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

@@ -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'
@@ -99,19 +99,19 @@ 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)) {
         topology.onConnect(componentsB.peerId, aToB)
       }
     }
 
-    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)) {

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(() => {})

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))
+  }
 }
 
 /**