From 372ef9b32053c82f15bf84608497702638deb786 Mon Sep 17 00:00:00 2001
From: Lukasz Samson <lukaszsamson@gmail.com>
Date: Thu, 28 Sep 2023 22:02:38 +0200
Subject: [PATCH] Apply upstream fix for
 https://github.com/elixir-lang/elixir/issues/12969

Fixes https://github.com/elixir-lsp/elixir-ls/issues/992
---
 .../lib/language_server/mix_tasks/format.ex           | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/apps/language_server/lib/language_server/mix_tasks/format.ex b/apps/language_server/lib/language_server/mix_tasks/format.ex
index c7c45bfe5..00df7656d 100644
--- a/apps/language_server/lib/language_server/mix_tasks/format.ex
+++ b/apps/language_server/lib/language_server/mix_tasks/format.ex
@@ -608,8 +608,15 @@ defmodule Mix.Tasks.ElixirLSFormat do
 
   defp recur_formatter_opts_for_file(file, {formatter_opts, subs}) do
     Enum.find_value(subs, formatter_opts, fn {sub, formatter_opts_and_subs} ->
-      if String.starts_with?(file, sub) do
-        recur_formatter_opts_for_file(file, 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)
+
+        _ ->
+          nil
       end
     end)
   end