WIP: Async mutate idea, not tests

src/index.ts

@@ -1,5 +1,6 @@
 import { ProxyCache } from "./proxy-cache"
 import { addSelectorToTree, getRefDescedents, removeSelectorFromTree, SelectorTreeBranch } from "./selector-map"
+import { isPromise } from "./utils/isPromise"
 
 export type ObjectTree = object
 
@@ -299,9 +300,9 @@ export class MutationsManager {
     return combinedPatches
   }
 
-  mutate <T extends ObjectTree>(
+  mutate <T extends ObjectTree, K extends (mutable: T) => unknown>(
     target: T,
-    callback: (mutable: T) => unknown
+    callback: K
   ) {
     const isOuterMostTransactionForThisObject = !this.hasRoot(target)
     if ( isOuterMostTransactionForThisObject ) {
@@ -313,7 +314,18 @@ export class MutationsManager {
       return
     }
 
-    callback(proxyWrapper)
+    const result = callback(proxyWrapper)
+
+    if ( isPromise(result) ) {
+      return result.then(() => {
+         // only return the patches on the top most level
+          if ( isOuterMostTransactionForThisObject ) {
+            return this.commit(target)
+          }
+
+          return []
+      })
+    }
 
     // only return the patches on the top most level
     if ( isOuterMostTransactionForThisObject ) {
@@ -326,9 +338,9 @@ export class MutationsManager {
 
 const mutationsManager = new MutationsManager()
 
-export const mutate = <T extends ObjectTree>(
+export const mutate = <T extends ObjectTree, K extends (mutable: T) => unknown>(
   stateTree: T,
-  callback: (mutable: T) => unknown
+  callback: K
 ) => {
   return mutationsManager.mutate(stateTree, callback)
 }

src/utils/isPromise.ts

@@ -0,0 +1,8 @@
+export function isPromise(p: any): p is Promise<unknown> {
+    return (
+        p !== null &&
+        typeof p === 'object' &&
+        typeof p.then === 'function' &&
+        typeof p.catch === 'function'
+    )
+}

tests/nested-mutate.test.ts

@@ -6,8 +6,8 @@ describe('nested mutate calls', () => {
   it('generates correct patches on each nested mutate call for the same object', () => {
     const state: Record<string, string> = {}
 
-    let innerPatches1: JSONPatchEnhanced[] = []
-    let innerPatches2: JSONPatchEnhanced[] = []
+    let innerPatches1: JSONPatchEnhanced[] | Promise<JSONPatchEnhanced[]> = []
+    let innerPatches2: JSONPatchEnhanced[] | Promise<JSONPatchEnhanced[]> = []
 
     const outerPatch = mutate(state, (modifiable) => {
       modifiable.changedTopLevelMutate = 'changed'
@@ -33,8 +33,8 @@ describe('nested mutate calls', () => {
     const state1: Record<string, string> = {}
     const state2: Record<string, string> = {}
 
-    let outerPatchState2: JSONPatchEnhanced[] = []
-    let innerPatchState1: JSONPatchEnhanced[] = []
+    let outerPatchState2: JSONPatchEnhanced[] | Promise<JSONPatchEnhanced[]> = []
+    let innerPatchState1: JSONPatchEnhanced[] | Promise<JSONPatchEnhanced[]> = []
 
     const outerPatchState1 = mutate(state1, (modifiable) => {
       modifiable.changedTopLevelMutate = 'changed'

tests/tasklistapp.test.ts

@@ -222,12 +222,12 @@ describe('Task List project test suite', () => {
   })
 
 
-  it('creates json patch for task add, update, remove', () => {
+  it('creates json patch for task add, update, remove', async () => {
     const clientTaskList = new TaskListProject() // client
     const serverTaskList = new TaskListProject() // server
 
     // ui click -> bla bla bla -> action to add task
-    const clientPatchArray = mutate(clientTaskList, (mutateTaskList) => {
+    const clientPatchArray = await mutate(clientTaskList, (mutateTaskList) => {
       mutateTaskList.createTask('test task')
     })
 
@@ -243,7 +243,7 @@ describe('Task List project test suite', () => {
 
 
     const NEW_TASK_TITLE = 'renamed task title'
-    const jsonPatchForModificationOfTask = mutate(clientTaskList, (mutateTaskList) => {
+    const jsonPatchForModificationOfTask = await mutate(clientTaskList, (mutateTaskList) => {
       const targetTask = mutateTaskList.tasks[idOfCreatedTask]
       targetTask!.title = NEW_TASK_TITLE
       targetTask!.checked = true
@@ -254,7 +254,7 @@ describe('Task List project test suite', () => {
     expect(serverTaskList.tasks[idOfCreatedTask]).toHaveProperty('checked', true)
     expect(serverTaskList.tasks[idOfCreatedTask]).toHaveProperty('title', NEW_TASK_TITLE)
 
-    const jsonPatchForDelete = mutate(clientTaskList, (mutateTaskList) => {
+    const jsonPatchForDelete = await mutate(clientTaskList, (mutateTaskList) => {
       mutateTaskList.removeTaskById(idOfCreatedTask)
     })