Change directory permissions after writing, closes #15286

Author: josevalim

lib/elixir/lib/file.ex

@@ -1293,23 +1293,30 @@ defmodule File do
           {:ok, files} ->
             case mkdir(dest) do
               success when success in [:ok, {:error, :eexist}] ->
-                case copy_file_mode(src, dest) do
-                  :ok ->
-                    Enum.reduce_while(files, [dest | acc], fn x, acc ->
-                      case do_cp_r(
-                             Path.join(src, x),
-                             Path.join(dest, x),
-                             on_conflict,
-                             dereference,
-                             acc
-                           ) do
-                        {:error, _, _} = error -> {:halt, error}
-                        acc -> {:cont, acc}
-                      end
-                    end)
-
-                  {:error, reason} ->
-                    {:error, reason, src}
+                files
+                |> Enum.reduce_while([dest | acc], fn x, acc ->
+                  case do_cp_r(
+                         Path.join(src, x),
+                         Path.join(dest, x),
+                         on_conflict,
+                         dereference,
+                         acc
+                       ) do
+                    {:error, _, _} = error -> {:halt, error}
+                    acc -> {:cont, acc}
+                  end
+                end)
+                |> case do
+                  {:error, _, _} = error ->
+                    error
+
+                  files ->
+                    # Change the directory after writing files in case
+                    # it was originally read only
+                    case copy_file_mode(src, dest) do
+                      :ok -> files
+                      {:error, reason} -> {:error, reason, src}
+                    end
                 end
 
               {:error, reason} ->

lib/elixir/test/elixir/file_test.exs

@@ -875,15 +875,20 @@ defmodule FileTest do
       inner = Path.join(src, "inner")
 
       File.mkdir_p!(inner)
-      File.chmod!(inner, 0o700)
+      File.write!(Path.join(inner, "hello"), "world")
+      File.chmod!(inner, 0o500)
 
       try do
         File.cp_r!(src, dest)
 
         %File.Stat{mode: src_mode} = File.stat!(inner)
         %File.Stat{mode: dest_mode} = File.stat!(Path.join(dest, "inner"))
         assert src_mode == dest_mode
+
+        assert File.read!(Path.join(dest, "inner/hello")) == "world"
       after
+        File.chmod!(inner, 0o700)
+        File.chmod!(Path.join(dest, "inner"), 0o700)
         File.rm_rf!(src)
         File.rm_rf!(dest)
       end