Add support for mix format plugins (#660)

apps/language_server/lib/language_server/providers/execute_command/apply_spec.ex

@@ -56,8 +56,8 @@ defmodule ElixirLS.LanguageServer.Providers.ExecuteCommand.ApplySpec do
     formatted =
       try do
         target_line_length =
-          case SourceFile.formatter_opts(uri) do
-            {:ok, opts} -> Keyword.get(opts, :line_length, @default_target_line_length)
+          case SourceFile.formatter_for(uri) do
+            {:ok, {_, opts}} -> Keyword.get(opts, :line_length, @default_target_line_length)
             :error -> @default_target_line_length
           end
 
@@ -94,3 +94,4 @@ defmodule ElixirLS.LanguageServer.Providers.ExecuteCommand.ApplySpec do
     end
   end
 end
+

apps/language_server/lib/language_server/providers/formatting.ex

@@ -5,7 +5,14 @@ defmodule ElixirLS.LanguageServer.Providers.Formatting do
 
   def format(%SourceFile{} = source_file, uri, project_dir) when is_binary(project_dir) do
     if can_format?(uri, project_dir) do
-      case SourceFile.formatter_opts(uri) do
+      case SourceFile.formatter_for(uri) do
+        {:ok, {formatter, opts}} ->
+          if should_format?(uri, project_dir, opts[:inputs]) do
+            do_format(source_file, formatter, opts)
+          else
+            {:ok, []}
+          end
+
         {:ok, opts} ->
           if should_format?(uri, project_dir, opts[:inputs]) do
             do_format(source_file, opts)
@@ -29,8 +36,11 @@ defmodule ElixirLS.LanguageServer.Providers.Formatting do
     do_format(source_file)
   end
 
-  defp do_format(%SourceFile{text: text}, opts \\ []) do
-    formatted = IO.iodata_to_binary([Code.format_string!(text, opts), ?\n])
+
+  defp do_format(%SourceFile{} = source_file, opts \\ []), do: do_format(source_file, nil, opts)
+
+  defp do_format(%SourceFile{text: text}, formatter, opts) do
+    formatted = get_formatted(text, formatter, opts)
 
     response =
       text
@@ -43,6 +53,14 @@ defmodule ElixirLS.LanguageServer.Providers.Formatting do
       {:error, :internal_error, "Unable to format due to syntax error"}
   end
 
+  defp get_formatted(text, formatter, _) when is_function(formatter) do
+    formatter.(text)
+  end
+
+  defp get_formatted(text, _, opts) do
+    IO.iodata_to_binary([Code.format_string!(text, opts), ?\n])
+  end
+
   # If in an umbrella project, the cwd might be set to a sub-app if it's being compiled. This is
   # fine if the file we're trying to format is in that app. Otherwise, we return an error.
   defp can_format?(file_uri = "file:" <> _, project_dir) do

apps/language_server/lib/language_server/server.ex

@@ -670,8 +670,8 @@ defmodule ElixirLS.LanguageServer.Server do
       !!get_in(state.client_capabilities, ["textDocument", "signatureHelp"])
 
     locals_without_parens =
-      case SourceFile.formatter_opts(uri) do
-        {:ok, opts} -> Keyword.get(opts, :locals_without_parens, [])
+      case SourceFile.formatter_for(uri) do
+        {:ok, {_, opts}} -> Keyword.get(opts, :locals_without_parens, [])
         :error -> []
       end
       |> MapSet.new()
@@ -1258,3 +1258,4 @@ defmodule ElixirLS.LanguageServer.Server do
     end)
   end
 end
+

apps/language_server/lib/language_server/source_file.ex

@@ -334,16 +334,16 @@ defmodule ElixirLS.LanguageServer.SourceFile do
     """
   end
 
-  @spec formatter_opts(String.t()) :: {:ok, keyword()} | :error
-  def formatter_opts(uri = "file:" <> _) do
+  @spec formatter_for(String.t()) :: {:ok, keyword()} | :error
+  def formatter_for(uri = "file:" <> _) do
     path = path_from_uri(uri)
 
     try do
-      opts =
-        path
-        |> Mix.Tasks.Format.formatter_opts_for_file()
-
-      {:ok, opts}
+      if function_exported?(Mix.Tasks.Format, :formatter_for_file, 1) do
+        {:ok, Mix.Tasks.Format.formatter_for_file(path)}
+      else
+        {:ok, {nil, Mix.Tasks.Format.formatter_opts_for_file(path)}}
+      end
     rescue
       e ->
         IO.warn(
@@ -354,7 +354,7 @@ defmodule ElixirLS.LanguageServer.SourceFile do
     end
   end
 
-  def formatter_opts(_), do: :error
+  def formatter_for(_), do: :error
 
   defp format_code(code, opts) do
     try do
@@ -431,3 +431,4 @@ defmodule ElixirLS.LanguageServer.SourceFile do
     {elixir_line - 1, utf16_character}
   end
 end
+