fix: do not generate a modulemap for Objc targets, if they provide one (

#710)

The goal of this PR is to selectively generate modulemap files for ObjC
targets. If an ObjC target provides a modulemap, we will not generate a
modulemap. This avoids `redefinition of module` errors when running
outside of the Bazel action sandbox. While we may not generate
modulemaps for some ObjC targets, we must continue to create the
`generate_modulemap` targets. The logic that assigns dependencies has no
way to know whether a modulemap target has been generated (i.e., the
ObjC target may be a dependency in another Swift package). Hence,
`generate_modulemap` has been modified to have a noop mode.

- Add `noop` attribute to `generate_modulemap` rule. If `True`, a
modulemap is generated and the appropriate providers are populated. If
`False, a modulemap is not generated and empty providers are returned.
- Update `clang_files.collect_files()` to return the path of the
modulemap file, if one is found.
- Update the build file generation to set the `noop` attribute for
`generate_modulemap` based upon whether a modulemap file was found for
the module.
- Update `firebase_example` to use `rules_xcodeproj` to generate an
Xcode project and ensure that it builds using the `rules_xcodeproj`
recommended build API>


Related to
MobileNativeFoundation/rules_xcodeproj#2703.
Closes #712.

docs/internal_rules_and_macros_overview.md

@@ -17,7 +17,7 @@ On this page:
 ## generate_modulemap
 
 <pre>
-generate_modulemap(<a href="#generate_modulemap-name">name</a>, <a href="#generate_modulemap-deps">deps</a>, <a href="#generate_modulemap-hdrs">hdrs</a>, <a href="#generate_modulemap-module_name">module_name</a>)
+generate_modulemap(<a href="#generate_modulemap-name">name</a>, <a href="#generate_modulemap-deps">deps</a>, <a href="#generate_modulemap-hdrs">hdrs</a>, <a href="#generate_modulemap-module_name">module_name</a>, <a href="#generate_modulemap-noop">noop</a>)
 </pre>
 
 Generate a modulemap for an Objective-C module.
@@ -31,6 +31,7 @@ Generate a modulemap for an Objective-C module.
 | <a id="generate_modulemap-deps"></a>deps |  The module maps that this module uses.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
 | <a id="generate_modulemap-hdrs"></a>hdrs |  The public headers for this module.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | required |  |
 | <a id="generate_modulemap-module_name"></a>module_name |  The name of the module.   | String | optional | <code>""</code> |
+| <a id="generate_modulemap-noop"></a>noop |  Designates whether a modulemap should be generated. If <code>False</code>, a modulemap is generated. If <code>True</code>, a modulemap file is not generated and the returned providers are empty.   | Boolean | optional | <code>False</code> |
 
 
 <a id="resource_bundle_accessor"></a>

examples/firebase_example/MODULE.bazel

@@ -24,6 +24,11 @@ bazel_dep(
     repo_name = "build_bazel_rules_apple",
 )
 
+bazel_dep(
+    name = "rules_xcodeproj",
+    version = "1.12.1",
+    dev_dependency = True,
+)
 bazel_dep(
     name = "bazel_skylib_gazelle_plugin",
     version = "1.4.2",

examples/firebase_example/analytics/AnalyticsExample/BUILD.bazel

@@ -1,6 +1,10 @@
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
 load("@build_bazel_rules_apple//apple:ios.bzl", "ios_application")
 load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
+load(
+    "@rules_xcodeproj//xcodeproj:defs.bzl",
+    "xcodeproj",
+)
 
 swift_library(
     name = "AnalyticsExample",
@@ -27,6 +31,7 @@ ios_application(
     infoplists = [":Info.plist"],
     launch_storyboard = "//analytics/AnalyticsExample:Base.lproj/LaunchScreen.storyboard",
     minimum_os_version = "13.0",
+    visibility = ["//visibility:public"],
     deps = [":AnalyticsExample"],
 )
 
@@ -36,3 +41,12 @@ build_test(
         ":iosapp",
     ],
 )
+
+xcodeproj(
+    name = "xcodeproj",
+    project_name = "AnalyticsExample",
+    tags = ["manual"],
+    top_level_targets = [
+        ":iosapp",
+    ],
+)

examples/firebase_example/do_test

@@ -20,3 +20,16 @@ assert_match() {
 
 # Ensure that it builds and tests pass
 "${bazel}" test //...
+
+# The analytics/AnalyticsExample generates an Xcode project using
+# rules_xcodeproj. The following ensures that the project generates properly
+# and that the project builds as rules_xcodeproj executes the build.
+# Related:
+# https://github.com/MobileNativeFoundation/rules_xcodeproj/issues/2703
+
+# Generate the Xcode project
+"${bazel}" run //analytics/AnalyticsExample:xcodeproj
+
+# Build the workspace
+"${bazel}" run //analytics/AnalyticsExample:xcodeproj -- \
+  --generator_output_groups=all_targets 'build --remote_download_minimal'

swiftpkg/internal/generate_modulemap.bzl

@@ -18,10 +18,33 @@ ModuleMapInfo = provider(
 
 def _generate_modulemap_impl(ctx):
     module_name = ctx.attr.module_name
+
+    # Decide whether we should generate the modulemap. If we do not generate
+    # the modulemap, we still need to return expected providers.
+    if ctx.attr.noop:
+        return [
+            DefaultInfo(files = depset([])),
+            ModuleMapInfo(
+                module_name = module_name,
+                modulemap_file = None,
+            ),
+            apple_common.new_objc_provider(
+                module_map = depset([]),
+            ),
+            CcInfo(
+                compilation_context = cc_common.create_compilation_context(
+                    headers = depset([]),
+                    includes = depset([]),
+                ),
+            ),
+        ]
+
     uses = [
         dep[ModuleMapInfo].module_name
         for dep in ctx.attr.deps
+        if ModuleMapInfo in dep
     ]
+
     out_filename = "{}/module.modulemap".format(module_name)
     modulemap_file = ctx.actions.declare_file(out_filename)
 
@@ -75,6 +98,14 @@ generate_modulemap = rule(
         "module_name": attr.string(
             doc = "The name of the module.",
         ),
+        "noop": attr.bool(
+            doc = """\
+Designates whether a modulemap should be generated. If `False`, a modulemap is \
+generated. If `True`, a modulemap file is not generated and the returned \
+providers are empty.\
+""",
+            default = False,
+        ),
     },
     doc = "Generate a modulemap for an Objective-C module.",
 )

swiftpkg/internal/pkginfos.bzl

@@ -972,6 +972,7 @@ def _new_clang_src_info_from_sources(
         textual_hdrs = textual_hdrs,
         public_includes = public_includes,
         private_includes = private_includes,
+        modulemap_path = organized_files.modulemap,
     )
 
 def _new_clang_src_info(
@@ -980,14 +981,16 @@ def _new_clang_src_info(
         hdrs = [],
         textual_hdrs = [],
         public_includes = [],
-        private_includes = []):
+        private_includes = [],
+        modulemap_path = None):
     return struct(
         srcs = srcs,
         explicit_srcs = explicit_srcs,
         hdrs = hdrs,
         textual_hdrs = textual_hdrs,
         public_includes = public_includes,
         private_includes = private_includes,
+        modulemap_path = modulemap_path,
     )
 
 # MARK: - Objc Source Info

swiftpkg/internal/swiftpkg_build_files.bzl

@@ -321,27 +321,34 @@ def _clang_target_build_file(repository_ctx, pkg_ctx, target):
             sdk_framework_bzl_selects,
         )
 
-        modulemap_deps = _collect_modulemap_deps(deps)
-
         # There is a known issue with Objective-C library targets not
         # supporting the `@import` of modules defined in other Objective-C
         # targets. As a workaround, we will define two targets. One is the
         # `objc_library` target.  The other is a `generate_modulemap`
         # target. This second target generates a `module.modulemap` file and
         # provides information about that generated file to `objc_library`
-        # targets.
+        # targets, if `noop` is `False`. If `noop` is `True`, the target
+        # generates nothing and returns "empty" providers.
+        #
+        # Why not skip adding the `generate_modulemap` if `noop` is `True`?
+        # The logic that assigns dependencies for other targets has no way to
+        # know whether the modulemap target exists. Hence, we ensure that it
+        # always exists but does nothing.
         #
         # See `deps_indexes.bzl` for the logic that resolves the dependency
         # labels.
         # See `generate_modulemap.bzl` for details on the modulemap generation.
         # See `//swiftpkg/tests/generate_modulemap_tests` package for a usage
         # example.
+        modulemap_deps = _collect_modulemap_deps(deps)
         load_stmts = [swiftpkg_generate_modulemap_load_stmt]
         modulemap_target_name = pkginfo_targets.modulemap_label_name(bzl_target_name)
+        noop_modulemap = clang_src_info.modulemap_path != None
         modulemap_attrs = {
             "deps": bzl_selects.to_starlark(modulemap_deps),
             "hdrs": clang_src_info.hdrs,
             "module_name": target.c99name,
+            "noop": noop_modulemap,
             "visibility": ["//visibility:public"],
         }
         decls = [

swiftpkg/tests/swiftpkg_build_files_tests.bzl

@@ -283,6 +283,47 @@ _pkg_info = pkginfos.new(
                 ],
             ),
         ),
+        pkginfos.new_target(
+            name = "ObjcLibraryWithModulemap",
+            type = "regular",
+            c99name = "ObjcLibraryWithModulemap",
+            module_type = "ClangTarget",
+            path = ".",
+            # NOTE: SPM does not report header files in the sources for clang
+            # targets. The `swift_package` code reads the filesystem to find
+            # the sources.
+            sources = [
+                "src/foo.m",
+                "src/foo.h",
+            ],
+            source_paths = [
+                "src/",
+            ],
+            public_hdrs_path = "include",
+            dependencies = [
+                pkginfos.new_target_dependency(
+                    by_name = pkginfos.new_by_name_reference("ObjcLibraryDep"),
+                ),
+            ],
+            repo_name = _repo_name,
+            clang_src_info = pkginfos.new_clang_src_info(
+                hdrs = ["include/external.h"],
+                srcs = [
+                    "src/foo.h",
+                    "src/foo.m",
+                ],
+                public_includes = ["include"],
+                private_includes = ["src"],
+                textual_hdrs = ["src/foo.m"],
+                modulemap_path = "include/module.modulemap",
+            ),
+            objc_src_info = pkginfos.new_objc_src_info(
+                builtin_frameworks = [
+                    "Foundation",
+                    "UIKit",
+                ],
+            ),
+        ),
         pkginfos.new_target(
             name = "SwiftLibraryWithConditionalDep",
             type = "regular",
@@ -490,6 +531,14 @@ _deps_index_json = """
             "package_identity": "mypackage",
             "product_memberships": []
         },
+        {
+            "name": "ObjcLibraryWithModulemap",
+            "c99name": "ObjcLibraryWithModulemap",
+            "src_type": "objc",
+            "label": "@swiftpkg_mypackage//:ObjcLibraryWithModulemap",
+            "package_identity": "mypackage",
+            "product_memberships": []
+        },
         {
             "name": "SwiftLibraryWithConditionalDep",
             "c99name": "SwiftLibraryWithConditionalDep",
@@ -679,6 +728,7 @@ generate_modulemap(
     deps = ["@swiftpkg_mypackage//:ObjcLibraryDep_modulemap"],
     hdrs = ["include/external.h"],
     module_name = "ObjcLibrary",
+    noop = False,
     visibility = ["//visibility:public"],
 )
 
@@ -724,6 +774,65 @@ objc_library(
     textual_hdrs = ["src/foo.m"],
     visibility = ["//visibility:public"],
 )
+""",
+        ),
+        struct(
+            msg = "Objc target with a modulemap",
+            name = "ObjcLibraryWithModulemap",
+            exp = """\
+load("@rules_swift_package_manager//swiftpkg:build_defs.bzl", "generate_modulemap")
+
+generate_modulemap(
+    name = "ObjcLibraryWithModulemap_modulemap",
+    deps = ["@swiftpkg_mypackage//:ObjcLibraryDep_modulemap"],
+    hdrs = ["include/external.h"],
+    module_name = "ObjcLibraryWithModulemap",
+    noop = True,
+    visibility = ["//visibility:public"],
+)
+
+objc_library(
+    name = "ObjcLibraryWithModulemap",
+    copts = [
+        "-fblocks",
+        "-fobjc-arc",
+        "-fPIC",
+        "-fmodule-name=ObjcLibraryWithModulemap",
+        "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
+    ],
+    defines = ["SWIFT_PACKAGE=1"],
+    deps = [
+        "@swiftpkg_mypackage//:ObjcLibraryDep",
+        "@swiftpkg_mypackage//:ObjcLibraryDep_modulemap",
+    ],
+    enable_modules = True,
+    hdrs = ["include/external.h"],
+    includes = ["include"],
+    module_name = "ObjcLibraryWithModulemap",
+    sdk_frameworks = select({
+        "@rules_swift_package_manager//config_settings/spm/platform:ios": [
+            "Foundation",
+            "UIKit",
+        ],
+        "@rules_swift_package_manager//config_settings/spm/platform:macos": ["Foundation"],
+        "@rules_swift_package_manager//config_settings/spm/platform:tvos": [
+            "Foundation",
+            "UIKit",
+        ],
+        "@rules_swift_package_manager//config_settings/spm/platform:watchos": [
+            "Foundation",
+            "UIKit",
+        ],
+        "//conditions:default": [],
+    }),
+    srcs = [
+        "src/foo.h",
+        "src/foo.m",
+    ],
+    tags = ["swift_module=ObjcLibraryWithModulemap"],
+    textual_hdrs = ["src/foo.m"],
+    visibility = ["//visibility:public"],
+)
 """,
         ),
         struct(
@@ -870,6 +979,7 @@ generate_modulemap(
     deps = [],
     hdrs = ["include/external.h"],
     module_name = "ObjcLibraryWithResources",
+    noop = False,
     visibility = ["//visibility:public"],
 )