fix(theme): Fix code block magic comments with CRLF line breaks bug (#11046)

* fix: with CRLF line breaks, an extra empty line was rendered with // highlight-end at end of code blocks

See: #11036

* Add unit tests

---------

Co-authored-by: sebastien <lorber.sebastien@gmail.com>

packages/docusaurus-theme-common/src/utils/__tests__/__snapshots__/codeBlockUtils.test.ts.snap

@@ -70,6 +70,30 @@ bbbbb",
 }
 `;
 
+exports[`parseLines handles CRLF line breaks with highlight comments correctly 1`] = `
+{
+  "code": "aaaaa
+bbbbb",
+  "lineClassNames": {
+    "1": [
+      "theme-code-block-highlighted-line",
+    ],
+  },
+}
+`;
+
+exports[`parseLines handles CRLF line breaks with highlight metastring 1`] = `
+{
+  "code": "aaaaa
+bbbbb",
+  "lineClassNames": {
+    "1": [
+      "theme-code-block-highlighted-line",
+    ],
+  },
+}
+`;
+
 exports[`parseLines handles one line with multiple class names 1`] = `
 {
   "code": "

packages/docusaurus-theme-common/src/utils/__tests__/codeBlockUtils.test.ts

@@ -360,6 +360,29 @@ line
       ),
     ).toMatchSnapshot();
   });
+
+  it('handles CRLF line breaks with highlight comments correctly', () => {
+    expect(
+      parseLines(
+        `aaaaa\r\n// highlight-start\r\nbbbbb\r\n// highlight-end\r\n`,
+        {
+          metastring: '',
+          language: 'js',
+          magicComments: defaultMagicComments,
+        },
+      ),
+    ).toMatchSnapshot();
+  });
+
+  it('handles CRLF line breaks with highlight metastring', () => {
+    expect(
+      parseLines(`aaaaa\r\nbbbbb\r\n`, {
+        metastring: '{2}',
+        language: 'js',
+        magicComments: defaultMagicComments,
+      }),
+    ).toMatchSnapshot();
+  });
 });
 
 describe('getLineNumbersStart', () => {

packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts

@@ -241,7 +241,7 @@ export function parseLines(
    */
   code: string;
 } {
-  let code = content.replace(/\n$/, '');
+  let code = content.replace(/\r?\n$/, '');
   const {language, magicComments, metastring} = options;
   // Highlighted lines specified in props: don't parse the content
   if (metastring && metastringLinesRangeRegex.test(metastring)) {
@@ -266,7 +266,7 @@ export function parseLines(
     magicComments,
   );
   // Go through line by line
-  const lines = code.split('\n');
+  const lines = code.split(/\r?\n/);
   const blocks = Object.fromEntries(
     magicComments.map((d) => [d.className, {start: 0, range: ''}]),
   );