feat(overmind): expose mutation listeners and reaction on context

Author: christianalfoni

packages/node_modules/overmind/src/Overmind.ts

@@ -374,6 +374,9 @@ export class Overmind<ThisConfig extends IConfiguration>
       proxyStateTree: this.proxyStateTreeInstance,
       effects: this.trackEffects(this.effects, execution),
       addNamespace: this.addNamespace.bind(this),
+      reaction: this.reaction.bind(this),
+      addMutationListener: this.addMutationListener.bind(this),
+      addFlushListener: this.addFlushListener.bind(this),
     }
   }
   private addNamespace(

packages/node_modules/overmind/src/operator.ts

@@ -194,6 +194,9 @@ export function createOperator<ThisConfig extends IConfiguration>(
           effects: context.effects,
           actions: context.actions,
           execution: context.execution,
+          addFlushListener: context.addFlushListener,
+          addMutationListener: context.addMutationListener,
+          reaction: context.reaction,
         },
         context.value,
         (err, value, options = {}) => {
@@ -298,6 +301,9 @@ export function createMutationOperator<ThisConfig extends IConfiguration>(
           effects: context.effects,
           actions: context.actions,
           execution: context.execution,
+          addFlushListener: context.addFlushListener,
+          addMutationListener: context.addMutationListener,
+          reaction: context.reaction,
         },
         process.env.NODE_ENV === 'production'
           ? context.value

packages/node_modules/overmind/src/types.ts

@@ -1,5 +1,6 @@
 import { ResolveAction, ContextFunction } from './internalTypes'
 import { IS_OPERATOR } from './utils'
+import { IMutationCallback, IFlushCallback } from 'proxy-state-tree'
 
 /** ===== PUBLIC API
  */
@@ -19,6 +20,9 @@ export type IContext<T extends IConfiguration> = {
   state: T['state']
   actions: { [K in keyof T['actions']]: ResolveAction<T['actions'][K]> }
   effects: T['effects']
+  reaction: IReaction<{ state: T['state'] }>
+  addMutationListener: (cb: IMutationCallback) => () => void
+  addFlushListener: (cb: IFlushCallback) => () => void
 }
 
 export interface IAction<I, O> extends ContextFunction<I, O> {}
@@ -27,7 +31,7 @@ export interface IOperator<I, O> extends ContextFunction<I, O> {
   [IS_OPERATOR]: true
 }
 
-export interface IReaction<T extends IContext<any>> {
+export interface IReaction<T extends { state?: IState }> {
   <O>(
     stateCallback: (state: T['state']) => O,
     updateCallback: (value: O) => void,