Do not crash if unable to get formatter options (#319)

Fixes #318

Author: lukaszsamson

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

@@ -6,6 +6,8 @@ defmodule ElixirLS.LanguageServer.Providers.ExecuteCommand do
   alias ElixirLS.LanguageServer.{JsonRpc, SourceFile}
   import ElixirLS.LanguageServer.Protocol
 
+  @default_target_line_length 98
+
   def execute("spec:" <> _, args, source_files) do
     [
       %{
@@ -47,9 +49,10 @@ defmodule ElixirLS.LanguageServer.Providers.ExecuteCommand do
     formatted =
       try do
         target_line_length =
-          uri
-          |> SourceFile.formatter_opts()
-          |> Keyword.get(:line_length, 98)
+          case SourceFile.formatter_opts(uri) do
+            {:ok, opts} -> Keyword.get(opts, :line_length, @default_target_line_length)
+            :error -> @default_target_line_length
+          end
 
         target_line_length = target_line_length - String.length(indentation)
 

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

@@ -8,19 +8,23 @@ defmodule ElixirLS.LanguageServer.Providers.Formatting do
 
   def format(source_file, uri, project_dir) do
     if can_format?(uri, project_dir) do
-      opts = SourceFile.formatter_opts(uri)
-
-      if should_format?(uri, project_dir, opts[:inputs]) do
-        formatted = IO.iodata_to_binary([Code.format_string!(source_file.text, opts), ?\n])
-
-        response =
-          source_file.text
-          |> String.myers_difference(formatted)
-          |> myers_diff_to_text_edits()
-
-        {:ok, response}
-      else
-        {:ok, []}
+      case SourceFile.formatter_opts(uri) do
+        {:ok, opts} ->
+          if should_format?(uri, project_dir, opts[:inputs]) do
+            formatted = IO.iodata_to_binary([Code.format_string!(source_file.text, opts), ?\n])
+
+            response =
+              source_file.text
+              |> String.myers_difference(formatted)
+              |> myers_diff_to_text_edits()
+
+            {:ok, response}
+          else
+            {:ok, []}
+          end
+
+        :error ->
+          {:error, :internal_error, "Unable to fetch formatter options"}
       end
     else
       msg =

apps/language_server/lib/language_server/server.ex

@@ -483,9 +483,10 @@ defmodule ElixirLS.LanguageServer.Server do
       !!get_in(state.client_capabilities, ["textDocument", "signatureHelp"])
 
     locals_without_parens =
-      uri
-      |> SourceFile.formatter_opts()
-      |> Keyword.get(:locals_without_parens, [])
+      case SourceFile.formatter_opts(uri) do
+        {:ok, opts} -> Keyword.get(opts, :locals_without_parens, [])
+        :error -> []
+      end
       |> MapSet.new()
 
     fun = fn ->

apps/language_server/lib/language_server/source_file.ex

@@ -211,11 +211,21 @@ defmodule ElixirLS.LanguageServer.SourceFile do
     """
   end
 
-  @spec formatter_opts(String.t()) :: keyword()
+  @spec formatter_opts(String.t()) :: {:ok, keyword()} | :error
   def formatter_opts(uri) do
-    uri
-    |> path_from_uri()
-    |> Mix.Tasks.Format.formatter_opts_for_file()
+    path = path_from_uri(uri)
+
+    try do
+      opts =
+        path
+        |> Mix.Tasks.Format.formatter_opts_for_file()
+
+      {:ok, opts}
+    rescue
+      e in Mix.Error ->
+        IO.warn("Unable to get formatter options for #{path}: #{e.message}")
+        :error
+    end
   end
 
   defp format_code(code, opts) do