Improve how we detect if the boot script is run by certain browser extension

src/boot/browser-extension-utils.js

+/**
+ * Tries to get 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;
+}
+
+/**
+ * Verifies if there's a config script in the document that was generated by a
+ * specific extension
+ *
+ * @param {string} extensionId
+ * @param {Document} document_
+ * @return {boolean}
+ */
+export function hasExtensionConfig(extensionId, document_ = document) {
+  return !!document_.querySelector(
+    `script.js-hypothesis-config[data-extension-id=${extensionId}]`
+  );
+}

src/boot/index.js

@@ -9,6 +9,7 @@
 import manifest from '../../build/manifest.json';
 import { bootHypothesisClient, bootSidebarApp } from './boot';
 import { isBrowserSupported } from './browser-check';
+import { getExtensionId, hasExtensionConfig } from './browser-extension-utils';
 import { parseJsonConfig } from './parse-json-config';
 import { processUrlTemplate } from './url-template';
 
@@ -22,12 +23,10 @@ if (isBrowserSupported()) {
     parseJsonConfig(document)
   );
 
-  // When the boot script is executed from the browser extension, at least one
-  // config is required
-  const isExtensionContext = !!(
-    /** @type {any} */ (window).chrome?.runtime?.id
-  );
-  if (!Object.keys(config).length && isExtensionContext) {
+  // When the boot script is executed from the browser extension, a config
+  // generated by that specific extension is required
+  const extensionId = getExtensionId();
+  if (extensionId && !hasExtensionConfig(extensionId)) {
     throw new Error(
       'Could not start Hypothesis extension as configuration is missing'
     );