fix($inject): enhance annotate function to work with inheritance

src/auto/injector.js

@@ -96,8 +96,9 @@ function annotate(fn, strictDi, name) {
       last;
 
   if (typeof fn === 'function') {
-    if (!($inject = fn.$inject)) {
-      $inject = [];
+    $inject = fn.$inject;
+    if (!$inject || !fn.hasOwnProperty('$inject')) {
+      var $computedInject = [];
       if (fn.length) {
         if (strictDi) {
           if (!isString(name) || !name) {
@@ -109,10 +110,17 @@ function annotate(fn, strictDi, name) {
         argDecl = extractArgs(fn);
         forEach(argDecl[1].split(FN_ARG_SPLIT), function(arg) {
           arg.replace(FN_ARG, function(all, underscore, name) {
-            $inject.push(name);
+            $computedInject.push(name);
           });
         });
       }
+
+      var proto = fn.prototype && Object.getPrototypeOf(fn.prototype);
+      if (!$computedInject.length && !$inject && proto && proto.constructor) {
+        $inject = annotate(proto.constructor, strictDi, name);
+      } else {
+        $inject = $computedInject.length ? $computedInject : ($inject || []);
+      }
       fn.$inject = $inject;
     }
   } else if (isArray(fn)) {

test/auto/injectorSpec.js

@@ -440,6 +440,45 @@ describe('injector', function() {
     });
 
 
+    it('should handle inheritance without own args', function() {
+      function Base(a) {
+      }
+      function Sub() {
+        Base.apply(this, arguments);
+      }
+      Sub.prototype = Object.create(Base.prototype);
+      Sub.prototype.constructor = Sub;
+
+      expect(annotate(Base)).toEqual(['a']);
+      expect(annotate(Sub)).toEqual(['a']);
+
+      delete Base.$inject;
+      delete Sub.$inject;
+
+      expect(annotate(Sub)).toEqual(['a']);
+      expect(annotate(Base)).toEqual(['a']);
+    });
+
+    it('should handle inheritance with different args', function() {
+      function Base(a) {
+      }
+      function Sub(x, a) {
+        Base.call(this, a);
+      }
+      Sub.prototype = Object.create(Base.prototype);
+      Sub.prototype.constructor = Sub;
+
+      expect(annotate(Base)).toEqual(['a']);
+      expect(annotate(Sub)).toEqual(['x', 'a']);
+
+      delete Base.$inject;
+      delete Sub.$inject;
+
+      expect(annotate(Sub)).toEqual(['x', 'a']);
+      expect(annotate(Base)).toEqual(['a']);
+    });
+
+
     describe('es6', function() {
       if (support.shorthandMethods) {
         // The functions are generated using `eval` as just having the ES6 syntax can break some browsers.
@@ -501,6 +540,38 @@ describe('injector', function() {
 
           expect(instance).toEqual(jasmine.any(Clazz));
         });
+
+        it('should annotate correctly when inheriting with different constructor args', function() {
+          // eslint-disable-next-line no-eval
+          var clazzes = eval('(() => { class Base { constructor(a) {} }; class Sub extends Base { constructor(x, a) {super(a);} }; return {Base,Sub}})()');
+          var Base = clazzes.Base;
+          var Sub = clazzes.Sub;
+
+          expect(annotate(Base)).toEqual(['a']);
+          expect(annotate(Sub)).toEqual(['x', 'a']);
+
+          delete Base.$inject;
+          delete Sub.$inject;
+
+          expect(annotate(Sub)).toEqual(['x', 'a']);
+          expect(annotate(Base)).toEqual(['a']);
+        });
+
+        it('should annotate correctly when inheriting without subclass constructor', function() {
+          // eslint-disable-next-line no-eval
+          var clazzes = eval('(() => { class Base { constructor(a) {} }; class Sub extends Base {}; return {Base,Sub}})()');
+          var Base = clazzes.Base;
+          var Sub = clazzes.Sub;
+
+          expect(annotate(Base)).toEqual(['a']);
+          expect(annotate(Sub)).toEqual(['a']);
+
+          delete Base.$inject;
+          delete Sub.$inject;
+
+          expect(annotate(Sub)).toEqual(['a']);
+          expect(annotate(Base)).toEqual(['a']);
+        });
       }
     });