Allow returning undefined from MutationAction to skip calling the…

… mutation
championswimmer · Jan 2, 2021 · 0aeef04 · 0aeef04
1 parent 08249c5
commit 0aeef04
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Showing 3 changed files with 27 additions and 4 deletions.
diff --git a/docs/pages/core/mutationactions.md b/docs/pages/core/mutationactions.md
@@ -58,4 +58,9 @@ Note that if **S** denotes the type of _state_, then the object returned from a
 `MutationAction` function must of type **Partial\<S\>** 
 The keys present inside the return value (for eg, here `posts`) are replaced into
 the store. 
-:::
+:::
+
+:::tip NOTE
+When a `MutationAction` function returns `undefined`, the mutation part of the
+`MutationAction` will not be called, and the state will remain the same.
+:::
diff --git a/src/mutationaction.ts b/src/mutationaction.ts
@@ -10,7 +10,7 @@ function mutationActionDecoratorFactory<T extends Object>(params: MutationAction
   return function (
     target: T,
     key: string | symbol,
-    descriptor: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<T>>>
+    descriptor: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<T> | undefined>>
   ) {
     const module = target.constructor as Mod<T, any>
     if (!module.hasOwnProperty('mutations')) {
@@ -27,6 +27,7 @@ function mutationActionDecoratorFactory<T extends Object>(params: MutationAction
     ) {
       try {
         const actionPayload = await mutactFunction.call(context, payload)
+        if (actionPayload === undefined) return
         context.commit(key as string, actionPayload)
       } catch (e) {
         if (params.rawError) {
@@ -88,12 +89,12 @@ export function MutationAction<T>(
 export function MutationAction<T, K, M extends K>(
   paramsOrTarget: MutationActionParams<T> | M,
   key?: string | symbol,
-  descriptor?: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<K>>>
+  descriptor?: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<K> | undefined>>
 ):
   | ((
       target: T,
       key: string | symbol,
-      descriptor: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<T>>>
+      descriptor: TypedPropertyDescriptor<(...args: any[]) => Promise<Partial<T> | undefined>>
     ) => void)
   | void {
   if (!key && !descriptor) {

diff --git a/test/mutationaction.ts b/test/mutationaction.ts
@@ -8,6 +8,7 @@ Vue.use(Vuex)
 @Module
 class MyModule extends VuexModule {
   count: number = 0
+  anotherCount: number = 0
   fruit: string = 'Apple'
   vegetable: string | null = null
 
@@ -17,6 +18,12 @@ class MyModule extends VuexModule {
     return { count: newcount }
   }
 
+  @MutationAction
+  async updateAnotherCountConditionally({ newCount, shouldUpdate }: { newCount: number, shouldUpdate: boolean }) {
+    if (!shouldUpdate) return
+    return { anotherCount: newCount }
+  }
+
   @MutationAction
   async changeVeggie() {
     return {vegetable: 'Carrot'}
@@ -75,4 +82,14 @@ describe('dispatching moduleaction works', () => {
     await store.dispatch('changeFruit', 'Guava')
     expect(store.state.mm.fruit).to.equal('Guava')
   })
+
+  it('should be able to skip update', async function () {
+    expect(store.state.mm.anotherCount).to.equal(0)
+
+    await store.dispatch('updateAnotherCountConditionally', { newCount: 5, shouldUpdate: true })
+    expect(store.state.mm.anotherCount).to.equal(5)
+
+    await store.dispatch('updateAnotherCountConditionally', { newCount: 10, shouldUpdate: false })
+    expect(store.state.mm.anotherCount).to.equal(5)
+  })
 })