feat: add extension_paths parameter for loading Chrome extensions (#210)

Add `extension_paths` parameter to all launch functions (Python + JS) for loading Chrome extensions.

Resolves paths to absolute, injects `--load-extension` and `--disable-extensions-except` flags via `build_args()`.

Note: Extensions require a persistent context (`launch_persistent_context`) to function — this is a Chromium limitation.

Co-authored-by: zackycodes <75211659+zackycodes@users.noreply.github.com>

js/src/args.ts

@@ -1,7 +1,7 @@
 /**
  * Shared argument builder for Playwright and Puppeteer wrappers.
  */
-
+import path from "path";
 import type { LaunchOptions } from "./types.js";
 import { getDefaultStealthArgs } from "./config.js";
 
@@ -55,5 +55,16 @@ export function buildArgs(options: LaunchOptions): string[] {
       seen.set(k, flag);
     }
   }
+
+  if (options.extensionPaths?.length) {
+    const absPaths = options.extensionPaths.map(p => path.resolve(p));
+    const joined = absPaths.join(",");
+
+    seen.set("--load-extension", `--load-extension=${joined}`);
+    seen.set(
+      "--disable-extensions-except",
+      `--disable-extensions-except=${joined}`
+    );
+  }
   return [...seen.values()];
 }

js/src/types.ts

@@ -17,6 +17,8 @@ export interface LaunchOptions {
   proxy?: string | { server: string; bypass?: string; username?: string; password?: string };
   /** Additional Chromium CLI arguments. */
   args?: string[];
+  /** Chrome extension paths to load. */
+  extensionPaths?: string[];
   /** Include default stealth fingerprint args (default: true). Set false to use custom --fingerprint flags. */
   stealthArgs?: boolean;
   /** IANA timezone, e.g. "America/New_York". Sets --fingerprint-timezone binary flag. */

js/tests/extension-loading.test.ts

@@ -0,0 +1,16 @@
+import path from "path";
+import { _buildArgsForTest } from "../src/playwright.js";
+
+test("extension paths inject chrome flags", () => {
+  const args = _buildArgsForTest({
+    extensionPaths: ["./ext"],
+  });
+
+  const abs = path.resolve("./ext");
+
+  expect(args).toContain(`--load-extension=${abs}`);
+
+  expect(args).toContain(
+    `--disable-extensions-except=${abs}`
+  );
+});