test(ivy): todo app only includes reflect-metadata in JIT mode (angular#24677)

Previously the todo app imported reflect-metadata, since it is a dependency
of JIT and the todo app tests run in both JIT and AOT modes. However, the
code doesn't get tree-shaken away in AOT mode.

This change adds a target //packages/core/test/bundling/util:reflect_metadata
which, depending on whether the compile flag is in JIT or AOT mode, either
includes reflect-metadata or is a no-op.

Not including reflect-metadata gets the compressed todo bundle down to 12.5 kB.

PR Close angular#24677

Author: alxhub

packages/core/test/bundling/todo/BUILD.bazel

@@ -14,6 +14,7 @@ ng_module(
     deps = [
         "//packages/common",
         "//packages/core",
+        "//packages/core/test/bundling/util:reflect_metadata",
     ],
 )
 
@@ -31,6 +32,7 @@ ng_rollup_bundle(
         ":todo",
         "//packages/common",
         "//packages/core",
+        "//packages/core/test/bundling/util:reflect_metadata",
     ],
 )
 

packages/core/test/bundling/todo/index.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import 'reflect-metadata';
+import '@angular/core/test/bundling/util/src/reflect_metadata';
 
 import {CommonModule, NgForOf, NgIf} from '@angular/common';
 import {Component, Injectable, IterableDiffers, NgModule, defineInjector, ɵNgOnChangesFeature as NgOnChangesFeature, ɵdefineDirective as defineDirective, ɵdirectiveInject as directiveInject, ɵinjectTemplateRef as injectTemplateRef, ɵinjectViewContainerRef as injectViewContainerRef, ɵrenderComponent as renderComponent} from '@angular/core';

packages/core/test/bundling/util/BUILD.bazel

@@ -0,0 +1,22 @@
+package(default_visibility = ["//visibility:public"])
+
+load("//tools:defaults.bzl", "ts_library")
+
+# Either loads reflect-metadata or is a no-op, depending on whether compilation is in JIT mode.
+ts_library(
+    name = "reflect_metadata",
+    srcs = [
+        "src/reflect_metadata_jit.ts",
+        "src/reflect_metadata_legacy.ts",
+        "src/reflect_metadata_local.ts",
+        ":metadata_switch",
+    ],
+    module_name = "@angular/core/test/bundling/util/src/reflect_metadata",
+)
+
+# See packages/core/BUILD.bazel.
+genrule(
+    name = "metadata_switch",
+    outs = ["src/reflect_metadata.ts"],
+    cmd = "echo import \"'./reflect_metadata_$(compile)';\" > $@",
+)

packages/core/test/bundling/util/src/reflect_metadata.ts

@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import './reflect_metadata_legacy';

packages/core/test/bundling/util/src/reflect_metadata_jit.ts

@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import 'reflect-metadata';

packages/core/test/bundling/util/src/reflect_metadata_legacy.ts

@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+export const UNUSED = true;

packages/core/test/bundling/util/src/reflect_metadata_local.ts

@@ -0,0 +1,9 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+export const UNUSED = true;