fix(localize): render correct closing tag placeholder names in XLIFF 2 (#41152)

When there are elements in a translated message, the start and end tags
are encoded as placeholders. The names of these placeholders are computed
from the name of the element. For example `<a> will be `START_LINK` and
`</a>` will be `CLOSE_LINK`.

If there are more than one element with the same name, but different attributes,
then the starting placeholder name is made unique.
For example `<a href="a">` would be `START_LINK`, while `<a href="b">` in
the same message would then be called `START_LINK_1`.
But the closing tags will not be made unique since there are no attrbutes;
the always have the same text `</a>`, which will produce, for example,
`CLOSE_LINK`.

Previously, when extracting XLIFF 2 formatted translation files, the closing
tag placeholder names were computed incorrectly from the opening tag
placeholder names. For example `CLOSE_LINK_1`.

This commit strips these `_1` type endings from the start tag placeholder
name when computing the closing tag placeholder name. It also ensures
that the `type` of the placeholder is computed accurately in these cases
too.

Fixes #41142

PR Close #41152

packages/localize/src/tools/src/extract/translation_files/xliff2_translation_serializer.ts

@@ -113,7 +113,9 @@ export class Xliff2TranslationSerializer implements TranslationSerializer {
     const text = substitutionLocations?.[placeholderName]?.text;
 
     if (placeholderName.startsWith('START_')) {
-      const closingPlaceholderName = placeholderName.replace(/^START/, 'CLOSE');
+      // Replace the `START` with `CLOSE` and strip off any `_1` ids from the end.
+      const closingPlaceholderName =
+          placeholderName.replace(/^START/, 'CLOSE').replace(/_\d+$/, '');
       const closingText = substitutionLocations?.[closingPlaceholderName]?.text;
       const attrs: Record<string, string> = {
         id: `${this.currentPlaceholderId++}`,
@@ -186,7 +188,7 @@ export class Xliff2TranslationSerializer implements TranslationSerializer {
  * and links are special cases.
  */
 function getTypeForPlaceholder(placeholder: string): string|null {
-  const tag = placeholder.replace(/^(START_|CLOSE_)/, '');
+  const tag = placeholder.replace(/^(START_|CLOSE_)/, '').replace(/_\d+$/, '');
   switch (tag) {
     case 'BOLD_TEXT':
     case 'EMPHASISED_TEXT':

packages/localize/src/tools/test/extract/translation_files/xliff2_translation_serializer_spec.ts

@@ -301,6 +301,27 @@ runInEachFileSystem(() => {
                 '<source>a<pc id="0" equivStart="START_TAG_DIV" equivEnd="CLOSE_TAG_DIV" type="other">b</pc>c</source>',
             );
           });
+
+          it('should render the "type" for link elements', () => {
+            const serializer = new Xliff2TranslationSerializer(
+                'xx', absoluteFrom('/project'), useLegacyIds, options);
+            const output = serializer.serialize(
+                [mockMessage('6', ['a', 'b', 'c'], ['START_LINK', 'CLOSE_LINK'], {})]);
+            expect(output).toContain(
+                '<source>a<pc id="0" equivStart="START_LINK" equivEnd="CLOSE_LINK" type="link">b</pc>c</source>',
+            );
+          });
+
+          it('should render generic close tag placeholders for additional elements', () => {
+            const serializer = new Xliff2TranslationSerializer(
+                'xx', absoluteFrom('/project'), useLegacyIds, options);
+            const output = serializer.serialize([mockMessage(
+                '6', ['a', 'b', 'c', 'd', 'e'],
+                ['START_LINK', 'CLOSE_LINK', 'START_LINK_1', 'CLOSE_LINK'], {})]);
+            expect(output).toContain(
+                '<source>a<pc id="0" equivStart="START_LINK" equivEnd="CLOSE_LINK" type="link">b</pc>c<pc id="1" equivStart="START_LINK_1" equivEnd="CLOSE_LINK" type="link">d</pc>e</source>',
+            );
+          });
         });
       });
     });