fix(network, DHT): stricter typing for event listeners in interfaces

packages/dht/src/dht/DhtNode.ts

@@ -54,7 +54,7 @@ import { StoreManager } from './store/StoreManager'
 import { StoreRpcRemote } from './store/StoreRpcRemote'
 import { getLocalRegionByCoordinates, getLocalRegionWithCache } from '@streamr/cdn-location'
 
-export interface DhtNodeEvents {
+export interface DhtNodeEvents extends TransportEvents {
     nearbyContactAdded: (peerDescriptor: PeerDescriptor) => void
     nearbyContactRemoved: (peerDescriptor: PeerDescriptor) => void
     randomContactAdded: (peerDescriptor: PeerDescriptor) => void
@@ -133,9 +133,7 @@ const PERIODICAL_PING_INTERVAL = 60 * 1000
 // TODO move this to trackerless-network package and change serviceId to be a required paramater
 export const CONTROL_LAYER_NODE_SERVICE_ID = 'layer0'
 
-export type Events = TransportEvents & DhtNodeEvents
-
-export class DhtNode extends EventEmitter<Events> implements ITransport {
+export class DhtNode extends EventEmitter<DhtNodeEvents> implements ITransport {
 
     private readonly options: StrictDhtNodeOptions
     private rpcCommunicator?: RoutingRpcCommunicator

packages/dht/src/transport/ITransport.ts

@@ -1,9 +1,10 @@
 import { Message, PeerDescriptor } from '../../generated/packages/dht/protos/DhtRpc'
+import { EventEmitterType } from '@streamr/utils'
 
 export interface TransportEvents {
+    connected: (peerDescriptor: PeerDescriptor) => void
     disconnected: (peerDescriptor: PeerDescriptor, gracefulLeave: boolean) => void
     message: (message: Message) => void
-    connected: (peerDescriptor: PeerDescriptor) => void
 }
 
 export interface SendOptions {
@@ -18,20 +19,7 @@ export const DEFAULT_SEND_OPTIONS = {
     doNotBufferWhileConnecting: false
 }
 
-export interface ITransport {
-    on<T extends keyof TransportEvents>(eventName: T, listener: (message: Message) => void): void
-    on<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    on<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor, gracefulLeave: boolean) => void): void
-
-    once<T extends keyof TransportEvents>(eventName: T, listener: (message: Message) => void): void
-    once<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    once<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor, 
-        gracefulLeave: boolean) => void): void
-
-    off<T extends keyof TransportEvents>(eventName: T, listener: (message: Message) => void): void
-    off<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    off<T extends keyof TransportEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor, gracefulLeave: boolean) => void): void
-
+export interface ITransport extends EventEmitterType<TransportEvents> {
     send(msg: Message, opts?: SendOptions): Promise<void>
     getLocalPeerDescriptor(): PeerDescriptor
     stop(): void | Promise<void>

packages/dht/test/integration/RouteMessage.test.ts

@@ -1,4 +1,4 @@
-import { DhtNode, Events as DhtNodeEvents } from '../../src/dht/DhtNode'
+import { DhtNode, DhtNodeEvents } from '../../src/dht/DhtNode'
 import { Message, PeerDescriptor, RouteMessageWrapper } from '../../generated/packages/dht/protos/DhtRpc'
 import { RpcMessage } from '../../generated/packages/proto-rpc/protos/ProtoRpc'
 import { Logger, runAndWaitForEvents3, until } from '@streamr/utils'

packages/trackerless-network/src/logic/ContentDeliveryLayerNode.ts

@@ -117,46 +117,48 @@ export class ContentDeliveryLayerNode extends EventEmitter<Events> {
         })
     }
 
+    /* eslint-disable indent */
+    // Linting for indentation is broken in addManagedEventListener for some reason.
     async start(): Promise<void> {
         this.started = true
         this.registerDefaultServerMethods()
-        addManagedEventListener(
+        addManagedEventListener<'nearbyContactAdded', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'nearbyContactAdded', 
             () => this.onNearbyContactAdded(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'nearbyContactRemoved', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'nearbyContactRemoved',
             () => this.onNearbyContactRemoved(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'randomContactAdded', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'randomContactAdded',
             () => this.onRandomContactAdded(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'randomContactRemoved', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'randomContactRemoved',
             () => this.onRandomContactRemoved(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'ringContactAdded', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'ringContactAdded',
             () => this.onRingContactsUpdated(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'ringContactRemoved', (node: PeerDescriptor) => void>(
             this.options.discoveryLayerNode,
             'ringContactRemoved',
             () => this.onRingContactsUpdated(),
             this.abortController.signal
         )
-        addManagedEventListener(
+        addManagedEventListener<'disconnected', (node: PeerDescriptor) => void>(
             this.options.transport,
             'disconnected',
             (peerDescriptor: PeerDescriptor) => this.onNodeDisconnected(peerDescriptor),

packages/trackerless-network/src/logic/DiscoveryLayerNode.ts

@@ -1,4 +1,5 @@
 import { DhtAddress, PeerDescriptor, RingContacts } from '@streamr/dht'
+import { EventEmitterType } from '@streamr/utils'
 
 export interface DiscoveryLayerNodeEvents {
     manualRejoinRequired: () => void
@@ -9,14 +10,7 @@ export interface DiscoveryLayerNodeEvents {
     ringContactAdded: (peerDescriptor: PeerDescriptor) => void
     ringContactRemoved: (peerDescriptor: PeerDescriptor) => void
 }
-
-export interface DiscoveryLayerNode {
-    on<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    on<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: () => void): void
-    off<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    off<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: () => void): void
-    once<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: (peerDescriptor: PeerDescriptor) => void): void
-    once<T extends keyof DiscoveryLayerNodeEvents>(eventName: T, listener: () => void): void
+export interface DiscoveryLayerNode extends EventEmitterType<DiscoveryLayerNodeEvents> {
     removeContact: (nodeId: DhtAddress) => void
     getClosestContacts: (maxCount?: number) => PeerDescriptor[]
     getRandomContacts: (maxCount?: number) => PeerDescriptor[]

packages/trackerless-network/src/logic/proxy/ProxyClient.ts

@@ -258,9 +258,11 @@ export class ProxyClient extends EventEmitter<Events> {
         }
     }
 
+    /* eslint-disable indent */
+    // Linting for indentation is broken in addManagedEventListener for some reason.
     async start(): Promise<void> {
         this.registerDefaultServerMethods()
-        addManagedEventListener(
+        addManagedEventListener<'disconnected', (node: PeerDescriptor) => void>(
             this.options.transport,
             'disconnected',
             // TODO should we catch possible promise rejection?

packages/utils/src/EventEmitterType.ts

@@ -0,0 +1,35 @@
+// Utility type EmitterOf<T>. By deriving an interface from this type, 
+// you declare that the interface has the standard EventEmitter3  
+// listener setter functions 'on', 'off', 'once' for each event type
+// defined in T.
+
+// Convert EventEmitter3 event types to corresponding listener
+// setter function types (eg. types of 'on', 'off', 'once').
+// For example, 
+// message: (payload: Payload) => void
+// -> message: (event: 'message', listener: (payload: Payload) => void) => void
+
+type ListenerSetterTypes<T> = {
+    [K in keyof T]: (event: K, listener: T[K]) => void
+}
+
+// In typescript, type of on overloaded function is
+// the intersection of the overloaded function types 
+// (https://stackoverflow.com/a/54887669).
+// The following code builds the intersection type
+// of the given listener setter function types
+// (https://stackoverflow.com/a/66445507).
+
+type Intersection<T> = {
+    [K in keyof T]: (x: T[K]) => void
+  }[keyof T] extends
+    (x: infer I) => void ? I : never
+
+type OverloadedListenerSetter<T> = Intersection<ListenerSetterTypes<T>> 
+
+// eslint-disable-next-line @typescript-eslint/consistent-type-definitions
+export type EventEmitterType<T> = {
+    on: OverloadedListenerSetter<T> 
+    off: OverloadedListenerSetter<T>
+    once: OverloadedListenerSetter<T>
+}

packages/utils/src/exports.ts

@@ -46,6 +46,7 @@ import { toLengthPrefixedFrame, LengthPrefixedFrameDecoder } from './lengthPrefi
 import { verifySignature, createSignature, recoverSignerUserId, hash } from './signingUtils'
 import { ipv4ToNumber, numberToIpv4 } from './ipv4ToNumber'
 import { MapWithTtl } from './MapWithTtl'
+import { EventEmitterType } from './EventEmitterType'
 
 export {
     BrandedString,
@@ -108,6 +109,7 @@ export {
     numberToIpv4,
     hash,
     MapWithTtl,
+    EventEmitterType,
     Cache
 }