Add support for TS in boot script

gulpfile.mjs

@@ -109,7 +109,7 @@ gulp.task('watch-boot-script', () => {
       //
       // We could alternatively use `watchJS` to rebuild the bundle, but we'd
       // need to make its logging less noisy first.
-      'src/boot/**/*.js',
+      'src/boot/**/*.{js,ts,tsx}',
     ],
     { delay: 500 },
     gulp.task('build-boot-script')

rollup-boot.config.mjs

@@ -64,11 +64,11 @@ export default {
       // Rollup docs recommend against "inline", but for this tiny bundle it
       // produces a prod bundle of the same size and dev bundle that has less cruft in it.
       babelHelpers: 'inline',
-
       exclude: 'node_modules/**',
+      extensions: ['.js', '.ts', '.tsx']
     }),
     json(),
-    nodeResolve(),
+    nodeResolve({ extensions: ['.js', '.ts', '.tsx'] }),
     ...prodPlugins,
   ],
 };

src/boot/.babelrc

 {
   "presets": [
+    "@babel/preset-typescript",
     ["@babel/preset-env", {
        "targets": {
          "chrome": "40",

src/boot/browser-extension-utils.js → src/boot/browser-extension-utils.ts

 /**
  * Returns the extension ID which is running this script, or undefined if this
  * script is not being run by the browser extension.
- *
- * @param {Window} window_
- * @return {string | undefined}
  */
-export function getExtensionId(window_ = window) {
-  return /** @type {any} */ (window_).chrome?.runtime?.id;
+export function getExtensionId(window_: Window = window): string | undefined {
+  return (window_ as any).chrome?.runtime?.id;
 }
 
 /**
  * Verifies if there's a config script in the document that was generated by a
  * specific browser extension.
- *
- * @param {string} extensionId
- * @param {Document} document_
- * @return {boolean}
  */
-export function hasExtensionConfig(extensionId, document_ = document) {
+export function hasExtensionConfig(
+  extensionId: string,
+  document_: Document = document
+): boolean {
   return !!document_.querySelector(
     `script.js-hypothesis-config[data-extension-id=${extensionId}]`
   );