feat(overmind): add fork operator

Author: christianalfoni

packages/node_modules/overmind/src/createActionFactory.ts

@@ -13,6 +13,12 @@ type OperatorCallback<Context, Value, NewValue = Value> = (
 ) => NewValue | Promise<NewValue>
 
 interface Operators<State, Context, InitialValue, Value> {
+  fork<Paths>(
+    cb: (value: Value, context: Context) => keyof Paths,
+    paths: Paths
+  ): InitialValue extends void
+    ? NoValueAction<State, Context, InitialValue, Value>
+    : Action<State, Context, InitialValue, Value>
   mutation(
     cb: (value: Value, state: State) => any
   ): InitialValue extends void
@@ -99,6 +105,27 @@ export default function createActionFactory<State, Context>(proxyStateTree) {
         runOperators
       ) as any,
       {
+        fork<Paths>(
+          cb: (value: Value, context: Context) => keyof Paths,
+          paths: Paths
+        ) {
+          const operator = (value, context) => {
+            const path = cb(value, context)
+
+            return (paths[path] as any).map(() => value)(value, context, path)
+          }
+          const [
+            chain,
+            initialActionId,
+            runOperators,
+          ] = this.createOperatorResult('fork', cb.name, operator)
+
+          return actionFactory<InitialValue, Value>(
+            chain,
+            initialActionId,
+            runOperators
+          )
+        },
         mutation(cb: (value: Value, state: State) => any) {
           const operator = (value, context) => {
             proxyStateTree.startMutationTracking()
@@ -116,7 +143,7 @@ export default function createActionFactory<State, Context>(proxyStateTree) {
             runOperators,
           ] = this.createOperatorResult('mutation', cb.name, operator)
 
-          return actionFactory<InitialValue>(
+          return actionFactory<InitialValue, Value>(
             chain,
             initialActionId,
             runOperators

packages/node_modules/overmind/src/index.test.ts

@@ -48,6 +48,25 @@ describe('Overmind', () => {
 })
 
 describe('OPERATORS', () => {
+  test('fork', () => {
+    expect.assertions(2)
+    let calledFoo = false
+    const app = new App({
+      state: {},
+      actions: (action) => {
+        return {
+          doThis: action().fork(() => 'foo', {
+            foo: action()
+              .do(() => (calledFoo = true))
+              .map(() => '123'),
+            bar: action().map(() => 123),
+          }),
+        }
+      },
+    })
+    expect(app.actions.doThis()).toBe(undefined)
+    expect(calledFoo).toBe(true)
+  })
   test('mutate', () => {
     const app = new App({
       state: {

packages/node_modules/overmind/src/views/react.ts

@@ -50,7 +50,12 @@ export default class ReactApp<
 
     if (isClassComponent) {
       const originalRender = Component.prototype.render
+      const originalWillUnmount = Component.prototype.componentWillUnmount
 
+      Component.prototype.componentWillUnmount = function() {
+        this.__mutationListener && this.__mutationListener.dispose()
+        originalWillUnmount && originalWillUnmount.call(this)
+      }
       Component.prototype.render = function() {
         const trackId = instance.trackState()
         const value = originalRender.call(this)
@@ -88,6 +93,9 @@ export default class ReactApp<
       >
     > {
       __mutationListener: any
+      componentWillUnmount() {
+        this.__mutationListener && this.__mutationListener.dispose()
+      }
       renderStatelessComponent() {
         const trackId = instance.trackState()
         const value = (Component as any)(