlinWorker.scala
index 112f8b19fc0..97f1f9ad4c3 100644
--- a/kotlinlib/worker/src/mill/kotlinlib/worker/api/KotlinWorker.scala
+++ b/kotlinlib/worker/src/mill/kotlinlib/worker/api/KotlinWorker.scala
@@ -10,7 +10,7 @@ import mill.api.{Ctx, Result}
 trait KotlinWorker {
 
   def compile(target: KotlinWorkerTarget, args: Seq[String])(implicit ctx: Ctx): Result[Unit]
-
+  val x = 1
 }
 
 sealed class KotlinWorkerTarget
diff --git a/main/codesig/src/Logger.scala b/main/codesig/src/Logger.scala
index c0a8e2a1038..d54c30edc9d 100644
--- a/main/codesig/src/Logger.scala
+++ b/main/codesig/src/Logger.scala
@@ -1,18 +1,23 @@
 package mill.codesig
 
-class Logger(logFolder: Option[os.Path]) {
+class Logger(mandatoryLogFolder: os.Path, logFolder: Option[os.Path]) {
   logFolder.foreach(os.remove.all(_))
+  os.remove.all(mandatoryLogFolder)
   private var count = 1
 
-  def log[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
+  def log0[T: upickle.default.Writer](p: os.Path, t: => sourcecode.Text[T], prefix: String = "") = {
     lazy val res = t
-    logFolder.foreach { p =>
-      os.write(
-        p / s"$count-$prefix${res.source}.json",
-        upickle.default.stream(res.value, indent = 4),
-        createFolders = true
-      )
-      count += 1
-    }
+    os.write(
+      p / s"$count-$prefix${res.source}.json",
+      upickle.default.stream(res.value, indent = 4),
+      createFolders = true
+    )
+    count += 1
+  }
+  def log[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
+    logFolder.foreach(log0(_, t, prefix))
+  }
+  def mandatoryLog[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
+    log0(mandatoryLogFolder, t, prefix)
   }
 }
diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index 9cf7d591b37..aa587b80e61 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -77,7 +77,7 @@ class CallGraphAnalysis(
     .collect { case (CallGraphAnalysis.LocalDef(d), v) => (d.toString, v) }
     .to(SortedMap)
 
-  logger.log(transitiveCallGraphHashes)
+  logger.mandatoryLog(transitiveCallGraphHashes)
 
   lazy val spanningInvalidationForest: Obj = prevTransitiveCallGraphHashesOpt() match {
     case Some(prevTransitiveCallGraphHashes) =>
@@ -90,7 +90,7 @@ class CallGraphAnalysis(
     case None => ujson.Obj()
   }
 
-  logger.log(spanningInvalidationForest)
+  logger.mandatoryLog(spanningInvalidationForest)
 }
 
 object CallGraphAnalysis {
@@ -131,11 +131,11 @@ object CallGraphAnalysis {
       .flatMap { case (vs, k) => vs.map((_, k)) }
       .groupMap(_._1)(_._2)
 
+    val reverseGraphEdges = indexGraphEdges.indices.map(reverseGraphMap.getOrElse(_, Array())).toArray
+    mill.main.client.DebugLog.println(pprint.apply(nodesWithChangedHashes).toString())
+    mill.main.client.DebugLog.println(pprint.apply(reverseGraphEdges).toString())
     SpanningForest.spanningTreeToJsonTree(
-      SpanningForest.apply(
-        indexGraphEdges.indices.map(reverseGraphMap(_)).toArray,
-        nodesWithChangedHashes
-      ),
+      SpanningForest.apply(reverseGraphEdges, nodesWithChangedHashes),
       k => indexToNodes(k).toString
     )
   }
diff --git a/main/codesig/test/src/Util.scala b/main/codesig/test/src/Util.scala
index 23b19eafbd5..503f1dfb3b6 100644
--- a/main/codesig/test/src/Util.scala
+++ b/main/codesig/test/src/Util.scala
@@ -19,7 +19,7 @@ object TestUtil {
           .map(os.Path(_))
       ),
       (_, _) => false,
-      new Logger(Some(testLogFolder)),
+      new Logger(testLogFolder, Some(testLogFolder)),
       () => None
     )
   }
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 814228f4790..d9d49cfb4fd 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -178,7 +178,10 @@ abstract class MillBuildRootModule()(implicit
 
           (isSimpleTarget && !isForwarderCallsite) || isCommand || isMillDiscover
         },
-        logger = new mill.codesig.Logger(Option.when(debugEnabled)(T.dest / "current")),
+        logger = new mill.codesig.Logger(
+          T.dest / "current",
+          Option.when(debugEnabled)(T.dest / "current")
+        ),
         prevTransitiveCallGraphHashesOpt = () =>
           Option.when(os.exists(T.dest / "previous/result.json"))(
             upickle.default.read[Map[String, Int]](

From 2b49d34f53c91e8860a48b3baf4854fe06a4d44f Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 11:15:10 +0800
Subject: [PATCH 08/13] .

---
 kotlinlib/package.mill                           |  3 +++
 main/codesig/src/Logger.scala                    |  7 +++----
 main/codesig/src/ReachabilityAnalysis.scala      | 11 ++++++-----
 .../test/src/{Util.scala => TestUtil.scala}      |  0
 main/eval/src/mill/eval/EvaluatorCore.scala      |  4 ++--
 main/util/src/mill/util/SpanningForest.scala     |  6 ++++--
 .../test/src/mill/util/SpanningForestTests.scala |  3 ++-
 runner/src/mill/runner/MillBuildRootModule.scala | 16 +++-------------
 8 files changed, 23 insertions(+), 27 deletions(-)
 rename main/codesig/test/src/{Util.scala => TestUtil.scala} (100%)

diff --git a/kotlinlib/package.mill b/kotlinlib/package.mill
index d714b916ce3..b3b148b29f5 100644
--- a/kotlinlib/package.mill
+++ b/kotlinlib/package.mill
@@ -18,6 +18,9 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
   val z2 = 1
   val z3 = 1
   val z4 = 1
+  val z5 = 1
+  val z6 = 1
+  val z7 = 7
   def buildInfoPackageName = "mill.kotlinlib"
   def buildInfoObjectName = "Versions"
   def buildInfoMembers = Seq(
diff --git a/main/codesig/src/Logger.scala b/main/codesig/src/Logger.scala
index d54c30edc9d..2c722a6c4eb 100644
--- a/main/codesig/src/Logger.scala
+++ b/main/codesig/src/Logger.scala
@@ -5,17 +5,16 @@ class Logger(mandatoryLogFolder: os.Path, logFolder: Option[os.Path]) {
   os.remove.all(mandatoryLogFolder)
   private var count = 1
 
-  def log0[T: upickle.default.Writer](p: os.Path, t: => sourcecode.Text[T], prefix: String = "") = {
-    lazy val res = t
+  def log0[T: upickle.default.Writer](p: os.Path, res: sourcecode.Text[T], prefix: String = "") = {
     os.write(
-      p / s"$count-$prefix${res.source}.json",
+      p / s"$prefix${res.source}.json",
       upickle.default.stream(res.value, indent = 4),
       createFolders = true
     )
     count += 1
   }
   def log[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
-    logFolder.foreach(log0(_, t, prefix))
+    logFolder.foreach(log0(_, t, s"$count-$prefix"))
   }
   def mandatoryLog[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
     log0(mandatoryLogFolder, t, prefix)
diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index aa587b80e61..74a5e41a8df 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -39,7 +39,7 @@ class CallGraphAnalysis(
   lazy val methodCodeHashes: SortedMap[String, Int] =
     methods.map { case (k, vs) => (k.toString, vs.codeHash) }.to(SortedMap)
 
-  logger.log(methodCodeHashes)
+  logger.mandatoryLog(methodCodeHashes)
 
   lazy val prettyCallGraph: SortedMap[String, Array[CallGraphAnalysis.Node]] = {
     indexGraphEdges.zip(indexToNodes).map { case (vs, k) =>
@@ -48,7 +48,7 @@ class CallGraphAnalysis(
       .to(SortedMap)
   }
 
-  logger.log(prettyCallGraph)
+  logger.mandatoryLog(prettyCallGraph)
 
   def transitiveCallGraphValues[V: scala.reflect.ClassTag](
       nodeValues: Array[V],
@@ -132,10 +132,11 @@ object CallGraphAnalysis {
       .groupMap(_._1)(_._2)
 
     val reverseGraphEdges = indexGraphEdges.indices.map(reverseGraphMap.getOrElse(_, Array())).toArray
-    mill.main.client.DebugLog.println(pprint.apply(nodesWithChangedHashes).toString())
-    mill.main.client.DebugLog.println(pprint.apply(reverseGraphEdges).toString())
+//    pprint.log(nodesWithChangedHashes)
+//    pprint.log(reverseGraphEdges)
+
     SpanningForest.spanningTreeToJsonTree(
-      SpanningForest.apply(reverseGraphEdges, nodesWithChangedHashes),
+      SpanningForest.apply(reverseGraphEdges, nodesWithChangedHashes, false),
       k => indexToNodes(k).toString
     )
   }
diff --git a/main/codesig/test/src/Util.scala b/main/codesig/test/src/TestUtil.scala
similarity index 100%
rename from main/codesig/test/src/Util.scala
rename to main/codesig/test/src/TestUtil.scala
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index 4be359f4e03..eeccaf7cd02 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -83,7 +83,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     os.write.over(
       outPath / OutFiles.millDependencyForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(upstreamIndexEdges, indexToTerminal.indices.toSet),
+        SpanningForest(upstreamIndexEdges, indexToTerminal.indices.toSet, true),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
@@ -288,7 +288,7 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     os.write.over(
       outPath / OutFiles.millInvalidationForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(downstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet),
+        SpanningForest(downstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet, true),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
diff --git a/main/util/src/mill/util/SpanningForest.scala b/main/util/src/mill/util/SpanningForest.scala
index bfd46878313..442fe0e36d9 100644
--- a/main/util/src/mill/util/SpanningForest.scala
+++ b/main/util/src/mill/util/SpanningForest.scala
@@ -19,7 +19,9 @@ private[mill] object SpanningForest {
     )
   }
   case class Node(values: mutable.Map[Int, Node] = mutable.Map())
-  def apply(indexGraphEdges: Array[Array[Int]], importantVertices: Set[Int]): Node = {
+  def apply(indexGraphEdges: Array[Array[Int]],
+            importantVertices: Set[Int],
+            limitToImportantVertices: Boolean): Node = {
     // Find all importantVertices which are "roots" with no incoming edges
     // from other importantVertices
     val destinations = importantVertices.flatMap(indexGraphEdges(_))
@@ -37,7 +39,7 @@ private[mill] object SpanningForest {
     breadthFirst(rootChangedNodeIndices) { index =>
       // needed to add explicit type for Scala 3.5.0-RC6
       val nextIndices = indexGraphEdges(index)
-        .filter(importantVertices)
+        .filter(e => !limitToImportantVertices || importantVertices(e))
 
       // We build up the spanningForest during a normal breadth first search,
       // using the `nodeMapping` to quickly find a vertice's tree node so we
diff --git a/main/util/test/src/mill/util/SpanningForestTests.scala b/main/util/test/src/mill/util/SpanningForestTests.scala
index a5e1de396c6..832620275f4 100644
--- a/main/util/test/src/mill/util/SpanningForestTests.scala
+++ b/main/util/test/src/mill/util/SpanningForestTests.scala
@@ -16,7 +16,8 @@ object SpanningForestTests extends TestSuite {
           Array(),
           Array(),
         ),
-        Set(0)
+        Set(0),
+        limitToImportantVertices = false
       )
 
       val expected =           Node(
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index d9d49cfb4fd..bea05d234f0 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -183,24 +183,14 @@ abstract class MillBuildRootModule()(implicit
           Option.when(debugEnabled)(T.dest / "current")
         ),
         prevTransitiveCallGraphHashesOpt = () =>
-          Option.when(os.exists(T.dest / "previous/result.json"))(
+          Option.when(os.exists(T.dest / "previous/transitiveCallGraphHashes.json"))(
             upickle.default.read[Map[String, Int]](
-              os.read.stream(T.dest / "previous/result.json")
+              os.read.stream(T.dest / "previous/transitiveCallGraphHashes.json")
             )
           )
       )
 
-    val result = codesig.transitiveCallGraphHashes
-    if (debugEnabled) {
-      os.write(
-        T.dest / "current/result.json",
-        upickle.default.stream(
-          SortedMap.from(codesig.transitiveCallGraphHashes0.map { case (k, v) => (k.toString, v) }),
-          indent = 4
-        )
-      )
-    }
-    result
+    codesig.transitiveCallGraphHashes
   }
 
   override def sources: T[Seq[PathRef]] = Task {

From 74820450eb5da4c66d788770b1d8e9d0ceb44aa1 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 18:30:35 +0800
Subject: [PATCH 09/13] fix spanningInvalidationForest.json

---
 example/javalib/basic/1-simple/build.mill        |  1 +
 main/codesig/src/ReachabilityAnalysis.scala      | 10 ++++------
 runner/src/mill/runner/MillBuildRootModule.scala |  4 ++--
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/example/javalib/basic/1-simple/build.mill b/example/javalib/basic/1-simple/build.mill
index 67abcd1e759..2bd2abad280 100644
--- a/example/javalib/basic/1-simple/build.mill
+++ b/example/javalib/basic/1-simple/build.mill
@@ -9,6 +9,7 @@ object foo extends JavaModule {
   )
 
   object test extends JavaTests with TestModule.Junit4 {
+    val x = 8
     def ivyDeps = super.ivyDeps() ++ Agg(
       ivy"com.google.guava:guava:33.3.0-jre"
     )
diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index 74a5e41a8df..b5ecaa30bc9 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -39,7 +39,7 @@ class CallGraphAnalysis(
   lazy val methodCodeHashes: SortedMap[String, Int] =
     methods.map { case (k, vs) => (k.toString, vs.codeHash) }.to(SortedMap)
 
-  logger.mandatoryLog(methodCodeHashes)
+  logger.log(methodCodeHashes)
 
   lazy val prettyCallGraph: SortedMap[String, Array[CallGraphAnalysis.Node]] = {
     indexGraphEdges.zip(indexToNodes).map { case (vs, k) =>
@@ -48,7 +48,7 @@ class CallGraphAnalysis(
       .to(SortedMap)
   }
 
-  logger.mandatoryLog(prettyCallGraph)
+  logger.log(prettyCallGraph)
 
   def transitiveCallGraphValues[V: scala.reflect.ClassTag](
       nodeValues: Array[V],
@@ -77,7 +77,8 @@ class CallGraphAnalysis(
     .collect { case (CallGraphAnalysis.LocalDef(d), v) => (d.toString, v) }
     .to(SortedMap)
 
-  logger.mandatoryLog(transitiveCallGraphHashes)
+  logger.mandatoryLog(transitiveCallGraphHashes0)
+  logger.log(transitiveCallGraphHashes)
 
   lazy val spanningInvalidationForest: Obj = prevTransitiveCallGraphHashesOpt() match {
     case Some(prevTransitiveCallGraphHashes) =>
@@ -121,7 +122,6 @@ object CallGraphAnalysis {
       .filter { nodeIndex =>
         val currentValue = transitiveCallGraphHashes0Map(indexToNodes(nodeIndex))
         val prevValue = prevTransitiveCallGraphHashes.get(indexToNodes(nodeIndex).toString)
-
         !prevValue.contains(currentValue)
       }
       .toSet
@@ -132,8 +132,6 @@ object CallGraphAnalysis {
       .groupMap(_._1)(_._2)
 
     val reverseGraphEdges = indexGraphEdges.indices.map(reverseGraphMap.getOrElse(_, Array())).toArray
-//    pprint.log(nodesWithChangedHashes)
-//    pprint.log(reverseGraphEdges)
 
     SpanningForest.spanningTreeToJsonTree(
       SpanningForest.apply(reverseGraphEdges, nodesWithChangedHashes, false),
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index bea05d234f0..3a2b793fe29 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -183,9 +183,9 @@ abstract class MillBuildRootModule()(implicit
           Option.when(debugEnabled)(T.dest / "current")
         ),
         prevTransitiveCallGraphHashesOpt = () =>
-          Option.when(os.exists(T.dest / "previous/transitiveCallGraphHashes.json"))(
+          Option.when(os.exists(T.dest / "previous/transitiveCallGraphHashes0.json"))(
             upickle.default.read[Map[String, Int]](
-              os.read.stream(T.dest / "previous/transitiveCallGraphHashes.json")
+              os.read.stream(T.dest / "previous/transitiveCallGraphHashes0.json")
             )
           )
       )

From 841a95b907ccb1534af3f91c979653cabf497b19 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 18:43:09 +0800
Subject: [PATCH 10/13] more consistently special case worker valueHash as
 inputHash

---
 example/javalib/basic/1-simple/build.mill     |  2 +-
 main/eval/src/mill/eval/EvaluatorCore.scala   |  3 +-
 main/eval/src/mill/eval/GroupEvaluator.scala  | 37 +++++++++----------
 main/eval/src/mill/eval/JsonArrayLogger.scala |  1 +
 4 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/example/javalib/basic/1-simple/build.mill b/example/javalib/basic/1-simple/build.mill
index 2bd2abad280..2fedbe96320 100644
--- a/example/javalib/basic/1-simple/build.mill
+++ b/example/javalib/basic/1-simple/build.mill
@@ -9,7 +9,7 @@ object foo extends JavaModule {
   )
 
   object test extends JavaTests with TestModule.Junit4 {
-    val x = 8
+    val x = 81
     def ivyDeps = super.ivyDeps() ++ Agg(
       ivy"com.google.guava:guava:33.3.0-jre"
     )
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index eeccaf7cd02..6054402e74c 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -206,13 +206,14 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
                 cached = res.cached
               )
               if (!res.cached) uncached.put(terminal, ())
-              if (res.changedValueHash) changedValueHash.put(terminal, ())
+              if (res.valueHashChanged) changedValueHash.put(terminal, ())
 
               profileLogger.log(
                 ProfileLogger.Timing(
                   terminal.render,
                   (duration / 1000).toInt,
                   res.cached,
+                  res.valueHashChanged,
                   deps.map(_.render),
                   res.inputsHash,
                   res.previousInputsHash
diff --git a/main/eval/src/mill/eval/GroupEvaluator.scala b/main/eval/src/mill/eval/GroupEvaluator.scala
index 11bff00d26e..476224d4ee9 100644
--- a/main/eval/src/mill/eval/GroupEvaluator.scala
+++ b/main/eval/src/mill/eval/GroupEvaluator.scala
@@ -103,17 +103,14 @@ private[mill] trait GroupEvaluator {
             executionContext,
             exclusive
           )
-          GroupEvaluator.Results(newResults, newEvaluated.toSeq, null, inputsHash, -1, changedValueHash = false)
+          GroupEvaluator.Results(newResults, newEvaluated.toSeq, null, inputsHash, -1, valueHashChanged = false)
 
         case labelled: Terminal.Labelled[_] =>
           val out =
             if (!labelled.task.ctx.external) outPath
             else externalOutPath
 
-          val paths = EvaluatorPaths.resolveDestPaths(
-            out,
-            Terminal.destSegments(labelled)
-          )
+          val paths = EvaluatorPaths.resolveDestPaths(out, Terminal.destSegments(labelled))
 
           val cached = loadCachedJson(logger, inputsHash, labelled, paths)
 
@@ -121,9 +118,8 @@ private[mill] trait GroupEvaluator {
             logger,
             inputsHash,
             labelled,
-            forceDiscard =
-              // worker metadata file removed by user, let's recompute the worker
-              cached.isEmpty
+            // worker metadata file removed by user, let's recompute the worker
+            forceDiscard = cached.isEmpty
           )
 
           upToDateWorker.map((_, inputsHash)) orElse cached.flatMap { case (inputHash, valOpt, valueHash) => valOpt.map((_, valueHash))} match {
@@ -138,7 +134,7 @@ private[mill] trait GroupEvaluator {
                 cached = true,
                 inputsHash,
                 -1,
-                changedValueHash = false
+                valueHashChanged = false
               )
 
             case _ =>
@@ -161,14 +157,17 @@ private[mill] trait GroupEvaluator {
                   exclusive
                 )
 
+
               val valueHash = newResults(labelled.task) match {
                 case TaskResult(Result.Failure(_, Some((v, _))), _) =>
-                  handleTaskResult(v, v.##, paths.meta, inputsHash, labelled)
-                  v.##
+                  val valueHash = if (terminal.task.asWorker.isEmpty) v.## else inputsHash
+                  handleTaskResult(v, valueHash, paths.meta, inputsHash, labelled)
+
 
                 case TaskResult(Result.Success((v, _)), _) =>
-                  handleTaskResult(v, v.##, paths.meta, inputsHash, labelled)
-                  v.##
+                  val valueHash = if (terminal.task.asWorker.isEmpty) v.## else inputsHash
+                  handleTaskResult(v, valueHash, paths.meta, inputsHash, labelled)
+                  valueHash
 
                 case _ =>
                   // Wipe out any cached meta.json file that exists, so
@@ -459,11 +458,11 @@ private[mill] trait GroupEvaluator {
 private[mill] object GroupEvaluator {
 
   case class Results(
-      newResults: Map[Task[_], TaskResult[(Val, Int)]],
-      newEvaluated: Seq[Task[_]],
-      cached: java.lang.Boolean,
-      inputsHash: Int,
-      previousInputsHash: Int,
-      changedValueHash: Boolean
+                      newResults: Map[Task[_], TaskResult[(Val, Int)]],
+                      newEvaluated: Seq[Task[_]],
+                      cached: java.lang.Boolean,
+                      inputsHash: Int,
+                      previousInputsHash: Int,
+                      valueHashChanged: Boolean
   )
 }
diff --git a/main/eval/src/mill/eval/JsonArrayLogger.scala b/main/eval/src/mill/eval/JsonArrayLogger.scala
index 87292aef7bd..209c82e4e9d 100644
--- a/main/eval/src/mill/eval/JsonArrayLogger.scala
+++ b/main/eval/src/mill/eval/JsonArrayLogger.scala
@@ -43,6 +43,7 @@ private object ProfileLogger {
       label: String,
       millis: Int,
       cached: java.lang.Boolean = null,
+      valueHashChanged: java.lang.Boolean = null,
       dependencies: Seq[String] = Nil,
       inputsHash: Int,
       previousInputsHash: Int = -1

From d90facc14b7bdb120f2b92c62e5f843ba000ced5 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 19:02:20 +0800
Subject: [PATCH 11/13] .

---
 example/javalib/basic/1-simple/build.mill | 1 -
 kotlinlib/package.mill                    | 9 ---------
 2 files changed, 10 deletions(-)

diff --git a/example/javalib/basic/1-simple/build.mill b/example/javalib/basic/1-simple/build.mill
index 2fedbe96320..67abcd1e759 100644
--- a/example/javalib/basic/1-simple/build.mill
+++ b/example/javalib/basic/1-simple/build.mill
@@ -9,7 +9,6 @@ object foo extends JavaModule {
   )
 
   object test extends JavaTests with TestModule.Junit4 {
-    val x = 81
     def ivyDeps = super.ivyDeps() ++ Agg(
       ivy"com.google.guava:guava:33.3.0-jre"
     )
diff --git a/kotlinlib/package.mill b/kotlinlib/package.mill
index b3b148b29f5..2913cb65eb2 100644
--- a/kotlinlib/package.mill
+++ b/kotlinlib/package.mill
@@ -12,15 +12,6 @@ object `package` extends RootModule with build.MillPublishScalaModule with Build
   def moduleDeps = Seq(build.main, build.scalalib, build.testrunner, worker)
   def testTransitiveDeps = super.testTransitiveDeps() ++ Seq(worker.impl.testDep())
 
-  val x = 1
-  val y = 1
-  val z = 1
-  val z2 = 1
-  val z3 = 1
-  val z4 = 1
-  val z5 = 1
-  val z6 = 1
-  val z7 = 7
   def buildInfoPackageName = "mill.kotlinlib"
   def buildInfoObjectName = "Versions"
   def buildInfoMembers = Seq(

From 1273d3ec23857f4b15a391ac75c61a07c1bd5128 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 19:05:27 +0800
Subject: [PATCH 12/13] .

---
 main/codesig/src/Logger.scala                 |  5 +++-
 main/codesig/src/ReachabilityAnalysis.scala   |  3 ++-
 main/eval/src/mill/eval/EvaluatorCore.scala   | 16 ++++++-----
 main/eval/src/mill/eval/GroupEvaluator.scala  | 27 ++++++++++++-------
 main/util/src/mill/util/SpanningForest.scala  |  8 +++---
 .../src/mill/util/SpanningForestTests.scala   |  7 +++--
 6 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/main/codesig/src/Logger.scala b/main/codesig/src/Logger.scala
index 2c722a6c4eb..315f2475124 100644
--- a/main/codesig/src/Logger.scala
+++ b/main/codesig/src/Logger.scala
@@ -16,7 +16,10 @@ class Logger(mandatoryLogFolder: os.Path, logFolder: Option[os.Path]) {
   def log[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
     logFolder.foreach(log0(_, t, s"$count-$prefix"))
   }
-  def mandatoryLog[T: upickle.default.Writer](t: => sourcecode.Text[T], prefix: String = ""): Unit = {
+  def mandatoryLog[T: upickle.default.Writer](
+      t: => sourcecode.Text[T],
+      prefix: String = ""
+  ): Unit = {
     log0(mandatoryLogFolder, t, prefix)
   }
 }
diff --git a/main/codesig/src/ReachabilityAnalysis.scala b/main/codesig/src/ReachabilityAnalysis.scala
index b5ecaa30bc9..f58c2fcf6ea 100644
--- a/main/codesig/src/ReachabilityAnalysis.scala
+++ b/main/codesig/src/ReachabilityAnalysis.scala
@@ -131,7 +131,8 @@ object CallGraphAnalysis {
       .flatMap { case (vs, k) => vs.map((_, k)) }
       .groupMap(_._1)(_._2)
 
-    val reverseGraphEdges = indexGraphEdges.indices.map(reverseGraphMap.getOrElse(_, Array())).toArray
+    val reverseGraphEdges =
+      indexGraphEdges.indices.map(reverseGraphMap.getOrElse(_, Array())).toArray
 
     SpanningForest.spanningTreeToJsonTree(
       SpanningForest.apply(reverseGraphEdges, nodesWithChangedHashes, false),
diff --git a/main/eval/src/mill/eval/EvaluatorCore.scala b/main/eval/src/mill/eval/EvaluatorCore.scala
index 6054402e74c..62215659950 100644
--- a/main/eval/src/mill/eval/EvaluatorCore.scala
+++ b/main/eval/src/mill/eval/EvaluatorCore.scala
@@ -79,7 +79,8 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
     val count = new AtomicInteger(1)
     val indexToTerminal = sortedGroups.keys().toArray
     val terminalToIndex = indexToTerminal.zipWithIndex.toMap
-    val upstreamIndexEdges = indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
+    val upstreamIndexEdges =
+      indexToTerminal.map(t => interGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray)
     os.write.over(
       outPath / OutFiles.millDependencyForest,
       SpanningForest.spanningTreeToJsonTree(
@@ -273,23 +274,26 @@ private[mill] trait EvaluatorCore extends GroupEvaluator {
 
     val reverseInterGroupDeps = interGroupDeps
       .iterator
-      .flatMap{case (k, vs) => vs.map(_ -> k)}
+      .flatMap { case (k, vs) => vs.map(_ -> k) }
       .toSeq
       .groupMap(_._1)(_._2)
 
-
     val changedTerminalIndices = changedValueHash.keys().asScala.toSet
     val downstreamIndexEdges = indexToTerminal
       .map(t =>
-        if (changedTerminalIndices(t)) reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray
+        if (changedTerminalIndices(t))
+          reverseInterGroupDeps.getOrElse(t, Nil).map(terminalToIndex).toArray
         else Array.empty[Int]
       )
 
-
     os.write.over(
       outPath / OutFiles.millInvalidationForest,
       SpanningForest.spanningTreeToJsonTree(
-        SpanningForest(downstreamIndexEdges, uncached.keys().asScala.map(terminalToIndex).toSet, true),
+        SpanningForest(
+          downstreamIndexEdges,
+          uncached.keys().asScala.map(terminalToIndex).toSet,
+          true
+        ),
         i => indexToTerminal(i).render
       ).render(indent = 2)
     )
diff --git a/main/eval/src/mill/eval/GroupEvaluator.scala b/main/eval/src/mill/eval/GroupEvaluator.scala
index 476224d4ee9..ec8a064324a 100644
--- a/main/eval/src/mill/eval/GroupEvaluator.scala
+++ b/main/eval/src/mill/eval/GroupEvaluator.scala
@@ -103,7 +103,14 @@ private[mill] trait GroupEvaluator {
             executionContext,
             exclusive
           )
-          GroupEvaluator.Results(newResults, newEvaluated.toSeq, null, inputsHash, -1, valueHashChanged = false)
+          GroupEvaluator.Results(
+            newResults,
+            newEvaluated.toSeq,
+            null,
+            inputsHash,
+            -1,
+            valueHashChanged = false
+          )
 
         case labelled: Terminal.Labelled[_] =>
           val out =
@@ -122,7 +129,9 @@ private[mill] trait GroupEvaluator {
             forceDiscard = cached.isEmpty
           )
 
-          upToDateWorker.map((_, inputsHash)) orElse cached.flatMap { case (inputHash, valOpt, valueHash) => valOpt.map((_, valueHash))} match {
+          upToDateWorker.map((_, inputsHash)) orElse cached.flatMap {
+            case (inputHash, valOpt, valueHash) => valOpt.map((_, valueHash))
+          } match {
             case Some((v, hashCode)) =>
               val res = Result.Success((v, hashCode))
               val newResults: Map[Task[_], TaskResult[(Val, Int)]] =
@@ -157,13 +166,11 @@ private[mill] trait GroupEvaluator {
                   exclusive
                 )
 
-
               val valueHash = newResults(labelled.task) match {
                 case TaskResult(Result.Failure(_, Some((v, _))), _) =>
                   val valueHash = if (terminal.task.asWorker.isEmpty) v.## else inputsHash
                   handleTaskResult(v, valueHash, paths.meta, inputsHash, labelled)
 
-
                 case TaskResult(Result.Success((v, _)), _) =>
                   val valueHash = if (terminal.task.asWorker.isEmpty) v.## else inputsHash
                   handleTaskResult(v, valueHash, paths.meta, inputsHash, labelled)
@@ -458,11 +465,11 @@ private[mill] trait GroupEvaluator {
 private[mill] object GroupEvaluator {
 
   case class Results(
-                      newResults: Map[Task[_], TaskResult[(Val, Int)]],
-                      newEvaluated: Seq[Task[_]],
-                      cached: java.lang.Boolean,
-                      inputsHash: Int,
-                      previousInputsHash: Int,
-                      valueHashChanged: Boolean
+      newResults: Map[Task[_], TaskResult[(Val, Int)]],
+      newEvaluated: Seq[Task[_]],
+      cached: java.lang.Boolean,
+      inputsHash: Int,
+      previousInputsHash: Int,
+      valueHashChanged: Boolean
   )
 }
diff --git a/main/util/src/mill/util/SpanningForest.scala b/main/util/src/mill/util/SpanningForest.scala
index 442fe0e36d9..2627d12a0c9 100644
--- a/main/util/src/mill/util/SpanningForest.scala
+++ b/main/util/src/mill/util/SpanningForest.scala
@@ -19,9 +19,11 @@ private[mill] object SpanningForest {
     )
   }
   case class Node(values: mutable.Map[Int, Node] = mutable.Map())
-  def apply(indexGraphEdges: Array[Array[Int]],
-            importantVertices: Set[Int],
-            limitToImportantVertices: Boolean): Node = {
+  def apply(
+      indexGraphEdges: Array[Array[Int]],
+      importantVertices: Set[Int],
+      limitToImportantVertices: Boolean
+  ): Node = {
     // Find all importantVertices which are "roots" with no incoming edges
     // from other importantVertices
     val destinations = importantVertices.flatMap(indexGraphEdges(_))
diff --git a/main/util/test/src/mill/util/SpanningForestTests.scala b/main/util/test/src/mill/util/SpanningForestTests.scala
index 832620275f4..afab8147a49 100644
--- a/main/util/test/src/mill/util/SpanningForestTests.scala
+++ b/main/util/test/src/mill/util/SpanningForestTests.scala
@@ -14,13 +14,13 @@ object SpanningForestTests extends TestSuite {
           Array(2),
           Array(3),
           Array(),
-          Array(),
+          Array()
         ),
         Set(0),
         limitToImportantVertices = false
       )
 
-      val expected =           Node(
+      val expected = Node(
         mutable.Map(
           0 -> Node(
             mutable.Map(
@@ -38,8 +38,7 @@ object SpanningForestTests extends TestSuite {
         )
       )
 
-      assert(forest == expected
-      )
+      assert(forest == expected)
     }
 
   }

From 281cabdaa75c80f4f468539ca18867bbcde2b202 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 15 Dec 2024 19:20:28 +0800
Subject: [PATCH 13/13] .

---
 main/codesig/src/Logger.scala                    | 6 +++++-
 runner/src/mill/runner/MillBuildRootModule.scala | 1 -
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/main/codesig/src/Logger.scala b/main/codesig/src/Logger.scala
index 315f2475124..b30de439433 100644
--- a/main/codesig/src/Logger.scala
+++ b/main/codesig/src/Logger.scala
@@ -5,7 +5,11 @@ class Logger(mandatoryLogFolder: os.Path, logFolder: Option[os.Path]) {
   os.remove.all(mandatoryLogFolder)
   private var count = 1
 
-  def log0[T: upickle.default.Writer](p: os.Path, res: sourcecode.Text[T], prefix: String = "") = {
+  def log0[T: upickle.default.Writer](
+      p: os.Path,
+      res: sourcecode.Text[T],
+      prefix: String = ""
+  ): Unit = {
     os.write(
       p / s"$prefix${res.source}.json",
       upickle.default.stream(res.value, indent = 4),
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 3a2b793fe29..e36732bca6c 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -12,7 +12,6 @@ import mill.main.client.OutFiles._
 import mill.main.client.CodeGenConstants.buildFileExtensions
 import mill.main.{BuildInfo, RootModule}
 
-import scala.collection.immutable.SortedMap
 import scala.util.Try
 import mill.define.Target