Traverse dependnecies when consolidate umbrella protocols, closes #4842

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: José Valim

lib/mix/lib/mix/tasks/compile.protocols.ex

@@ -44,10 +44,7 @@ defmodule Mix.Tasks.Compile.Protocols do
     output   = Mix.Project.consolidation_path(config)
     manifest = Path.join(output, @manifest)
 
-    protocols_and_impls =
-      unless Mix.Project.umbrella?(config) do
-        protocols_and_impls(config)
-      end
+    protocols_and_impls = protocols_and_impls(config)
 
     cond do
       opts[:force] || Mix.Utils.stale?(Mix.Project.config_files(), [manifest]) ->
@@ -79,10 +76,15 @@ defmodule Mix.Tasks.Compile.Protocols do
                not scm.fetchable?,
                do: opts[:build])
 
-    app = Mix.Project.app_path(config)
+    app =
+      if Mix.Project.umbrella?(config) do
+        []
+      else
+        [Mix.Project.app_path(config)]
+      end
 
     protocols_and_impls =
-      for path <- [app | deps] do
+      for path <- app ++ deps do
         manifest_path = Path.join(path, ".compile.elixir")
         compile_path = Path.join(path, "ebin")
         Mix.Compilers.Elixir.protocols_and_impls(manifest_path, compile_path)

lib/mix/test/mix/umbrella_test.exs

@@ -364,6 +364,30 @@ defmodule Mix.UmbrellaTest do
     end)
   end
 
+  test "reconsolidates using umbrella information even on shared _build" do
+    in_fixture("umbrella_dep/deps/umbrella", fn ->
+      File.write!("apps/bar/lib/bar.ex", """
+      defprotocol Bar do
+        def bar(arg)
+      end
+      defimpl Bar, for: List do
+        def bar(list), do: list
+      end
+      """)
+
+      Mix.Project.in_project(:foo, "apps/foo", [build_path: "../../_build"], fn _ ->
+        Mix.Task.run("compile.protocols")
+        refute Code.ensure_loaded?(Bar)
+      end)
+
+      Mix.Project.in_project(:umbrella, ".", fn _ ->
+        Mix.Task.run("compile.protocols")
+        Mix.Task.run("app.start")
+        assert Protocol.consolidated?(Bar)
+      end)
+    end)
+  end
+
   defmodule Selective do
     def project do
       [apps_path: "apps",