feat: impl willReady

Refs: eggjs/egg#2520

appveyor.yml

@@ -11,6 +11,6 @@ install:
 test_script:
   - node --version
   - npm --version
-  - npm run ci
+  - npm run test
 
 build: off

lib/ready.js

@@ -5,6 +5,8 @@ const once = require('once');
 const ready = require('get-ready');
 const uuid = require('uuid');
 const debug = require('debug')('ready-callback');
+const WILL_READY_CALLBACKS = Symbol('willReadyCallbacks');
+const TRIGGER_WILL_READY = Symbol('triggerWillReady');
 
 const defaults = {
   timeout: 10000,
@@ -29,12 +31,13 @@ class Ready extends EventEmitter {
     this.opt = opt || {};
     this.isError = false;
     this.cache = new Map();
+    this[WILL_READY_CALLBACKS] = [];
 
     setImmediate(() => {
       // fire callback directly when no registered ready callback
       if (this.cache.size === 0) {
         debug('Fire callback directly');
-        this.ready(true);
+        this[TRIGGER_WILL_READY]();
       }
     });
   }
@@ -52,6 +55,7 @@ class Ready extends EventEmitter {
     // delegate API to object
     obj.ready = this.ready.bind(this);
     obj.readyCallback = this.readyCallback.bind(this);
+    obj.willReady = this.willReady.bind(this);
 
     // only ready once with error
     this.once('error', err => obj.ready(err));
@@ -121,11 +125,20 @@ class Ready extends EventEmitter {
 
     if (this.cache.size === 0) {
       debug('[%s] Fire callback async', id);
-      this.ready(true);
+      this[TRIGGER_WILL_READY]();
     }
     return this;
   }
 
+  willReady(fn) {
+    this[WILL_READY_CALLBACKS].push(fn);
+  }
+
+  [TRIGGER_WILL_READY]() {
+    return Promise.all(this[WILL_READY_CALLBACKS].map(fn => fn()))
+      .then(() => this.ready(true))
+      .catch(e => this.ready(e));
+  }
 }
 
 // Use ready-callback with options

test/ready.test.js

@@ -462,4 +462,19 @@ describe('Ready', function() {
     assert(ready.obj === obj1);
     assert(ready.obj !== obj2);
   });
+
+  describe('willReady', function() {
+    it('should fire willRead callbacks before ready', function() {
+      const obj = new EventEmitter();
+      const ready = new Ready();
+      ready.mixin(obj);
+      const endA = obj.readyCallback('a');
+      const spyWillReady = spy();
+      obj.willReady(spyWillReady);
+      setTimeout(endA, 1);
+      setTimeout(function() {
+        assert.strictEqual(spyWillReady.callCount, 1);
+      }, 10);
+    });
+  });
 });