better versioning pipeline

VERSIONS.md

@@ -124,6 +124,7 @@ Thanks to Dave Cottlehuber @dch for testing.
 
 ## 0.12.0
 - breakout `zig.get` into its own package to prevent dependency problems.
+- versioning of .so files should track the version.  This feature should be considered experimental.
 
 ## Upcoming
 - `precompiled` mode that will let you obtain packages with precompiled assets.

lib/zig/builder.ex

@@ -27,8 +27,7 @@ defmodule Zig.Builder do
 
     assigns = %{
       module: module.module,
-      # TODO: fix this version setting!
-      version: Version.parse!("0.0.0"),
+      version: module.version,
       beam_dir: Path.join(:code.priv_dir(:zigler), "beam"),
       link_lib: module.link_lib,
       include_dir: module.include_dir,

lib/zig/module.ex

@@ -31,6 +31,7 @@ defmodule Zig.Module do
                 :manifest_module,
                 :sema,
                 :parsed,
+                :version,
                 language: Elixir,
                 nifs: [],
                 ignore: [],
@@ -59,6 +60,9 @@ defmodule Zig.Module do
           base_code_path: nil | Path.t(),
           manifest: nil | Manifest.t(),
           manifest_module: nil | module(),
+          sema: Sema.t(),
+          parsed: Parser.t(),
+          version: String.t(),
           language: Elixir | :erlang,
           nifs: nif_opts() | [Nif.t()],
           ignore: [atom()],
@@ -132,6 +136,7 @@ defmodule Zig.Module do
 
   defp normalize_options(opts) do
     opts
+    |> obtain_version
     # |> normalize_nifs
     # |> normalize_libs
     # |> normalize_build_opts
@@ -140,6 +145,26 @@ defmodule Zig.Module do
     # |> EasyC.normalize_aliasing()
   end
 
+  defp obtain_version(opts) do
+    otp_app = Keyword.fetch!(opts, :otp_app)  
+    Keyword.put_new_lazy(opts, :version, fn ->
+      cond do
+        # try checking the mix project first (this is if the project is being compiled for the first time)
+        function_exported?(Mix.Project, :config, 0) ->
+          Mix.Project.config()
+          |> Keyword.fetch!(:version)
+          |> Version.parse!()
+        # try checking the application version (this is if we are hot-patching the so file)
+        tuple = Application.loaded_applications()[otp_app] ->
+          tuple
+          |> elem(2)
+          |> Version.parse!()
+        :else ->
+          Version.parse!("0.0.0")
+      end
+    end)
+  end
+
   # defp normalize_nifs(opts) do
   #  Keyword.update!(opts, :nifs, fn
   #    {:auto, opts} ->