feat(tsc-wrapped): add an option to ngc to bundle metadata (#14509)

Closes #14509

tools/@angular/tsc-wrapped/src/index_writer.ts

@@ -0,0 +1,58 @@
+/**
+ * @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 {BundlePrivateEntry} from './bundler';
+
+const INDEX_HEADER = `/**
+ * Generated bundle index. Do not edit.
+ */
+`;
+
+type MapEntry = [string, BundlePrivateEntry[]];
+
+export function privateEntriesToIndex(index: string, privates: BundlePrivateEntry[]): string {
+  const results: string[] = [INDEX_HEADER];
+
+  // Export all of the index symbols.
+  results.push(`export * from '${index}';`, '');
+
+  // Simplify the exports
+  const exports = new Map<string, BundlePrivateEntry[]>();
+
+  for (const entry of privates) {
+    let entries = exports.get(entry.module);
+    if (!entries) {
+      entries = [];
+      exports.set(entry.module, entries);
+    }
+    entries.push(entry);
+  }
+
+
+  const compareEntries = compare((e: BundlePrivateEntry) => e.name);
+  const compareModules = compare((e: MapEntry) => e[0]);
+  const orderedExports =
+      Array.from(exports)
+          .map(([module, entries]) => <MapEntry>[module, entries.sort(compareEntries)])
+          .sort(compareModules);
+
+  for (const [module, entries] of orderedExports) {
+    let symbols = entries.map(e => `${e.name} as ${e.privateName}`);
+    results.push(`export {${symbols}} from '${module}';`);
+  }
+
+  return results.join('\n');
+}
+
+function compare<E, T>(select: (e: E) => T): (a: E, b: E) => number {
+  return (a, b) => {
+    const ak = select(a);
+    const bk = select(b);
+    return ak > bk ? 1 : ak < bk ? -1 : 0;
+  };
+}