Always rebuild structures on Windows

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

Author: José Valim

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

@@ -52,6 +52,19 @@ defmodule Mix.Compilers.Elixir do
       removed != [] ->
         write_manifest(manifest, entries ++ skip_entries)
         :ok
+      File.exists?(Mix.Project.app_path) ->
+        # If we have an app path but a noop result, we rebuild
+        # the structure because priv/include needs to be recopied when
+        # symlink is not available. We do this in the Elixir compiler
+        # instead of the main compiler one because other compilers may
+        # return :ok, saying they did some work, but they may have not
+        # built a structure at all.
+        #
+        # This implies the Elixir compiler is somewhat required, even
+        # for Erlang projects, which is an ok assumption to make (we
+        # ship with both Elixir and Erlang compilers by default).
+        Mix.Project.build_structure()
+        :noop
       true ->
         :noop
     end

lib/mix/lib/mix/tasks/compile.app.ex

@@ -99,7 +99,9 @@ defmodule Mix.Tasks.Compile.App do
       properties = ensure_correct_properties(app, config, properties)
       contents   = {:application, app, properties}
 
-      Mix.Project.build_structure(config)
+      # There are no modules, we assume no structure was built.
+      # If it was built, it doesn't matter, we just rebuild it.
+      if mods == [], do: Mix.Project.build_structure(config)
       File.write!(target, :io_lib.format("~p.", [contents]))
 
       Mix.shell.info "Generated #{app}.app"

lib/mix/lib/mix/tasks/deps.compile.ex

@@ -64,10 +64,7 @@ defmodule Mix.Tasks.Deps.Compile do
               "(pass :compile as an option to customize compilation, set it to false to do nothing)"
         end
 
-        # Always build the structure even for Mix projects
-        # because if nothing was compiled, we need to re-copy
-        # priv/include when symlinks are not available.
-        build_structure(dep, config)
+        unless mix?(dep), do: build_structure(dep, config)
         touch_fetchable(scm, opts[:build])
         compiled
       end)