Keep :erts in release applications without colliding with the ERTS copy

lib/mix/lib/mix/release.ex

@@ -174,7 +174,7 @@ defmodule Mix.Release do
       version_path: Path.join([path, "releases", version]),
       erts_source: erts_source,
       erts_version: erts_version,
-      applications: Map.delete(loaded_apps, :erts),
+      applications: loaded_apps,
       boot_scripts: %{start: start_boot, start_clean: start_clean_boot},
       config_providers: config_providers,
       options: opts,

lib/mix/lib/mix/tasks/release.ex

@@ -1131,8 +1131,8 @@ defmodule Mix.Tasks.Release do
     {consolidation_path, release} = build_rel(release, config)
 
     [
-      # erts-VSN/
-      :erts,
+      # erts-VSN/ - written as __MODULE__ to avoid conflicting with :erts app
+      __MODULE__,
       # releases/VERSION/consolidated
       {:consolidated, consolidation_path},
       # bin/
@@ -1392,7 +1392,7 @@ defmodule Mix.Tasks.Release do
 
   ## Copy operations
 
-  defp copy(:erts, release) do
+  defp copy(__MODULE__, release) do
     _ = Mix.Release.copy_erts(release)
     :ok
   end

lib/mix/test/mix/release_test.exs

@@ -84,9 +84,10 @@ defmodule Mix.ReleaseTest do
       assert release.applications.kernel[:otp_app?]
     end
 
-    test "does not include erts in applications" do
+    test "includes erts in applications when requested" do
       release = from_config!(nil, config(releases: [foo: [applications: [erts: :permanent]]]), [])
-      assert release.applications[:erts] == nil
+      assert release.applications.erts[:otp_app?]
+      assert release.applications.erts[:vsn] == to_charlist(@erts_version)
     end
 
     test "allows release to be given as an anonymous function" do

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

@@ -370,6 +370,25 @@ defmodule Mix.Tasks.ReleaseTest do
     end)
   end
 
+  test "assembles a bootable release with :erts as one of its applications" do
+    in_fixture("release_test", fn ->
+      config = [releases: [release_test: [applications: [erts: :permanent]]]]
+
+      Mix.Project.in_project(:release_test, ".", config, fn _ ->
+        root = Path.absname("_build/dev/rel/release_test")
+        Mix.Task.run("release")
+
+        assert root |> Path.join("erts-#{@erts_version}/bin/erl") |> File.exists?()
+        assert root |> Path.join("lib/erts-#{@erts_version}/ebin/erts.app") |> File.exists?()
+
+        open_port(Path.join(root, "bin/release_test"), [~c"start"])
+
+        assert %{release_name: "release_test"} =
+                 wait_until_decoded(Path.join(root, "RELEASE_BOOTED"))
+      end)
+    end)
+  end
+
   test "assembles a rebootable release with runtime configuration" do
     in_fixture("release_test", fn ->
       config = [releases: [runtime_config: [reboot_system_after_config: true]]]