From 8caeee8221e78c2412d8aeb9a7db7cc43abfdf1b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marin=20Petruni=C4=87?= <mpetrunic@users.noreply.github.com>
Date: Tue, 17 Jan 2023 17:45:58 +0100
Subject: [PATCH] feat: safe dispatch event (#319)

Adds a type-safe `safeDispatchEvent` method to the `EventEmitter` interface that allows type checking of dispatched events.

resolves #317

Co-authored-by: Alex Potsides <alex@achingbrain.net>
---
 packages/interface-mocks/src/connection-manager.ts | 10 +++++-----
 packages/interface-mocks/src/peer-discovery.ts     |  6 +++---
 packages/interfaces/src/events.ts                  |  4 ++++
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/packages/interface-mocks/src/connection-manager.ts b/packages/interface-mocks/src/connection-manager.ts
index 3768b49e0..5b2beadae 100644
--- a/packages/interface-mocks/src/connection-manager.ts
+++ b/packages/interface-mocks/src/connection-manager.ts
@@ -1,4 +1,4 @@
-import { CustomEvent, EventEmitter } from '@libp2p/interfaces/events'
+import { EventEmitter } from '@libp2p/interfaces/events'
 import type { Startable } from '@libp2p/interfaces/startable'
 import type { Connection } from '@libp2p/interface-connection'
 import type { PeerId } from '@libp2p/interface-peer-id'
@@ -99,9 +99,9 @@ class MockConnectionManager extends EventEmitter<ConnectionManagerEvents> implem
     this.connections.push(aToB)
     ;(componentsB.connectionManager as MockConnectionManager).connections.push(bToA)
 
-    this.components.connectionManager?.dispatchEvent(new CustomEvent<Connection>('peer:connect', {
+    this.components.connectionManager?.safeDispatchEvent<Connection>('peer:connect', {
       detail: aToB
-    }))
+    })
 
     for (const protocol of this.components.registrar.getProtocols()) {
       for (const topology of this.components.registrar.getTopologies(protocol)) {
@@ -109,9 +109,9 @@ class MockConnectionManager extends EventEmitter<ConnectionManagerEvents> implem
       }
     }
 
-    componentsB.connectionManager?.dispatchEvent(new CustomEvent<Connection>('peer:connect', {
+    componentsB.connectionManager?.safeDispatchEvent<Connection>('peer:connect', {
       detail: bToA
-    }))
+    })
 
     for (const protocol of componentsB.registrar.getProtocols()) {
       for (const topology of componentsB.registrar.getTopologies(protocol)) {
diff --git a/packages/interface-mocks/src/peer-discovery.ts b/packages/interface-mocks/src/peer-discovery.ts
index dd751478b..ff812786e 100644
--- a/packages/interface-mocks/src/peer-discovery.ts
+++ b/packages/interface-mocks/src/peer-discovery.ts
@@ -1,6 +1,6 @@
 import { multiaddr } from '@multiformats/multiaddr'
 import * as PeerIdFactory from '@libp2p/peer-id-factory'
-import { EventEmitter, CustomEvent } from '@libp2p/interfaces/events'
+import { EventEmitter } from '@libp2p/interfaces/events'
 import type { PeerDiscovery, PeerDiscoveryEvents } from '@libp2p/interface-peer-discovery'
 import type { PeerInfo } from '@libp2p/interface-peer-info'
 import { symbol } from '@libp2p/interface-peer-discovery'
@@ -52,13 +52,13 @@ export class MockDiscovery extends EventEmitter<PeerDiscoveryEvents> implements
     PeerIdFactory.createEd25519PeerId()
       .then(peerId => {
         this._timer = setTimeout(() => {
-          this.dispatchEvent(new CustomEvent<PeerInfo>('peer', {
+          this.safeDispatchEvent<PeerInfo>('peer', {
             detail: {
               id: peerId,
               multiaddrs: [multiaddr('/ip4/127.0.0.1/tcp/8000')],
               protocols: []
             }
-          }))
+          })
         }, this.options.discoveryDelay ?? 1000)
       })
       .catch(() => {})
diff --git a/packages/interfaces/src/events.ts b/packages/interfaces/src/events.ts
index a1b2e2a35..d63726288 100644
--- a/packages/interfaces/src/events.ts
+++ b/packages/interfaces/src/events.ts
@@ -74,6 +74,10 @@ export class EventEmitter<EventMap extends { [s: string]: any }> extends EventTa
 
     return result
   }
+
+  safeDispatchEvent<Detail>(type: keyof EventMap, detail: CustomEventInit<Detail>): boolean {
+    return this.dispatchEvent(new CustomEvent<Detail>(type as string, detail))
+  }
 }
 
 /**