Handle effects returned from event handlers

src/event.js

@@ -1,4 +1,5 @@
 import { queue } from "./internal/queue";
+import { effect } from "./effect";
 
 /**
  * The event module provides machanisms to trigger and handle the happening of
@@ -28,7 +29,7 @@ export const eventQueue = queue();
  *    and must return a map of effects that should be applied.
  */
 export function handling(eventId, handlerFn) {
-  return rawHandling(eventId, [], context => {
+  return rawHandling(eventId, [effectsInterceptor], context => {
     let [eventId, args] = context.causes.event;
     context.effects = handlerFn(context.causes, eventId, ...args);
     return context;
@@ -97,6 +98,20 @@ export function clearHandlings() {
   registry.clear();
 }
 
+/**
+ * An interceptor which calls the corresponding effect handler for each
+ * described effect in `context.effects`.
+ */
+export function effectsInterceptor(nextFn) {
+  return context => {
+    context = nextFn(context);
+    for (let effectId in context.effects) {
+      effect(effectId, context.effects[effectId]);
+    }
+    return context;
+  };
+}
+
 function handle(eventId, ...args) {
   let handlerFn = registry.get(eventId);
   if (handlerFn) {

src/event.test.js

@@ -6,6 +6,7 @@ import {
   handling,
   rawHandling,
 } from "./event";
+import { clearEffectors, effector } from "./effect";
 
 /* global global */
 
@@ -36,6 +37,7 @@ beforeEach(() => {
   global.console.warn = jest.fn();
   eventQueue.tickFn(ticker.dispatch);
   clearHandlings();
+  clearEffectors();
 });
 
 describe("handling", () => {
@@ -51,6 +53,17 @@ describe("handling", () => {
     expect(context.causes.event).toStrictEqual(["foo", ["bar", "baz"]]);
     expect(context.effects.succeed).toBeTruthy();
   });
+  it("handles effects from context", () => {
+    let succeed = false;
+    let handler = handling("foo", () => ({ bar: "baz" }));
+    effector("bar", arg => {
+      expect(arg).toBe("baz");
+      succeed = true;
+    });
+    expect(succeed).toBeFalsy();
+    handler("foo");
+    expect(succeed).toBeTruthy();
+  });
 });
 
 describe("rawHandling", () => {