Fix issue with GTS transform with backtick comments

src/parser/transforms.js

@@ -278,6 +278,11 @@ export const replaceRange = function replaceRange(s, start, end, substitute) {
   return s.slice(0, start) + substitute + s.slice(end);
 };
 
+function maskTemplateContentForLint(content) {
+  // Preserve line endings and UTF-16 length, but remove template syntax from the JS placeholder.
+  return content.replace(/[^\r\n]/g, ' ');
+}
+
 const processor = new Preprocessor();
 
 class EmberParserError extends Error {
@@ -332,7 +337,7 @@ export function transformForLint(code, fileName) {
   // Build placeholder JS inline (same format as ember-estree's toPlaceholderJS)
   let jsCode = code;
   for (const tplInfo of [...result].reverse()) {
-    const content = tplInfo.contents.replace(/`/g, '\\`').replace(/\$/g, '\\$');
+    const content = maskTemplateContentForLint(tplInfo.contents);
     const start = tplInfo.range.startUtf16Codepoint;
     const end = tplInfo.range.endUtf16Codepoint;
     const tplLength = end - start;

tests/parser.test.js

@@ -1,7 +1,7 @@
 import { beforeAll, describe, expect, it } from 'vitest';
 import { parseForESLint } from '../src/parser/gjs-gts-parser.js';
 import { replaceExtensions } from '../src/parser/ts-patch.js';
-import { traverse } from '../src/parser/transforms.js';
+import { transformForLint, traverse } from '../src/parser/transforms.js';
 import { SourceCode } from 'eslint';
 import { visitorKeys as tsVisitors } from '@typescript-eslint/visitor-keys';
 import { visitorKeys as glimmerVisitorKeys } from '@glimmer/syntax';
@@ -2384,6 +2384,23 @@ export const NotFound = <template>
     }
   });
 
+  it('transforms class templates with backtick-only comments for linting', () => {
+    const code = [
+      "import Component from '@glimmer/component';",
+      '',
+      'export default class MyComponent extends Component {',
+      '  <template>',
+      '    {{!  `asd` `qwe` `zxc` `undefined` `asd` }}',
+      '    {{! `@foo` }}',
+      '  </template>',
+      '}',
+    ].join('\n');
+
+    const { output } = transformForLint(code, 'example.gts');
+
+    expect(output).toHaveLength(code.length);
+  });
+
   it('svg elements are not added to global scope', () => {
     result = parseForESLint(
       `<template>