refactor(compiler): [i18n] integrate review feedback

modules/@angular/compiler/test/i18n/i18n_parser_spec.ts

@@ -291,7 +291,7 @@ export function main() {
   });
 }
 
-function _humanizeMessages(
+export function _humanizeMessages(
     html: string, implicitTags: string[] = [],
     implicitAttrs: {[k: string]: string[]} = {}): [string[], string, string][] {
   // clang-format off
@@ -322,7 +322,7 @@ function _humanizePlaceholdersToMessage(
 }
 
 
-function _extractMessages(
+export function _extractMessages(
     html: string, implicitTags: string[] = [],
     implicitAttrs: {[k: string]: string[]} = {}): Message[] {
   const htmlParser = new HtmlParser();

modules/@angular/compiler/test/i18n/serializers/i18n_ast_spec.ts

@@ -0,0 +1,66 @@
+/**
+ * @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 * as i18n from '@angular/compiler/src/i18n/i18n_ast';
+
+import {serializeNodes} from '../../../src/i18n/digest';
+import {_extractMessages} from '../i18n_parser_spec';
+
+export function main(): void {
+  describe('i18n AST', () => {
+    describe('CloneVisitor', () => {
+      it('should clone an AST', () => {
+        const messages = _extractMessages(
+            '<div i18n="m|d">b{count, plural, =0 {{sex, select, male {m}}}}a</div>');
+        const nodes = messages[0].nodes;
+        const text = serializeNodes(nodes).join('');
+        expect(text).toEqual(
+            'b<ph icu name="ICU">{count, plural, =0 {[{sex, select, male {[m]}}]}}</ph>a');
+        const visitor = new i18n.CloneVisitor();
+        const cloneNodes = nodes.map(n => n.visit(visitor));
+        expect(serializeNodes(nodes)).toEqual(serializeNodes(cloneNodes));
+        nodes.forEach((n: i18n.Node, i: number) => {
+          expect(n).toEqual(cloneNodes[i]);
+          expect(n).not.toBe(cloneNodes[i]);
+        });
+      });
+    });
+
+    describe('RecurseVisitor', () => {
+      it('should visit all nodes', () => {
+        const visitor = new RecurseVisitor();
+        const container = new i18n.Container(
+            [
+              new i18n.Text('', null),
+              new i18n.Placeholder('', '', null),
+              new i18n.IcuPlaceholder(null, '', null),
+            ],
+            null);
+        const tag = new i18n.TagPlaceholder('', {}, '', '', [container], false, null);
+        const icu = new i18n.Icu('', '', {tag}, null);
+
+        icu.visit(visitor);
+        expect(visitor.textCount).toEqual(1);
+        expect(visitor.phCount).toEqual(1);
+        expect(visitor.icuPhCount).toEqual(1);
+      });
+    });
+  });
+}
+
+class RecurseVisitor extends i18n.RecurseVisitor {
+  textCount = 0;
+  phCount = 0;
+  icuPhCount = 0;
+
+  visitText(text: i18n.Text, context?: any): any { this.textCount++; }
+
+  visitPlaceholder(ph: i18n.Placeholder, context?: any): any { this.phCount++; }
+
+  visitIcuPlaceholder(ph: i18n.IcuPlaceholder, context?: any): any { this.icuPhCount++; }
+}