Add preferred_cli_target (#9118)

Author: mobileoverlord

lib/mix/lib/mix/cli.ex

@@ -29,7 +29,7 @@ defmodule Mix.CLI do
     load_mix_exs()
     {task, args} = get_task(args)
     ensure_hex(task)
-    change_env(task)
+    maybe_change_env_and_target(task)
     run_task(task, args)
   end
 
@@ -104,26 +104,39 @@ defmodule Mix.CLI do
     end
   end
 
-  defp change_env(task) do
-    if env = preferred_cli_env(task) do
-      Mix.env(env)
+  defp maybe_change_env_and_target(task) do
+    task = String.to_atom(task)
+    config = Mix.Project.config()
 
-      if project = Mix.Project.pop() do
-        %{name: name, file: file} = project
-        Mix.Project.push(name, file)
-      end
+    env = preferred_cli_env(task, config)
+    target = preferred_cli_target(task, config)
+    env && Mix.env(env)
+    target && Mix.target(target)
+
+    if env || target do
+      reload_project()
+    end
+  end
+
+  defp reload_project() do
+    if project = Mix.Project.pop() do
+      %{name: name, file: file} = project
+      Mix.Project.push(name, file)
     end
   end
 
-  defp preferred_cli_env(task) do
+  defp preferred_cli_env(task, config) do
     if System.get_env("MIX_ENV") do
       nil
     else
-      task = String.to_atom(task)
-      Mix.Project.config()[:preferred_cli_env][task] || Mix.Task.preferred_cli_env(task)
+      config[:preferred_cli_env][task] || Mix.Task.preferred_cli_env(task)
     end
   end
 
+  defp preferred_cli_target(task, config) do
+    config[:preferred_cli_target][task]
+  end
+
   defp load_dot_config do
     path = Path.join(Mix.Utils.mix_config(), "config.exs")
 

lib/mix/lib/mix/project.ex

@@ -67,9 +67,13 @@ defmodule Mix.Project do
     * `:preferred_cli_env` - a keyword list of `{task, env}` tuples where `task`
       is the task name as an atom (for example, `:"deps.get"`) and `env` is the
       preferred environment (for example, `:test`). This option overrides what
-      specified by the tasks with the `@preferred_cli_env` attribute (see the
+      is specified by the tasks with the `@preferred_cli_env` attribute (see the
       docs for `Mix.Task`). Defaults to `[]`.
 
+    * `:preferred_cli_target` - a keyword list of `{task, target}` tuples where
+      `task` is the task name as an atom (for example, `:test`) and `target`
+      is the preferred target (for example, `:host`). Defaults to `[]`.
+
   For more options, keep an eye on the documentation for single Mix tasks; good
   examples are the `Mix.Tasks.Compile` task and all the specific compiler tasks
   (such as `Mix.Tasks.Compile.Elixir` or `Mix.Tasks.Compile.Erlang`).

lib/mix/test/mix/cli_test.exs

@@ -143,6 +143,32 @@ defmodule Mix.CLITest do
     System.delete_env("MIX_EXS")
   end
 
+  test "target config defaults to the user's preferred cli target", context do
+    in_tmp(context.test, fn ->
+      File.write!("custom.exs", """
+      defmodule P do
+        use Mix.Project
+        def project, do: [app: :p, version: "0.1.0", preferred_cli_target: [test_task: :other]]
+      end
+
+      defmodule Mix.Tasks.TestTask do
+        use Mix.Task
+
+        def run(args) do
+          IO.inspect {Mix.target, args}
+        end
+      end
+      """)
+
+      System.put_env("MIX_EXS", "custom.exs")
+
+      output = mix(["test_task", "a", "b", "c"])
+      assert output =~ ~s({:other, ["a", "b", "c"]})
+    end)
+  after
+    System.delete_env("MIX_EXS")
+  end
+
   test "new with tests and cover" do
     in_tmp("new_with_tests", fn ->
       output = mix(~w[new .])