Capture stylesheets designated as rel="preload" (rrweb-io#1374)

* feat(Snapshot): Capture stylesheets designated as `rel="preload"`

* fix(Snapshot): Harden asset file extension matching

* Add changeset

* chore: Lint

* Tweak regex, add try-catch block on URL constructor

.changeset/smooth-papayas-boil.md

@@ -0,0 +1,6 @@
+---
+'rrweb-snapshot': patch
+'rrweb': patch
+---
+
+Capture stylesheets designated as `rel="preload"`

packages/rrweb-snapshot/src/snapshot.ts

@@ -23,6 +23,7 @@ import {
   stringifyStylesheet,
   getInputType,
   toLowerCase,
+  extractFileExtension,
 } from './utils';
 
 let _id = 1;
@@ -847,7 +848,7 @@ function slimDOMExcluded(
         (sn.tagName === 'link' &&
           sn.attributes.rel === 'prefetch' &&
           typeof sn.attributes.href === 'string' &&
-          sn.attributes.href.endsWith('.js')))
+          extractFileExtension(sn.attributes.href) === 'js'))
     ) {
       return true;
     } else if (
@@ -1177,7 +1178,11 @@ export function serializeNodeWithId(
   if (
     serializedNode.type === NodeType.Element &&
     serializedNode.tagName === 'link' &&
-    serializedNode.attributes.rel === 'stylesheet'
+    typeof serializedNode.attributes.rel === 'string' &&
+    (serializedNode.attributes.rel === 'stylesheet' ||
+      (serializedNode.attributes.rel === 'preload' &&
+        typeof serializedNode.attributes.href === 'string' &&
+        extractFileExtension(serializedNode.attributes.href) === 'css'))
   ) {
     onceStylesheetLoaded(
       n as HTMLLinkElement,

packages/rrweb-snapshot/src/utils.ts

@@ -331,3 +331,23 @@ export function getInputType(element: HTMLElement): Lowercase<string> | null {
       toLowerCase(type)
     : null;
 }
+
+/**
+ * Extracts the file extension from an a path, considering search parameters and fragments.
+ * @param path - Path to file
+ * @param baseURL - [optional] Base URL of the page, used to resolve relative paths. Defaults to current page URL.
+ */
+export function extractFileExtension(
+  path: string,
+  baseURL?: string,
+): string | null {
+  let url;
+  try {
+    url = new URL(path, baseURL ?? window.location.href);
+  } catch (err) {
+    return null;
+  }
+  const regex = /\.([0-9a-z]+)(?:$)/i;
+  const match = url.pathname.match(regex);
+  return match?.[1] ?? null;
+}

packages/rrweb-snapshot/test/utils.test.ts

@@ -3,7 +3,7 @@
  */
 import { serializedNodeWithId } from '@amplitude/rrweb-snapshot';
 import { NodeType, serializedNode } from '../src/types';
-import { isNodeMetaEqual } from '../src/utils';
+import { extractFileExtension, isNodeMetaEqual } from '../src/utils';
 
 describe('utils', () => {
   describe('isNodeMetaEqual()', () => {
@@ -147,4 +147,55 @@ describe('utils', () => {
       expect(isNodeMetaEqual(element2, element3)).toBeFalsy();
     });
   });
+  describe('extractFileExtension', () => {
+    test('absolute path', () => {
+      const path = 'https://example.com/styles/main.css';
+      const extension = extractFileExtension(path);
+      expect(extension).toBe('css');
+    });
+
+    test('relative path', () => {
+      const path = 'styles/main.css';
+      const baseURL = 'https://example.com/';
+      const extension = extractFileExtension(path, baseURL);
+      expect(extension).toBe('css');
+    });
+
+    test('path with search parameters', () => {
+      const path = 'https://example.com/scripts/app.js?version=1.0';
+      const extension = extractFileExtension(path);
+      expect(extension).toBe('js');
+    });
+
+    test('path with fragment', () => {
+      const path = 'https://example.com/styles/main.css#section1';
+      const extension = extractFileExtension(path);
+      expect(extension).toBe('css');
+    });
+
+    test('path with search parameters and fragment', () => {
+      const path = 'https://example.com/scripts/app.js?version=1.0#section1';
+      const extension = extractFileExtension(path);
+      expect(extension).toBe('js');
+    });
+
+    test('path without extension', () => {
+      const path = 'https://example.com/path/to/directory/';
+      const extension = extractFileExtension(path);
+      expect(extension).toBeNull();
+    });
+
+    test('invalid URL', () => {
+      const path = '!@#$%^&*()';
+      const baseURL = 'invalid';
+      const extension = extractFileExtension(path, baseURL);
+      expect(extension).toBeNull();
+    });
+
+    test('path with multiple dots', () => {
+      const path = 'https://example.com/scripts/app.min.js?version=1.0';
+      const extension = extractFileExtension(path);
+      expect(extension).toBe('js');
+    });
+  });
 });