Allow apps to be selected in umbrella projects

Closes #1731
Closes #1730

Author: José Valim

CHANGELOG.md

@@ -4,6 +4,7 @@
   * [Enum] Add `Enum.take_every/2`
   * [IEx] IEx now respects signals sent from the Ctrl+G menu
   * [Kernel] Allow documentation for types with `@typedoc`
+  * [Mix] Allow apps to be selected in umbrella projects
   * [Stream] Add `Stream.unfold/1`
 
 * Bug fixes

lib/mix/lib/mix/project.ex

@@ -141,27 +141,37 @@ defmodule Mix.Project do
   def recur(post_config // [], fun) do
     if apps_path = config[:apps_path] do
       paths = Path.wildcard(Path.join(apps_path, "*"))
-      paths = Enum.filter(paths, &File.dir?(&1))
 
-      projects = Enum.map paths, fn path ->
-        dir = Path.basename(path)
-        app = dir |> String.downcase |> binary_to_atom
-        { app, path }
-      end
-
-      projects = topsort_projects(projects, Path.expand(apps_path))
-
-      results = Enum.map projects, fn { app, app_path } ->
-        in_project(app, app_path, post_config, fun)
-      end
-
-      results
+      paths
+      |> Enum.filter(&File.dir?(&1))
+      |> extract_projects
+      |> filter_projects(config[:apps])
+      |> topsort_projects(Path.expand(apps_path))
+      |> recur_projects(post_config, fun)
     else
       # Note that post_config isnt used for this case
       [fun.(get)]
     end
   end
 
+  defp extract_projects(paths) do
+    lc path inlist paths do
+      app = path |> Path.basename |> String.downcase |> binary_to_atom
+      { app, path }
+    end
+  end
+
+  defp filter_projects(pairs, nil), do: pairs
+  defp filter_projects(pairs, apps) when is_list(apps) do
+    lc { app, _ } = pair inlist pairs, app in apps, do: pair
+  end
+
+  defp recur_projects(pairs, post_config, fun) do
+    lc { app, path } inlist pairs do
+      in_project(app, path, post_config, fun)
+    end
+  end
+
   @doc """
   Runs the given `fun` inside the given project by changing
   the current working directory and loading the given project

lib/mix/test/mix/tasks/compile.elixir_test.exs

@@ -96,22 +96,6 @@ defmodule Mix.Tasks.Compile.ElixirTest do
     end
   end
 
-  test "recompiles after path dependency changed" do
-    in_fixture("umbrella_dep/deps/umbrella/apps", fn ->
-      Mix.Project.in_project(:bar, "bar", fn _ ->
-        Mix.Tasks.Deps.Compile.run []
-
-        assert Mix.Tasks.Compile.Elixir.run([]) == :ok
-        assert Mix.Tasks.Compile.Elixir.run([]) == :noop
-        purge [Bar]
-
-        future = { { 2020, 4, 17 }, { 14, 0, 0 } }
-        File.touch!("../foo/ebin/.compile.elixir", future)
-        assert Mix.Tasks.Compile.Elixir.run([]) == :ok
-      end)
-    end)
-  end
-
   test "recompiles with --force" do
     in_fixture "no_mixfile", fn ->
       assert Mix.Tasks.Compile.Elixir.run([]) == :ok

lib/mix/test/mix/umbrella_test.exs

@@ -51,4 +51,42 @@ defmodule Mix.UmbrellaTest do
       end)
     end
   end
+
+  test "recompiles after path dependency changed" do
+    in_fixture("umbrella_dep/deps/umbrella/apps", fn ->
+      Mix.Project.in_project(:bar, "bar", fn _ ->
+        Mix.Tasks.Deps.Compile.run []
+
+        assert Mix.Tasks.Compile.Elixir.run([]) == :ok
+        assert Mix.Tasks.Compile.Elixir.run([]) == :noop
+        purge [Bar]
+
+        future = { { 2020, 4, 17 }, { 14, 0, 0 } }
+        File.touch!("../foo/ebin/.compile.elixir", future)
+        assert Mix.Tasks.Compile.Elixir.run([]) == :ok
+      end)
+    end)
+  end
+
+  defmodule Selective.Mixfile do
+    def project do
+      [ apps_path: "apps",
+        apps: [:foo, :bar] ]
+    end
+  end
+
+  test "can select which apps to use" do
+    in_fixture("umbrella_dep/deps/umbrella", fn ->
+      Mix.Project.push Selective.Mixfile
+
+      File.mkdir_p! "apps/errors/lib"
+      File.write! "apps/errors/lib/always_fail.ex", "raise %s[oops]"
+
+      assert Mix.Task.run("compile.elixir") == [:ok, :ok]
+      assert_received { :mix_shell, :info, ["Compiled lib/bar.ex"] }
+      assert_received { :mix_shell, :info, ["Compiled lib/foo.ex"] }
+    end)
+  after
+    Mix.Project.pop
+  end
 end