refactor(compiler): tighten the i18n placeholder name annotation regex

The regex that reads the name out of a `//i18n(ph="NAME")` annotation on an
interpolation expression chained five greedy `[\s\S]*` segments between the
literals `i18n`, `(`, `ph`, `=` and the opening quote. The separators in that
annotation are only ever whitespace, so bind them to `\s*`, and stop the name at
its own delimiter quote instead of letting it scan to the end of the input.

The loose pattern also had to try every way a run of `i18n(ph=` text could be
split across those wildcards, so rejecting an unterminated annotation took
exponential time: `'//' + 'i18n(ph='.repeat(200)` (~1.6 KB) took ~96s to
extract, and now resolves immediately.

Well-formed annotations resolve to the same name as before. The stricter pattern
does differ on malformed or repeated annotations, where the greedy wildcards
used to reach across them:

- `// i18n(ph="A") // i18n(ph="B")` resolves to `A` rather than `B`.
- `// i18n(ph="A"] )` is no longer recognized, since `]` is not whitespace.
- `// i18n(ph='say "hi"')` resolves to `say "hi"` rather than `hi`.

Author: arshsmith1

packages/compiler/src/i18n/i18n_parser.ts

@@ -453,8 +453,7 @@ ${nodes.map((node) => `"${node.sourceSpan.toString()}"`).join('\n')}
   }
 }
 
-const _CUSTOM_PH_EXP =
-  /\/\/[\s\S]*i18n[\s\S]*\([\s\S]*ph[\s\S]*=[\s\S]*("|')([\s\S]*?)\1[\s\S]*\)/g;
+const _CUSTOM_PH_EXP = /\/\/\s*i18n\s*\(\s*ph\s*=\s*("|')((?:(?!\1)[\s\S])*)\1\s*\)/g;
 
 function extractPlaceholderName(input: string): string {
   return input.split(_CUSTOM_PH_EXP)[2];

packages/compiler/test/i18n/i18n_parser_spec.ts

@@ -147,6 +147,17 @@ describe('I18nParser', () => {
         [[`[before, <ph name="TEST"> exp //i18n(ph='teSt') </ph>, after]`], 'm', 'd', ''],
       ]);
     });
+
+    it('should not backtrack on an unterminated placeholder annotation', () => {
+      // A `//i18n(ph=...` annotation that never closes must fall back to the default
+      // INTERPOLATION placeholder quickly instead of hanging while extracting the name.
+      const expression = '//' + 'i18n(ph='.repeat(200);
+      const start = Date.now();
+      expect(_humanizeMessages(`<div i18n="m|d">before{{ ${expression} }}after</div>`)).toEqual([
+        [[`[before, <ph name="INTERPOLATION"> ${expression} </ph>, after]`], 'm', 'd', ''],
+      ]);
+      expect(Date.now() - start).toBeLessThan(2000);
+    });
   });
 
   describe('blocks', () => {