fix(std/node): emitter.removeAllListeners (#5583)

When given a non-registered eventName to 
emitter.removeAllListeners(eventName), current code 
would remove all listeners instead of silently skip, 
which is not ideal.

2 files changed, 28 insertions, 7 deletions

diff --git a/std/node/events.ts b/std/node/events.ts
index cb9acb0f5..fee715f0c 100644
--- a/std/node/events.ts
+++ b/std/node/events.ts
@@ -279,13 +279,15 @@ export default class EventEmitter {
       return this;
     }
 
-    if (eventName && this._events.has(eventName)) {
-      const listeners = (this._events.get(eventName) as Array<
-        Function | WrappedFunction
-      >).slice(); // Create a copy; We use it AFTER it's deleted.
-      this._events.delete(eventName);
-      for (const listener of listeners) {
-        this.emit("removeListener", eventName, listener);
+    if (eventName) {
+      if (this._events.has(eventName)) {
+        const listeners = (this._events.get(eventName) as Array<
+          Function | WrappedFunction
+        >).slice(); // Create a copy; We use it AFTER it's deleted.
+        this._events.delete(eventName);
+        for (const listener of listeners) {
+          this.emit("removeListener", eventName, listener);
+        }
       }
     } else {
       const eventList: [string | symbol] = this.eventNames();
diff --git a/std/node/events_test.ts b/std/node/events_test.ts
index 3c3628e3a..4b47686f4 100644
--- a/std/node/events_test.ts
+++ b/std/node/events_test.ts
@@ -246,6 +246,25 @@ test({
 });
 
 test({
+  name: "Provide a non-existent event to removeAllListeners will do nothing",
+  fn() {
+    const testEmitter = new EventEmitter();
+    testEmitter.on("event", shouldNeverBeEmitted);
+    testEmitter.on("event", shouldNeverBeEmitted);
+    testEmitter.on("other event", shouldNeverBeEmitted);
+    testEmitter.on("other event", shouldNeverBeEmitted);
+    testEmitter.once("other event", shouldNeverBeEmitted);
+    assertEquals(testEmitter.listenerCount("event"), 2);
+    assertEquals(testEmitter.listenerCount("other event"), 3);
+
+    testEmitter.removeAllListeners("non-existent");
+
+    assertEquals(testEmitter.listenerCount("event"), 2);
+    assertEquals(testEmitter.listenerCount("other event"), 3);
+  },
+});
+
+test({
   name: "Remove individual listeners, which can also be chained",
   fn() {
     const testEmitter = new EventEmitter();