feat(fromEvent): add FromEvent type export (#19)

README.md

@@ -65,6 +65,23 @@ class MyEventEmitter<T> extends (EventEmitter as { new<T>(): TypedEmitter<T> })<
 }
 ```
 
+## RxJS `fromEvent` types inference
+
+The default `fromEvent` from RxJS will return an `Observable<unknown>` for our typed emitter.
+
+This can be fixed by the following code, by replacing the `fromEvent` type with our enhanced one: `FromEvent`:
+
+```ts
+import { fromEvent as rxFromEvent } from "rxjs"
+import { FromEvent } from "typed-emitter/rxjs"
+
+// The `Observable` typing can be correctly inferenced
+const fromEvent = rxFromEvent as FromEvent
+```
+
+Learn more from [rxjs fromEvent compatibility #9](https://github.com/andywer/typed-emitter/issues/9)
+for the `fromEvent` compatibility discussions.
+
 ## Why another package?
 
 The interface that comes with `@types/node` is not type-safe at all. It does not even offer a way of specifying the events that the emitter will emit...

index.d.ts

@@ -38,6 +38,12 @@ interface TypedEventEmitter<Events extends EventMap> {
 
   getMaxListeners (): number
   setMaxListeners (maxListeners: number): this
+
+  /**
+   * required by `FromEvent`
+   * @see https://github.com/devanshj/rxjs-from-emitter/issues/4#issuecomment-665104646
+   */
+  __events: Events
 }
 
 export default TypedEventEmitter

package.json

@@ -12,5 +12,8 @@
     "interface"
   ],
   "main": "./types.js",
-  "types": "./index.d.ts"
+  "types": "./index.d.ts",
+  "optionalDependencies": {
+    "rxjs": "*"
+  }
 }

rxjs/index.d.ts

@@ -0,0 +1,25 @@
+/**
+ * devanshj/rxjs-from-emitter#4 - typed-emitter compatibility
+ * 
+ * @see https://github.com/devanshj/rxjs-from-emitter/issues/4#issuecomment-665104646
+ */
+/* eslint-disable no-use-before-define */
+import { 
+  fromEvent as rxFromEvent, 
+  Observable,
+} from 'rxjs'
+import type TypedEventEmitter from '../index'
+
+type ObservedValue<A extends unknown[]> =
+  A['length'] extends 0 ? void :
+  A['length'] extends 1 ? A[0] :
+  A
+
+interface FromTypedEvent {
+  <   Emitter extends TypedEventEmitter<any>
+    , EventName extends keyof Events
+    , Events = Emitter extends TypedEventEmitter<infer T> ? T : never
+  >(emitter: Emitter, event: EventName): Observable<ObservedValue<Events[EventName] extends (...args: infer A) => any ? A : never>>   
+}
+
+export type FromEvent = FromTypedEvent & typeof rxFromEvent

rxjs/index.js

@@ -0,0 +1 @@
+// https://github.com/octokit/openapi-types.ts/issues/16#issuecomment-772784156