Support proper encoding in releases config

lib/elixir/lib/config/provider.ex

@@ -350,7 +350,7 @@ defmodule Config.Provider do
   defp write_config!(config, path) do
     contents = :io_lib.format("%% coding: utf-8~n~tw.~n", [config])
 
-    case File.write(path, contents, [:utf8]) do
+    case File.write(path, IO.chardata_to_string(contents)) do
       :ok ->
         :ok
 

lib/elixir/test/elixir/config/provider_test.exs

@@ -83,11 +83,11 @@ defmodule Config.ProviderTest do
       assert config[@config_app] == [config_providers_booted: {:booted, nil}]
     end
 
-    @tag sys_config: [my_app: [encoding: {:"£", "£", '£'}]]
+    @tag sys_config: [my_app: [encoding: {:time_μs, :"£", "£", '£'}]]
     test "writes sys_config with encoding" do
       init_and_assert_boot()
       config = consult(@sys_config)
-      assert config[:my_app][:encoding] == {:"£", "£", '£'}
+      assert config[:my_app][:encoding] == {:time_μs, :"£", "£", '£'}
     end
 
     @tag sys_config: [my_app: [key: :old_value, sys_key: :sys_value, extra_config: :old_value]]
@@ -185,6 +185,6 @@ defmodule Config.ProviderTest do
   end
 
   defp write_sys_config!(data) do
-    File.write!(@sys_config, :io_lib.format("~tw.~n", [data]), [:utf8])
+    File.write!(@sys_config, IO.chardata_to_string(:io_lib.format("~tw.~n", [data])))
   end
 end

lib/mix/lib/mix/release.ex

@@ -403,7 +403,7 @@ defmodule Mix.Release do
     args = [runtime_config?, sys_config]
     format = "%% coding: utf-8~n%% RUNTIME_CONFIG=~s~n~tw.~n"
     File.mkdir_p!(Path.dirname(path))
-    File.write!(path, :io_lib.format(format, args), [:utf8])
+    File.write!(path, IO.chardata_to_string(:io_lib.format(format, args)))
 
     case :file.consult(path) do
       {:ok, _} ->
@@ -513,7 +513,7 @@ defmodule Mix.Release do
           :ok | {:error, String.t()}
   def make_boot_script(release, path, modes, prepend_paths \\ []) do
     with {:ok, rel_spec} <- build_release_spec(release, modes) do
-      File.write!(path <> ".rel", consultable(rel_spec), [:utf8])
+      File.write!(path <> ".rel", consultable(rel_spec))
 
       sys_path = String.to_charlist(path)
 
@@ -536,7 +536,7 @@ defmodule Mix.Release do
             |> prepend_paths_to_script(prepend_paths)
 
           script = {:script, rel_info, instructions}
-          File.write!(script_path, consultable(script), [:utf8])
+          File.write!(script_path, consultable(script))
           :ok = :systools.script2boot(sys_path)
 
         {:error, module, info} ->
@@ -658,7 +658,7 @@ defmodule Mix.Release do
   end
 
   defp consultable(term) do
-    :io_lib.format("%% coding: utf-8~n~tp.~n", [term])
+    IO.chardata_to_string(:io_lib.format("%% coding: utf-8~n~tp.~n", [term]))
   end
 
   @doc """

lib/mix/test/fixtures/release_test/config/config.exs

@@ -1,4 +1,4 @@
 import Config
 
 config :release_test, :static, :was_set
-config :release_test, :encoding, {:"£", "£", '£'}
+config :release_test, :encoding, {:time_μs, :"£", "£", '£'}

lib/mix/test/mix/release_test.exs

@@ -488,11 +488,15 @@ defmodule Mix.ReleaseTest do
     end
 
     test "writes sys_config with encoding" do
-      assert make_sys_config(release([]), [encoding: {:"£", "£", '£'}], "unused/runtime/path") ==
+      assert make_sys_config(
+               release([]),
+               [encoding: {:time_μs, :"£", "£", '£'}],
+               "unused/runtime/path"
+             ) ==
                :ok
 
       {:ok, contents} = :file.consult(@sys_config)
-      assert contents == [[encoding: {:"£", "£", '£'}]]
+      assert contents == [[encoding: {:time_μs, :"£", "£", '£'}]]
     end
 
     test "writes the given sys_config with config providers" do

lib/mix/test/mix/tasks/release_test.exs

@@ -281,7 +281,7 @@ defmodule Mix.Tasks.ReleaseTest do
         assert %{
                  app_dir: app_dir,
                  cookie_env: ^cookie,
-                 encoding: {:"£", "£", '£'},
+                 encoding: {:time_μs, :"£", "£", '£'},
                  mode: :embedded,
                  node: release_node("release_test"),
                  protocols_consolidated?: true,
@@ -322,7 +322,7 @@ defmodule Mix.Tasks.ReleaseTest do
         File.write!("config/releases.exs", """
         import Config
         config :release_test, :runtime, :was_set
-        config :release_test, :encoding, {:runtime, :"£", "£", '£'}
+        config :release_test, :encoding, {:runtime, :time_μs, :"£", "£", '£'}
         """)
 
         root = Path.absname("_build/dev/rel/runtime_config")
@@ -348,7 +348,7 @@ defmodule Mix.Tasks.ReleaseTest do
         open_port(Path.join(root, "bin/runtime_config"), ['start'])
 
         assert %{
-                 encoding: {:runtime, :"£", "£", '£'},
+                 encoding: {:runtime, :time_μs, :"£", "£", '£'},
                  mode: :embedded,
                  node: release_node("runtime_config"),
                  protocols_consolidated?: true,