From 21aeded2eaa0e597b70510a48cf8fd8c9f978476 Mon Sep 17 00:00:00 2001
From: Andrew Bastin <andrewbastin.k@gmail.com>
Date: Tue, 25 May 2021 18:27:50 -0400
Subject: [PATCH] Update DispatchingStore to provide better typing for dispatch
 function parameters

---
 newstore/DispatchingStore.ts | 36 +++++++++++++++++++++---------------
 newstore/history.ts          | 17 ++++++++++-------
 newstore/settings.ts         | 14 ++++++++------
 3 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/newstore/DispatchingStore.ts b/newstore/DispatchingStore.ts
index e32b48f30..4406cdbc2 100644
--- a/newstore/DispatchingStore.ts
+++ b/newstore/DispatchingStore.ts
@@ -3,28 +3,37 @@ import { map } from "rxjs/operators"
 import assign from "lodash/assign"
 import clone from "lodash/clone"
 
-export type Dispatchers<StoreType> = {
-  [key: string]: (currentVal: StoreType, payload: any) => Partial<StoreType>
-}
+type dispatcherFunc<StoreType> = (
+  currentVal: StoreType,
+  payload: any
+) => Partial<StoreType>
+
+/**
+ * Defines a dispatcher.
+ *
+ * This function exists to provide better typing for dispatch function.
+ * As you can see, its pretty much an identity function.
+ */
+export const defineDispatchers = <StoreType, T>(
+  // eslint-disable-next-line no-unused-vars
+  dispatchers: { [_ in keyof T]: dispatcherFunc<StoreType> }
+) => dispatchers
 
 type Dispatch<
   StoreType,
-  DispatchersType extends Dispatchers<StoreType>,
-  K extends keyof DispatchersType
+  DispatchersType extends Record<string, dispatcherFunc<StoreType>>
 > = {
-  dispatcher: K & string
+  dispatcher: keyof DispatchersType
   payload: any
 }
 
 export default class DispatchingStore<
   StoreType,
-  DispatchersType extends Dispatchers<StoreType>
+  DispatchersType extends Record<string, dispatcherFunc<StoreType>>
 > {
   #state$: BehaviorSubject<StoreType>
-  #dispatchers: Dispatchers<StoreType>
-  #dispatches$: Subject<
-    Dispatch<StoreType, DispatchersType, keyof DispatchersType>
-  > = new Subject()
+  #dispatchers: DispatchersType
+  #dispatches$: Subject<Dispatch<StoreType, DispatchersType>> = new Subject()
 
   constructor(initialValue: StoreType, dispatchers: DispatchersType) {
     this.#state$ = new BehaviorSubject(initialValue)
@@ -56,10 +65,7 @@ export default class DispatchingStore<
     return this.#dispatches$
   }
 
-  dispatch({
-    dispatcher,
-    payload,
-  }: Dispatch<StoreType, DispatchersType, keyof DispatchersType>) {
+  dispatch({ dispatcher, payload }: Dispatch<StoreType, DispatchersType>) {
     if (!this.#dispatchers[dispatcher])
       throw new Error(`Undefined dispatch type '${dispatcher}'`)
 
diff --git a/newstore/history.ts b/newstore/history.ts
index e88c02d83..3a9f5705a 100644
--- a/newstore/history.ts
+++ b/newstore/history.ts
@@ -1,6 +1,6 @@
 import eq from "lodash/eq"
 import { pluck } from "rxjs/operators"
-import DispatchingStore, { Dispatchers } from "./DispatchingStore"
+import DispatchingStore, { defineDispatchers } from "./DispatchingStore"
 
 export const defaultRESTHistoryState = {
   state: [] as any[],
@@ -15,18 +15,21 @@ export const HISTORY_LIMIT = 50
 type RESTHistoryType = typeof defaultRESTHistoryState
 type GraphqlHistoryType = typeof defaultGraphqlHistoryState
 
-const HistoryDispatcher: Dispatchers<RESTHistoryType | GraphqlHistoryType> = {
-  setEntries(_, { entries }: { entries: any[] }) {
+const HistoryDispatcher = defineDispatchers({
+  setEntries(
+    _: RESTHistoryType | GraphqlHistoryType,
+    { entries }: { entries: any[] }
+  ) {
     return {
       state: entries,
     }
   },
-  addEntry(currentVal, { entry }) {
+  addEntry(currentVal: RESTHistoryType | GraphqlHistoryType, { entry }) {
     return {
       state: [entry, ...currentVal.state].slice(0, HISTORY_LIMIT),
     }
   },
-  deleteEntry(currentVal, { entry }) {
+  deleteEntry(currentVal: RESTHistoryType | GraphqlHistoryType, { entry }) {
     return {
       state: currentVal.state.filter((e) => !eq(e, entry)),
     }
@@ -36,7 +39,7 @@ const HistoryDispatcher: Dispatchers<RESTHistoryType | GraphqlHistoryType> = {
       state: [],
     }
   },
-  toggleStar(currentVal, { entry }) {
+  toggleStar(currentVal: RESTHistoryType | GraphqlHistoryType, { entry }) {
     return {
       state: currentVal.state.map((e) => {
         if (eq(e, entry) && e.star !== undefined) {
@@ -49,7 +52,7 @@ const HistoryDispatcher: Dispatchers<RESTHistoryType | GraphqlHistoryType> = {
       }),
     }
   },
-}
+})
 
 export const restHistoryStore = new DispatchingStore(
   defaultRESTHistoryState,
diff --git a/newstore/settings.ts b/newstore/settings.ts
index cc92a3433..2b3536e53 100644
--- a/newstore/settings.ts
+++ b/newstore/settings.ts
@@ -1,8 +1,7 @@
 import { pluck, distinctUntilChanged } from "rxjs/operators"
 import has from "lodash/has"
 import { Observable } from "rxjs"
-import DispatchingStore from "./DispatchingStore"
-import type { Dispatchers } from "./DispatchingStore"
+import DispatchingStore, { defineDispatchers } from "./DispatchingStore"
 import type { KeysMatching } from "~/types/ts-utils"
 
 export const defaultSettings = {
@@ -28,12 +27,15 @@ export type SettingsType = typeof defaultSettings
 
 const validKeys = Object.keys(defaultSettings)
 
-const dispatchers: Dispatchers<SettingsType> = {
-  bulkApplySettings(_currentState, payload: Partial<SettingsType>) {
+const dispatchers = defineDispatchers({
+  bulkApplySettings(
+    _currentState: SettingsType,
+    payload: Partial<SettingsType>
+  ) {
     return payload
   },
   toggleSetting(
-    currentState,
+    currentState: SettingsType,
     { settingKey }: { settingKey: KeysMatching<SettingsType, boolean> }
   ) {
     if (!has(currentState, settingKey)) {
@@ -80,7 +82,7 @@ const dispatchers: Dispatchers<SettingsType> = {
 
     return result
   },
-}
+})
 
 export const settingsStore = new DispatchingStore(defaultSettings, dispatchers)