feat(inheritence): allow injection w/ inheritence

src/container.js

@@ -415,12 +415,25 @@ export class Container {
   _createInvocationHandler(fn: Function): InvocationHandler {
     let dependencies;
 
-    if (typeof fn.inject === 'function') {
-      dependencies = fn.inject();
-    } else if (fn.inject === undefined) {
+    if (fn.inject === undefined) {
       dependencies = metadata.getOwn(metadata.paramTypes, fn) || _emptyParameters;
     } else {
-      dependencies = fn.inject;
+      function getDependencies(f) {
+        if (!f.hasOwnProperty('inject')) {
+          return [];
+        }
+        if (typeof f.inject === 'function') {
+          return f.inject();
+        } else {
+          return f.inject;
+        }
+      }
+      dependencies = [];
+      let ctor = fn;
+      while (typeof ctor === 'function') {
+        dependencies.push(...getDependencies(ctor));
+        ctor = Object.getPrototypeOf(ctor);
+      }
     }
 
     let invoker = metadata.getOwn(metadata.invoker, fn)

test/container.spec.js

@@ -49,6 +49,69 @@ describe('container', () => {
     });
   });
 
+  describe('inheritence', function() {
+    class Logger {}
+    class Service {}
+
+    it('loads dependencies for the parent class', function() {
+      class ParentApp {
+        static inject() { return [Logger]; }
+        constructor(logger) {
+          this.logger = logger;
+        }
+      }
+
+      class ChildApp extends ParentApp {
+        constructor(...rest) {
+          super(...rest);
+        }
+      }
+
+      let container = new Container();
+      let app = container.get(ChildApp);
+      expect(app.logger).toEqual(jasmine.any(Logger));
+    });
+
+    it('loads dependencies for the child class', function() {
+      class ParentApp {
+      }
+
+      class ChildApp extends ParentApp {
+        static inject() { return [Service]; }
+        constructor(service, ...rest) {
+          super(...rest);
+          this.service = service;
+        }
+      }
+
+      let container = new Container();
+      let app = container.get(ChildApp);
+      expect(app.service).toEqual(jasmine.any(Service));
+    });
+
+    it('loads dependencies for both classes', function() {
+      class ParentApp {
+        static inject() { return [Logger]; }
+        constructor(logger) {
+          this.logger = logger;
+        }
+      }
+
+      class ChildApp extends ParentApp {
+        static inject() { return [Service]; }
+        constructor(service, ...rest) {
+          super(...rest);
+          this.service = service;
+        }
+      }
+
+      let container = new Container();
+      let app = container.get(ChildApp);
+      expect(app.service).toEqual(jasmine.any(Service));
+      expect(app.logger).toEqual(jasmine.any(Logger));
+    });
+  });
+
   describe('registration', () => {
     it('asserts keys are defined', () => {
       let container = new Container();