fix(subscriberCollection): handle cascading calls

Fixes #252, Fixes jdanyow/aurelia-computed#12

Handles scenarios where observers have subscriptions that overflow into the 'rest' buckets and calling one observer's subscribers causes another observer's subscribers to be called

src/subscriber-collection.js

@@ -53,8 +53,9 @@ function removeSubscriber(context, callable) {
   return true;
 }
 
-let tempContextsRest = [null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null];
-let tempCallablesRest = [null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null];
+let arrayPool1 = [];
+let arrayPool2 = [];
+let poolUtilization = [];
 
 function callSubscribers(newValue, oldValue) {
   let context0 = this._context0;
@@ -63,12 +64,32 @@ function callSubscribers(newValue, oldValue) {
   let callable1 = this._callable1;
   let context2 = this._context2;
   let callable2 = this._callable2;
-  let length = !this._contextsRest ? 0 : this._contextsRest.length;
-  let i = length;
+  let length = this._contextsRest ? this._contextsRest.length : 0;
+  let contextsRest;
+  let callablesRest;
+  let poolIndex;
+  let i;
   if (length) {
+    // grab temp arrays from the pool.
+    poolIndex = poolUtilization.length;
+    while (poolIndex-- && poolUtilization[poolIndex]) { }
+    if (poolIndex < 0) {
+      poolIndex = poolUtilization.length;
+      contextsRest = [];
+      callablesRest = [];
+      poolUtilization.push(true);
+      arrayPool1.push(contextsRest);
+      arrayPool2.push(callablesRest);
+    } else {
+      poolUtilization[poolIndex] = true;
+      contextsRest = arrayPool1[poolIndex];
+      callablesRest = arrayPool2[poolIndex];
+    }
+    // copy the contents of the "rest" arrays.
+    i = length;
     while(i--) {
-      tempContextsRest[i] = this._contextsRest[i];
-      tempCallablesRest[i] = this._callablesRest[i];
+      contextsRest[i] = this._contextsRest[i];
+      callablesRest[i] = this._callablesRest[i];
     }
   }
 
@@ -93,16 +114,19 @@ function callSubscribers(newValue, oldValue) {
       context2(newValue, oldValue);
     }
   }
-  for (i = 0; i < length; i++) {
-    let callable = tempCallablesRest[i];
-    let context = tempContextsRest[i]
-    if (callable) {
-      callable.call(context, newValue, oldValue);
-    } else {
-      context(newValue, oldValue);
+  if (length) {
+    for (i = 0; i < length; i++) {
+      let callable = callablesRest[i];
+      let context = contextsRest[i]
+      if (callable) {
+        callable.call(context, newValue, oldValue);
+      } else {
+        context(newValue, oldValue);
+      }
+      contextsRest[i] = null;
+      callablesRest[i] = null;
     }
-    tempContextsRest[i] = null;
-    tempCallablesRest[i] = null;
+    poolUtilization[poolIndex] = false;
   }
 }
 

test/subscriber-collection.spec.js

@@ -0,0 +1,46 @@
+import {subscriberCollection} from '../src/subscriber-collection';
+
+@subscriberCollection()
+class Test { }
+
+describe('subscriberCollection', () => {
+  it('calls subscribers', () => {
+    let observer = new Test();
+    let observer2 = new Test();
+
+    let callable1 = { call: jasmine.createSpy('call') };
+    observer.addSubscriber('1', callable1);
+    let callable2 = { call: jasmine.createSpy('call') };
+    observer.addSubscriber('2', callable2);
+    let callable3 = { call: jasmine.createSpy('call') };
+    observer.addSubscriber('3', callable3);
+    let callable4 = { call: jasmine.createSpy('call').and.callFake(() => observer2.callSubscribers('new value2', 'old value2')) };
+    observer.addSubscriber('4', callable4);
+    let callable5 = { call: jasmine.createSpy('call') };
+    observer.addSubscriber('5', callable5);
+
+    let callable6 = { call: jasmine.createSpy('call') };
+    observer2.addSubscriber('6', callable6);
+    let callable7 = { call: jasmine.createSpy('call') };
+    observer2.addSubscriber('7', callable7);
+    let callable8 = { call: jasmine.createSpy('call') };
+    observer2.addSubscriber('8', callable8);
+    let callable9 = { call: jasmine.createSpy('call') };
+    observer2.addSubscriber('9', callable9);
+    let callable10 = { call: jasmine.createSpy('call') };
+    observer2.addSubscriber('10', callable10);
+
+    observer.callSubscribers('new value', 'old value');
+
+    expect(callable1.call).toHaveBeenCalledWith('1', 'new value', 'old value');
+    expect(callable2.call).toHaveBeenCalledWith('2', 'new value', 'old value');
+    expect(callable3.call).toHaveBeenCalledWith('3', 'new value', 'old value');
+    expect(callable4.call).toHaveBeenCalledWith('4', 'new value', 'old value');
+    expect(callable5.call).toHaveBeenCalledWith('5', 'new value', 'old value');
+    expect(callable6.call).toHaveBeenCalledWith('6', 'new value2', 'old value2');
+    expect(callable7.call).toHaveBeenCalledWith('7', 'new value2', 'old value2');
+    expect(callable8.call).toHaveBeenCalledWith('8', 'new value2', 'old value2');
+    expect(callable9.call).toHaveBeenCalledWith('9', 'new value2', 'old value2');
+    expect(callable10.call).toHaveBeenCalledWith('10', 'new value2', 'old value2');
+  });
+});