Add latest changes from gitlab-org/gitlab@master

1 files changed, 85 insertions, 2 deletions

diff --git a/app/assets/javascripts/helpers/event_hub_factory.js b/app/assets/javascripts/helpers/event_hub_factory.js
index 863f490a63e..a9c301e3a93 100644
--- a/app/assets/javascripts/helpers/event_hub_factory.js
+++ b/app/assets/javascripts/helpers/event_hub_factory.js
@@ -1,4 +1,87 @@
-import Vue from 'vue';
+/**
+ * An event hub with a Vue instance like API
+ *
+ * NOTE: There's an [issue open][4] to eventually remove this when some
+ * coupling in our codebase has been fixed.
+ *
+ * NOTE: This is a derivative work from [mitt][1] v1.2.0 which is licensed by
+ * [MIT License][2] © [Jason Miller][3]
+ *
+ * [1]: https://github.com/developit/mitt
+ * [2]: https://opensource.org/licenses/MIT
+ * [3]: https://jasonformat.com/
+ * [4]: https://gitlab.com/gitlab-org/gitlab/-/issues/223864
+ */
+class EventHub {
+  constructor() {
+    this.$_all = new Map();
+  }
+
+  dispose() {
+    this.$_all.clear();
+  }
+
+  /**
+   * Register an event handler for the given type.
+   *
+   * @param {string|symbol} type Type of event to listen for
+   * @param {Function} handler Function to call in response to given event
+   */
+  $on(type, handler) {
+    const handlers = this.$_all.get(type);
+    const added = handlers && handlers.push(handler);
+
+    if (!added) {
+      this.$_all.set(type, [handler]);
+    }
+  }
+
+  /**
+   * Remove an event handler or all handlers for the given type.
+   *
+   * @param {string|symbol} type Type of event to unregister `handler`
+   * @param {Function} handler Handler function to remove
+   */
+  $off(type, handler) {
+    const handlers = this.$_all.get(type) || [];
+
+    const newHandlers = handler ? handlers.filter(x => x !== handler) : [];
+
+    if (newHandlers.length) {
+      this.$_all.set(type, newHandlers);
+    } else {
+      this.$_all.delete(type);
+    }
+  }
+
+  /**
+   * Add an event listener to type but only trigger it once
+   *
+   * @param {string|symbol} type Type of event to listen for
+   * @param {Function} handler Handler function to call in response to event
+   */
+  $once(type, handler) {
+    const wrapHandler = (...args) => {
+      this.$off(type, wrapHandler);
+      handler(...args);
+    };
+    this.$on(type, wrapHandler);
+  }
+
+  /**
+   * Invoke all handlers for the given type.
+   *
+   * @param {string|symbol} type The event type to invoke
+   * @param {Any} [evt] Any value passed to each handler
+   */
+  $emit(type, ...args) {
+    const handlers = this.$_all.get(type) || [];
+
+    handlers.forEach(handler => {
+      handler(...args);
+    });
+  }
+}
 
 /**
  * Return a Vue like event hub
@@ -14,5 +97,5 @@ import Vue from 'vue';
  * We'd like to shy away from using a full fledged Vue instance from this in the future.
  */
 export default () => {
-  return new Vue();
+  return new EventHub();
 };