feat(injector): handle in-progress async construction

modules/di/src/injector.js

@@ -6,7 +6,16 @@ import {Type, isPresent, isBlank} from 'facade/lang';
 import {Future, FutureWrapper} from 'facade/async';
 import {Key} from './key';
 
-var _creating = new Object();
+class _InProgress {
+  constructor(future:Future) {
+    this.future = future;
+  }
+}
+var _isInProgressSync = new _InProgress(null);
+function _isInProgress(obj) {
+  return obj instanceof _InProgress;
+}
+
 
 export class Injector {
   constructor(bindings:List) {
@@ -14,16 +23,9 @@ export class Injector {
     this._bindings = this._createListOfBindings(flatten);
     this._instances = this._createInstances();
     this._parent = null; //TODO: vsavkin make a parameter
-  }
 
-  _createListOfBindings(flattenBindings):List {
+    this._asyncStrategy = new _AsyncInjectorStrategy(this);
-    var bindings = ListWrapper.createFixedSize(Key.numberOfKeys() + 1);
+    this._syncStrategy = new _SyncInjectorStrategy(this);
-    MapWrapper.forEach(flattenBindings, (keyId, v) => bindings[keyId] = v);
-    return bindings;
-  }
-
-  _createInstances():List {
-    return ListWrapper.createFixedSize(Key.numberOfKeys() + 1);
   }
 
   get(token) {
@@ -42,86 +44,164 @@ export class Injector {
     return this._getByKey(key, true);
   }
 
-  _getByKey(key:Key, returnFuture) {
-    var keyId = key.id;
-    if (key.token === Injector) return this._injector(returnFuture);
-
-    var instance = this._get(this._instances, keyId);
-    if (instance === _creating) {
-      throw new CyclicDependencyError(key);
-    }
-    if (isPresent(instance)) return instance;
-
-    var binding = this._get(this._bindings, keyId);
-    if (isPresent(binding)) {
-      return this._instantiate(key, binding, returnFuture);
-    }
-    if (isPresent(this._parent)) {
-      return this._parent._getByKey(key, returnFuture);
-    }
-
-    throw new NoProviderError(key);
-  }
-
   createChild(bindings:List):Injector {
     var inj = new Injector(bindings);
     inj._parent = this; //TODO: vsavkin: change it when optional parameters are working
     return inj;
   }
 
-  _injector(returnFuture){
+
-    return returnFuture ? FutureWrapper.value(this) : this;
+  _createListOfBindings(flattenBindings):List {
+    var bindings = ListWrapper.createFixedSize(Key.numberOfKeys() + 1);
+    MapWrapper.forEach(flattenBindings, (keyId, v) => bindings[keyId] = v);
+    return bindings;
   }
 
-  _get(list:List, index){
+  _createInstances():List {
-    if (list.length <= index) return null;
+    return ListWrapper.createFixedSize(Key.numberOfKeys() + 1);
-    return ListWrapper.get(list, index);
   }
 
-  _instantiate(key:Key, binding:Binding, returnFuture) {
+  _getByKey(key:Key, returnFuture) {
-    ListWrapper.set(this._instances, key.id, _creating);
+    var strategy = returnFuture ? this._asyncStrategy : this._syncStrategy;
 
-    if (binding.providedAsFuture && !returnFuture) {
+    var instance = strategy.readFromCache(key);
-      throw new AsyncBindingError(key);
+    if (isPresent(instance)) return instance;
+
+    instance = strategy.instantiate(key);
+    if (isPresent(instance)) return instance;
+
+    if (isPresent(this._parent)) {
+      return this._parent._getByKey(key, returnFuture);
+    }
+    throw new NoProviderError(key);
+  }
+
+  _getInstance(key:Key){
+    if (this._instances.length <= key.id) return null;
+    return ListWrapper.get(this._instances, key.id);
+  }
+
+  _setInstance(key:Key, obj){
+    ListWrapper.set(this._instances, key.id, obj);
+  }
+
+  _getBinding(key:Key){
+    if (this._bindings.length <= key.id) return null;
+    return ListWrapper.get(this._bindings, key.id);
+  }
+}
+
+
+class _SyncInjectorStrategy {
+  constructor(injector:Injector) {
+    this.injector = injector;
+  }
+
+  readFromCache(key:Key) {
+    if (key.token === Injector) {
+      return this.injector;
     }
 
-    if (returnFuture) {
+    var instance = this.injector._getInstance(key);
-      return this._instantiateAsync(key, binding);
+
+    // skip async in-progress
+    if (instance === _isInProgressSync) {
+      throw new CyclicDependencyError(key);
+    } else if (isPresent(instance) && !_isInProgress(instance)) {
+      return instance;
     } else {
-      return this._instantiateSync(key, binding);
+      return null;
     }
   }
 
-  _instantiateSync(key:Key, binding:Binding) {
+  instantiate(key:Key) {
-    var deps;
+    var binding = this.injector._getBinding(key);
+    if (isBlank(binding)) return null;
+
+    if (binding.providedAsFuture) throw new AsyncBindingError(key);
+
+    //add a marker so we can detect cyclic dependencies
+    this.injector._setInstance(key, _isInProgressSync);
+
+    var deps = this._resolveDependencies(key, binding);
+    return this._createInstance(key, binding, deps);
+  }
+
+  _resolveDependencies(key:Key, binding:Binding) {
     try {
-      deps = ListWrapper.map(binding.dependencies, d => this._getByKey(d.key, d.asFuture));
+      var getDependency = d => this.injector._getByKey(d.key, d.asFuture);
+      return ListWrapper.map(binding.dependencies, getDependency);
     } catch (e) {
       if (e instanceof ProviderError) e.addKey(key);
       throw e;
     }
+  }
 
+  _createInstance(key:Key, binding:Binding, deps:List) {
     try {
       var instance = binding.factory(deps);
-      ListWrapper.set(this._instances, key.id, instance);
+      this.injector._setInstance(key, instance);
       return instance;
     } catch (e) {
       throw new InstantiationError(e, key);
     }
   }
+}
 
-  _instantiateAsync(key:Key, binding:Binding):Future {
+
-    var instances = this._createInstances();
+
-    var futures = ListWrapper.map(binding.dependencies, d => this._getByKey(d.key, true));
+class _AsyncInjectorStrategy {
-    return FutureWrapper.wait(futures).
+  constructor(injector:Injector) {
-      then(binding.factory).
+    this.injector = injector;
-      then(function(instance) {
+  }
-        ListWrapper.set(instances, key.id, instance);
+
-        return instance
+  readFromCache(key:Key) {
-      });
+    if (key.token === Injector) {
+      return FutureWrapper.value(this.injector);
+    }
+
+    var instance = this.injector._getInstance(key);
+    if (_isInProgress(instance)) {
+      return instance.future;
+    } else if (isPresent(instance)) {
+      return FutureWrapper.value(instance);
+    } else {
+      return null;
+    }
+  }
+
+  instantiate(key:Key) {
+    var binding = this.injector._getBinding(key);
+    if (isBlank(binding)) return null;
+
+    var deps = this._resolveDependencies(key, binding);
+    var future = FutureWrapper.wait(deps).
+      then(deps => this._findOrCreate(key, binding, deps)).
+      then(instance => this._cacheInstance(key, instance));
+
+    this.injector._setInstance(key, new _InProgress(future));
+    return future;
+  }
+
+  _resolveDependencies(key:Key, binding:Binding):List {
+    var getDependency = d => this.injector._getByKey(d.key, true);
+    return ListWrapper.map(binding.dependencies, getDependency);
+  }
+
+  _findOrCreate(key:Key, binding: Binding, deps:List) {
+    var instance = this.injector._getInstance(key);
+    if (! _isInProgress(instance)) return instance;
+    return binding.factory(deps);
+  }
+
+  _cacheInstance(key, instance) {
+    this.injector._setInstance(key, instance);
+    return instance
   }
 }
 
+
+
 function _flattenBindings(bindings:List) {
   var res = {};
   ListWrapper.forEach(bindings, function (b){

modules/di/test/di/async_spec.js

@@ -61,6 +61,45 @@ export function main () {
           done();
         });
       });
+
+      it("should return a future when the binding is sync from cache", function () {
+        var injector = new Injector([
+          UserList
+        ]);
+        expect(injector.get(UserList)).toBeAnInstanceOf(UserList);
+        expect(injector.asyncGet(UserList)).toBeFuture();
+      });
+
+      it("should create only one instance (async + async)", function (done) {
+        var injector = new Injector([
+          bind(UserList).toAsyncFactory([], fetchUsers)
+        ]);
+
+        var ul1 = injector.asyncGet(UserList);
+        var ul2 = injector.asyncGet(UserList);
+
+        FutureWrapper.wait([ul1, ul2]).then(function (uls) {
+          expect(uls[0]).toBe(uls[1]);
+          done();
+        });
+      });
+
+      it("should create only one instance (sync + async)", function (done) {
+        var injector = new Injector([
+          UserList
+        ]);
+
+        var future = injector.asyncGet(UserList);
+        var ul = injector.get(UserList);
+
+        expect(future).toBeFuture();
+        expect(ul).toBeAnInstanceOf(UserList);
+
+        future.then(function (ful) {
+          expect(ful).toBe(ul);
+          done();
+        });
+      });
     });
 
     describe("get", function () {
@@ -105,13 +144,5 @@ export function main () {
         expect(controller.userList).toBeFuture();
       });
     });
-
-
-    // InjectFuture toFactory([@AsyncInject(UserList)], (userListFuutre)]
-    // InjectFuture toFactory((@AsyncInject(UsrList) userListFuutre) => ]
-
-    // resolve exceptions and async
-    // do not construct two instances of the same async dependency if there is one in progress
-    // cycles
   });
 }