fix: improving typings and apis for creating events and filtering eve…

…nt in epics

.lintstagedrc.json

@@ -1,5 +1,5 @@
 {
   "*.{ts,tsx,json}": ["prettier --write"],
-  "*.{ts,tsx}": ["pnpm run lint --"],
+  "*.{ts,tsx}": ["eslint --cache --fix"],
   "package.json": "sort-package-json"
 }

package.json

@@ -65,14 +65,5 @@
   },
   "volta": {
     "node": "18.9.0"
-  },
-  "wallaby": {
-    "autoDetect": true,
-    "files": [
-      "src/**/*.ts"
-    ],
-    "test": [
-      "test/unit/*.spec.ts"
-    ]
   }
 }

src/createEvent.ts

@@ -9,20 +9,22 @@ import type { Event, EventCreator, PrepareCallback } from './types'
  * if an event is produced by the return event creator
  *
  * @param name The event type to use for created events.
- * @param prepareEvent (optional) a method that takes an object and returns { payload, meta? }.
+ * @param options (optional) a method that takes an object and returns { payload, meta? }.
  *                If this is given, the resulting event creator will pass its arguments to this method to calculate payload.
  * @template P The type of the `payload` attribute of the created events
  * @template V The type of the argument used to `prepare` the payload
  *
  * @returns An event creator
  */
-export const createEvent = <P, M = unknown, V = unknown>(
+export const createEvent = <P, M = undefined, V = undefined>(
   name: string,
-  prepareEvent?: PrepareCallback<P, M, V>,
-): EventCreator<P, M, V> => {
-  const creator = (value?: P | V) => {
-    if (prepareEvent) {
-      const prepared = prepareEvent(value as V)
+  options: Partial<{
+    prepare: PrepareCallback<P, M, V>
+  }> = {},
+) => {
+  const creator: EventCreator<P, M, V> = (value?) => {
+    if (options.prepare) {
+      const prepared = options.prepare(value as V)
 
       if (!('meta' in prepared) && !('payload' in prepared))
         throw Error(`
@@ -44,7 +46,7 @@ export const createEvent = <P, M = unknown, V = unknown>(
   }
 
   creator.type = name
-  creator.match = (event: Event) => event.type === name
+  creator.match = (event: Event<P>) => event.type === name
 
   return creator
 }

src/types.ts

@@ -10,9 +10,10 @@ import type { Observable, Subscription } from 'rxjs'
  * performed. The `type` field needs to be a `string`
  *
  * If you need some data to represent what happen, you are free to populate
- * the payload property of an event.
+ * the payload / meta property of an event.
  *
  * @template P the type of the event's `payload` property.
+ * @template M the type of the event's `meta` property.
  */
 export type Event<P = unknown, M = unknown> = { type: string; payload?: P; meta?: M }
 
@@ -86,8 +87,8 @@ export type Store<S> = {
  * @param value The argument used to prepare the event
  *
  * @template P The type of the `payload` field of the created events
- * @template V The type of the argument used to `prepare` the payload
  * @template M The type of the `meta` field of the created events
+ * @template V The type of the argument passed to the prepare callbacks
  */
 export type PrepareCallback<P, M, V> = (value: V) => Partial<Omit<Event<P, M>, 'type'>>
 
@@ -97,8 +98,8 @@ export type PrepareCallback<P, M, V> = (value: V) => Partial<Omit<Event<P, M>, '
  * @template P the `payload` type
  * @template V the type of the parameter passed to the prepared callback
  */
-export type EventCreator<P = unknown, M = unknown, V = unknown> = {
-  (value?: P | V): Event<P, M>
+export type EventCreator<P, M = undefined, V = undefined> = {
+  (value?: V extends undefined ? P : V): Event<P, M>
   type: string
   match: (event: Event<P, M>) => boolean
 }

test/unit/createEvents.spec.ts

@@ -2,7 +2,7 @@ import { describe, expect, it } from 'vitest'
 import { createEvent } from '../../src/createEvent'
 
 describe('Creating an event', () => {
-  it('should contain a property type with then name of the type', () => {
+  it('should contain a property type with the name of the type', () => {
     const creator = createEvent('someDomain')
 
     expect(creator.type).toEqual('someDomain')
@@ -36,23 +36,27 @@ describe('Creating an event', () => {
     })
   })
 
-  describe('with prepared callback', () => {
+  describe('with options', () => {
     it('should throw and error if callback does not generate proper object', () => {
-      expect(createEvent('error', () => ({}))).toThrowError()
+      expect(createEvent('error', { prepare: () => ({}) })).toThrowError()
     })
 
     it('should be able to construct an event with prepared payload', () => {
-      const creator = createEvent('someDomain', (value: string) => ({
-        payload: { depth: Number.parseInt(value) },
-      }))
+      const creator = createEvent('someDomain', {
+        prepare: (value: string) => ({
+          payload: { depth: Number.parseInt(value) },
+        }),
+      })
 
       expect(creator('42')).toEqual({ type: 'someDomain', payload: { depth: 42 } })
     })
 
     it('should be able to construct an event with prepared meta', () => {
-      const creator = createEvent('event-meta', (value: number) => ({
-        meta: value,
-      }))
+      const creator = createEvent('event-meta', {
+        prepare: (value: number) => ({
+          meta: value,
+        }),
+      })
 
       expect(creator(42)).toEqual({ type: 'event-meta', meta: 42 })
     })