Avoid missing behaviour warnings when compiling erlang files

Author: José Valim

lib/mix/lib/mix/compilers/elixir.ex

@@ -99,6 +99,8 @@ defmodule Mix.Compilers.Elixir do
 
   defp compile_manifest(manifest, entries, stale, dest, on_start) do
     Mix.Project.build_structure
+    true = Code.prepend_path(dest)
+
     on_start.()
     cwd = File.cwd!
 

lib/mix/lib/mix/compilers/erlang.ex

@@ -72,6 +72,11 @@ defmodule Mix.Compilers.Erlang do
       # Build the project structure so we can write down compiled files.
       Mix.Project.build_structure
 
+      # Let's prepend the newly created path so compiled files
+      # can be accessed still during compilation (for behaviours
+      # and what not).
+      Code.prepend_path(Mix.Project.compile_path)
+
       # Remove manifest entries with no source
       Enum.each(removed, &File.rm/1)
 

lib/mix/lib/mix/tasks/compile.elixir.ex

@@ -65,7 +65,6 @@ defmodule Mix.Tasks.Compile.Elixir do
               || Mix.Utils.stale?(configs, [manifest])
 
     Mix.Compilers.Elixir.compile(manifest, srcs, skip, [:ex], dest, force, fn ->
-      true = Code.prepend_path(dest)
       set_compiler_opts(project, opts, [])
     end)
   end

lib/mix/lib/mix/tasks/compile.erlang.ex

@@ -167,6 +167,6 @@ defmodule Mix.Tasks.Compile.Erlang do
   end
 
   defp module_from_artifact(artifact) do
-    artifact |> Path.basename |> Path.rootname
+    artifact |> Path.basename |> Path.rootname |> String.to_atom
   end
 end

lib/mix/lib/mix/tasks/deps.check.ex

@@ -84,7 +84,7 @@ defmodule Mix.Tasks.Deps.Check do
       to_prune = Enum.reduce(all, paths, &(&2 -- Mix.Dep.load_paths(&1)))
 
       Enum.map(to_prune, fn path ->
-        # Path may not be in code path
+        # Path cannot be in code path when deleting
         _ = Code.delete_path(path)
         File.rm_rf!(path |> Path.dirname)
       end)

lib/mix/test/fixtures/compile_erlang/src/b.erl

@@ -1,6 +1,7 @@
 -module(b).
 -compile(export_all).
 
+-callback c() -> term().
 -record(br, {cell=undefined}).
 
-b() -> #br{cell=specified}.
+b() -> #br{cell=specified}.

lib/mix/test/fixtures/compile_erlang/src/c.erl

@@ -2,5 +2,6 @@
 -compile(export_all).
 
 -include("r.hrl").
+-behaviour(b).
 
 c() -> #r{cell=specified}.