feat(overmind): statemachines receives the typed state on entry and exit

Author: christianalfoni

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

@@ -231,4 +231,51 @@ describe('Statemachine', () => {
     overmind.state.reset()
     expect(overmind.state.state).toBe('FOO')
   })
+
+  test('should pass statemachine to transition callback, correctly typed', () => {
+    expect.assertions(3)
+
+    type States = {
+      state: 'FOO'
+      foo: string
+    } | {
+      state: 'BAR'
+      bar: string
+    }
+
+    const state = statemachine<States>({
+      FOO: ['BAR'],
+      BAR: ['FOO']
+      }, {
+        state: 'FOO',
+        foo: 'bar'
+      })
+    
+    const transition: Action = ({ state }) => {
+      state.BAR(() => {
+        state.FOO((current) => {
+          current.foo = 'bar2'
+        })
+      }, (current) => {
+        current.bar = 'baz2'
+      })
+    }
+
+    const config = {
+      state,
+      actions: {
+        transition
+      }
+    } 
+
+    interface Action extends IAction<typeof config, void, void> {}
+
+    const overmind = createOvermind(config)
+    overmind.actions.transition()
+    expect(overmind.state.state).toBe('FOO')
+    // @ts-ignore
+    expect(overmind.state.foo).toBe('bar2')
+    // @ts-ignore
+    expect(overmind.state.bar).toBe('baz2')
+  })
 })

packages/node_modules/overmind/src/statemachine.ts

@@ -1,6 +1,7 @@
-import { IState } from '.'
 import { PROXY_TREE, VALUE } from 'proxy-state-tree'
 
+import { IState } from '.'
+
 type TStates = IState & {
   state: string | number,
 }
@@ -13,7 +14,7 @@ export type Statemachine<States extends TStates> = States & {
   reset: () => void
   whenTransitioned: (state: States["state"]) => Promise<void>
 } & {
-  [State in States["state"]]: <T extends () => any>(entry?: T, exit?: () => void) => T extends () => infer U ? U : void
+  [State in States["state"]]: <O>(entry?:  (current: States extends { state: State } ? States : never) => O, exit?: (current: States extends { state: State } ? States : never) => void) => O
 }
 
 const CURRENT_EXIT = Symbol('CURRENT_EXIT')
@@ -35,10 +36,10 @@ class StateMachine<States extends TStates>  {
           const tree = (this[PROXY_TREE].master.mutationTree || this[PROXY_TREE])
 
           tree.enableMutations()
-          if (this[CURRENT_EXIT]) this[CURRENT_EXIT]()
+          if (this[CURRENT_EXIT]) this[CURRENT_EXIT](this)
           this[VALUE][CURRENT_EXIT] = exit
           this.state = key as any
-          const result = entry && entry()
+          const result = entry && entry(this)
           tree.blockMutations()
 
           if (this[VALUE][PENDING_TRANSITIONS][this.state]) {