Attach :root to returned formatter options

Author: josevalim

lib/mix/lib/mix/tasks/format.ex

@@ -357,8 +357,12 @@ defmodule Mix.Tasks.Format do
   be used for the given file.
 
   The function must be called with the contents of the file
-  to be formatted. The options are returned for reflection
-  purposes.
+  to be formatted. Keep in mind that a function is always
+  returned, even if it doesn't match any of the inputs
+  specified in the `formatter.exs`. You can retrieve the
+  `:inputs` from the returned options, alongside the `:root`
+  option, to validate if the returned file matches the given
+  `:root` and `:inputs`.
 
   ## Options
 
@@ -390,7 +394,7 @@ defmodule Mix.Tasks.Format do
 
     formatter_opts_and_subs = load_plugins(formatter_opts_and_subs, opts)
 
-    find_formatter_and_opts_for_file(Path.expand(file, cwd), formatter_opts_and_subs)
+    find_formatter_and_opts_for_file(Path.expand(file, cwd), cwd, formatter_opts_and_subs)
   end
 
   @doc false
@@ -589,11 +593,11 @@ defmodule Mix.Tasks.Format do
         stdin_filename = Path.expand(Keyword.get(opts, :stdin_filename, "stdin.exs"), cwd)
 
         {formatter, _opts} =
-          find_formatter_and_opts_for_file(stdin_filename, {formatter_opts, subs})
+          find_formatter_and_opts_for_file(stdin_filename, cwd, {formatter_opts, subs})
 
         {file, formatter}
       else
-        {formatter, _opts} = find_formatter_and_opts_for_file(file, {formatter_opts, subs})
+        {formatter, _opts} = find_formatter_and_opts_for_file(file, cwd, {formatter_opts, subs})
         {file, formatter}
       end
     end
@@ -659,19 +663,19 @@ defmodule Mix.Tasks.Format do
     if plugins != [], do: plugins, else: nil
   end
 
-  defp find_formatter_and_opts_for_file(file, formatter_opts_and_subs) do
-    formatter_opts = recur_formatter_opts_for_file(file, formatter_opts_and_subs)
-    {find_formatter_for_file(file, formatter_opts), formatter_opts}
+  defp find_formatter_and_opts_for_file(file, root, formatter_opts_and_subs) do
+    {formatter_opts, root} = recur_formatter_opts_for_file(file, root, formatter_opts_and_subs)
+    {find_formatter_for_file(file, formatter_opts), [root: root] ++ formatter_opts}
   end
 
-  defp recur_formatter_opts_for_file(file, {formatter_opts, subs}) do
-    Enum.find_value(subs, formatter_opts, fn {sub, formatter_opts_and_subs} ->
+  defp recur_formatter_opts_for_file(file, root, {formatter_opts, subs}) do
+    Enum.find_value(subs, {formatter_opts, root}, fn {sub, formatter_opts_and_subs} ->
       size = byte_size(sub)
 
       case file do
         <<prefix::binary-size(size), dir_separator, _::binary>>
         when prefix == sub and dir_separator in [?\\, ?/] ->
-          recur_formatter_opts_for_file(file, formatter_opts_and_subs)
+          recur_formatter_opts_for_file(file, sub, formatter_opts_and_subs)
 
         _ ->
           nil

lib/mix/test/mix/tasks/format_test.exs

@@ -608,7 +608,7 @@ defmodule Mix.Tasks.FormatTest do
 
       root = File.cwd!()
 
-      {formatter_function, _options} =
+      {formatter_function, options} =
         File.cd!("lib", fn ->
           Mix.Tasks.Format.formatter_for_file("lib/a.ex", root: root)
         end)
@@ -618,6 +618,8 @@ defmodule Mix.Tasks.FormatTest do
              """) == """
              foo bar(baz)
              """
+
+      assert options[:root] == root
     end)
   end
 
@@ -642,12 +644,14 @@ defmodule Mix.Tasks.FormatTest do
 
       # Should hit the formatter
       {formatter, formatter_opts} = Mix.Tasks.Format.formatter_for_file("lib/extra/a.ex")
-      assert Keyword.get(formatter_opts, :locals_without_parens) == [my_fun: 2]
+      assert formatter_opts[:root] == Path.expand("lib")
+      assert formatter_opts[:locals_without_parens] == [my_fun: 2]
       assert formatter.("my_fun 1, 2") == "my_fun 1, 2\n"
 
       # Another directory should not hit the formatter
       {formatter, formatter_opts} = Mix.Tasks.Format.formatter_for_file("test/a.ex")
-      assert Keyword.get(formatter_opts, :locals_without_parens) == []
+      assert formatter_opts[:root] == Path.expand(".")
+      assert formatter_opts[:locals_without_parens] == []
       assert formatter.("my_fun 1, 2") == "my_fun(1, 2)\n"
 
       File.write!("lib/a.ex", """
@@ -718,7 +722,7 @@ defmodule Mix.Tasks.FormatTest do
       File.touch!(manifest_path, {{2010, 1, 1}, {0, 0, 0}})
 
       {_, formatter_opts} = Mix.Tasks.Format.formatter_for_file("a.ex")
-      assert [my_fun: 2] = Keyword.get(formatter_opts, :locals_without_parens)
+      assert [my_fun: 2] = formatter_opts[:locals_without_parens]
 
       # Check the deps_path option is respected
       assert_raise Mix.Error, ~r"Unknown dependency :my_dep given to :import_deps", fn ->
@@ -810,7 +814,8 @@ defmodule Mix.Tasks.FormatTest do
       Mix.Tasks.Format.run([])
 
       {_, formatter_opts} = Mix.Tasks.Format.formatter_for_file("lib/extra/a.ex")
-      assert [other_fun: 1] = Keyword.get(formatter_opts, :locals_without_parens)
+      assert formatter_opts[:root] == Path.expand("lib/extra")
+      assert formatter_opts[:locals_without_parens] == [other_fun: 1]
 
       assert File.read!("lib/extra/a.ex") == """
              my_fun(:foo, :bar)