fix(localize): include the last placeholder in parsed translation text (#38452)

When creating a `ParsedTranslation` from a set of message parts and
placeholder names a textual representation of the message is computed.
Previously the last placeholder and text segment were missing from this
computed message string.

PR Close #38452

Author: petebacondarwin

packages/localize/src/utils/src/translations.ts

@@ -113,7 +113,7 @@ export function parseTranslation(messageString: TargetMessage): ParsedTranslatio
 export function makeParsedTranslation(
     messageParts: string[], placeholderNames: string[] = []): ParsedTranslation {
   let messageString = messageParts[0];
-  for (let i = 0; i < placeholderNames.length - 1; i++) {
+  for (let i = 0; i < placeholderNames.length; i++) {
     messageString += `{$${placeholderNames[i]}}${messageParts[i + 1]}`;
   }
   return {

packages/localize/src/utils/test/translations_spec.ts

@@ -5,7 +5,7 @@
  * 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 {computeMsgId, makeTemplateObject, ParsedTranslation, parseTranslation, TargetMessage, translate} from '..';
+import {computeMsgId, makeParsedTranslation, makeTemplateObject, ParsedTranslation, parseTranslation, TargetMessage, translate} from '..';
 
 describe('utils', () => {
   describe('makeTemplateObject', () => {
@@ -22,6 +22,24 @@ describe('utils', () => {
     });
   });
 
+  describe('makeParsedTranslation()', () => {
+    it('should compute a template object from the parts', () => {
+      expect(makeParsedTranslation(['a', 'b', 'c'], ['ph1', 'ph2']).messageParts)
+          .toEqual(makeTemplateObject(['a', 'b', 'c'], ['a', 'b', 'c']));
+    });
+
+    it('should include the placeholder names', () => {
+      expect(makeParsedTranslation(['a', 'b', 'c'], ['ph1', 'ph2']).placeholderNames).toEqual([
+        'ph1', 'ph2'
+      ]);
+    });
+
+    it('should compute the message string from the parts and placeholder names', () => {
+      expect(makeParsedTranslation(['a', 'b', 'c'], ['ph1', 'ph2']).text)
+          .toEqual('a{$ph1}b{$ph2}c');
+    });
+  });
+
   describe('parseTranslation', () => {
     it('should extract the messageParts as a TemplateStringsArray', () => {
       const translation = parseTranslation('a{$one}b{$two}c');