Allow mix loadconfig to be called multiple times

Author: José Valim

lib/mix/lib/mix/cli.ex

@@ -113,9 +113,7 @@ defmodule Mix.CLI do
   defp load_dot_config do
     path = Path.expand("~/.mix/config.exs")
     if File.regular?(path) do
-      path
-      |> Mix.Config.read!()
-      |> Mix.Config.persist()
+      Mix.Task.run "loadconfig", [path]
     end
   end
 

lib/mix/lib/mix/tasks/loadconfig.ex

@@ -1,13 +1,32 @@
 defmodule Mix.Tasks.Loadconfig do
   use Mix.Task
 
+  @shortdoc "Loads and persists the given configuration"
+
   @moduledoc """
-  Loads and persists the project configuration.
-  """
+  Loads and persists the given configuration.
 
-  def run(_) do
-    if File.regular?("config/config.exs") do
-      Mix.Config.persist Mix.Config.read! "config/config.exs"
+  In case no configuration file is given, it
+  loads the project oe at "config/config.exs".
+
+  This task is automatically reenabled, so it
+  can be called multiple times to load different
+  configs.
+  """
+  def run(args) do
+    cond do
+      file = Enum.at(args, 0) ->
+        load file
+      File.regular?("config/config.exs") ->
+        load "config/config.exs"
+      true ->
+        :ok
     end
+
+    Mix.Task.reenable "loadconfig"
+  end
+
+  defp load(file) do
+    Mix.Config.persist Mix.Config.read! file
   end
 end

lib/mix/test/mix/tasks/loadconfig_test.exs

@@ -16,18 +16,25 @@ defmodule Mix.Tasks.LoadconfigTest do
     :ok
   end
 
-  test "reads and persists application configuration" do
+  test "reads and persists project configuration" do
     Mix.Project.push MixTest.Case.Sample
 
     in_fixture "no_mixfile", fn ->
       write_config """
-      [my_app: [key: :value]]
+      [my_app: [key: :project]]
       """
 
       assert Application.fetch_env(:my_app, :key) == :error
-      Mix.Tasks.Loadconfig.run []
-      assert Application.fetch_env(:my_app, :key) == {:ok, :value}
+      Mix.Task.run "loadconfig", []
+      assert Application.fetch_env(:my_app, :key) == {:ok, :project}
+
+      # App configuration should have lower precedence
       :ok = :application.load({:application, :my_app, [vsn: '1.0.0', env: [key: :app]]})
+      assert Application.fetch_env(:my_app, :key) == {:ok, :project}
+
+      # laodconfig can be called multiple times
+      # Later values should have higher precedence
+      Mix.Task.run "loadconfig", [fixture_path("configs/good_config.exs")]
       assert Application.fetch_env(:my_app, :key) == {:ok, :value}
     end
   end