fix(utils): handle CRLF when parsing MDX imports (#8606)

packages/docusaurus-utils/src/__tests__/markdownUtils.test.ts

@@ -130,6 +130,26 @@ describe('createExcerpt', () => {
     );
   });
 
+  it('creates excerpt for content with imports/exports declarations, with CRLF line endings', () => {
+    expect(
+      createExcerpt(
+        dedent`
+          import Component from '@site/src/components/Component';
+
+          export function ItemCol(props) {
+            return <Item {...props} className={'col col--6 margin-bottom--lg'}/>
+          }
+
+          Lorem **ipsum** dolor sit \`amet\`[^1], consectetur _adipiscing_ elit. [**Vestibulum**](https://wiktionary.org/wiki/vestibulum) ex urna[^note], ~~molestie~~ et sagittis ut, varius ac justo :wink:.
+
+          Nunc porttitor libero nec vulputate venenatis. Nam nec rhoncus mauris. Morbi tempus est et nibh maximus, tempus venenatis arcu lobortis.
+        `.replace(/\n/g, '\r\n'),
+      ),
+    ).toBe(
+      'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum ex urna, molestie et sagittis ut, varius ac justo.',
+    );
+  });
+
   it('creates excerpt for heading specified with anchor-id syntax', () => {
     expect(
       createExcerpt(dedent`

packages/docusaurus-utils/src/markdownUtils.ts

@@ -55,16 +55,18 @@ export function createExcerpt(fileString: string): string | undefined {
   const fileLines = fileString
     .trimStart()
     // Remove Markdown alternate title
-    .replace(/^[^\n]*\n[=]+/g, '')
+    .replace(/^[^\r\n]*\r?\n[=]+/g, '')
-    .split('\n');
+    .split(/\r?\n/);
   let inCode = false;
   let inImport = false;
   let lastCodeFence = '';
 
   for (const fileLine of fileLines) {
-    if (fileLine === '' && inImport) {
+    // An empty line marks the end of imports
+    if (!fileLine.trim() && inImport) {
       inImport = false;
     }
+
     // Skip empty line.
     if (!fileLine.trim()) {
       continue;