1 files changed, 71 insertions, 0 deletions
diff --git a/devtools/shared/async-utils.js b/devtools/shared/async-utils.js
new file mode 100644
index 0000000000..cb1fee1a4f
--- /dev/null
+++ b/devtools/shared/async-utils.js
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Helpers for async functions. An async function returns a Promise for the
+ * resolution of the function. When the function returns, the promise is
+ * resolved with the returned value. If it throws the promise rejects with
+ * the thrown error.
+ */
+
+/**
+ * Adds an event listener to the given element, and then removes its event
+ * listener once the event is called, returning the event object as a promise.
+ * @param  Element element
+ *         The DOM element to listen on
+ * @param  String event
+ *         The name of the event type to listen for
+ * @param  Boolean useCapture
+ *         Should we initiate the capture phase?
+ * @return Promise
+ *         The promise resolved with the event object when the event first
+ *         happens
+ */
+exports.listenOnce = function listenOnce(element, event, useCapture) {
+  return new Promise(function (resolve, reject) {
+    const onEvent = function (ev) {
+      element.removeEventListener(event, onEvent, useCapture);
+      resolve(ev);
+    };
+    element.addEventListener(event, onEvent, useCapture);
+  });
+};
+
+// Return value when `safeAsyncMethod` catches an error.
+const SWALLOWED_RET = Symbol("swallowed");
+
+/**
+ * Wraps the provided async method in a try/catch block.
+ * If an error is caught while running the method, check the provided condition
+ * to decide whether the error should bubble or not.
+ *
+ * @param  {Function} asyncFn
+ *         The async method to wrap.
+ * @param  {Function} shouldSwallow
+ *         Function that will run when an error is caught. If it returns true,
+ *         the error will be swallowed. Otherwise, it will bubble up.
+ * @param {Mixed} retValue
+ *         Optional value to return when an error is caught and is swallowed.
+ * @return {Function} The wrapped method.
+ */
+exports.safeAsyncMethod = function (
+  asyncFn,
+  shouldSwallow,
+  retValue = SWALLOWED_RET
+) {
+  return async function (...args) {
+    try {
+      const ret = await asyncFn(...args);
+      return ret;
+    } catch (e) {
+      if (shouldSwallow()) {
+        console.warn("Async method failed in safeAsyncMethod", e);
+        return retValue;
+      }
+      throw e;
+    }
+  };
+};