feat(injector): Service look up failures include dependency path

Author: mhevery

src/Injector.js

@@ -44,22 +44,25 @@ function createInjector(factories) {
   });
   return injector;
 
-  function injector(value){
-    if (!(value in instanceCache)) {
-      var factory = factories[value];
-      if (!factory) throw Error("Unknown provider for '" + value + "'.");
+  function injector(serviceId, path){
+    if (!(serviceId in instanceCache)) {
+      var factory = factories[serviceId];
+      path = path || [];
+      path.unshift(serviceId);
+      if (!factory) throw Error("Unknown provider for '" + path.join("' <- '") + "'.");
       inferInjectionArgs(factory);
-      instanceCache[value] = invoke(null, factory);
+      instanceCache[serviceId] = invoke(null, factory, [], path);
+      path.shift();
     }
-    return instanceCache[value];
+    return instanceCache[serviceId];
   }
 
-  function invoke(self, fn, args){
+  function invoke(self, fn, args, path){
     args = args || [];
     var injectNames = fn.$inject || [];
     var i = injectNames.length;
     while(i--) {
-      args.unshift(injector(injectNames[i]));
+      args.unshift(injector(injectNames[i], path));
     }
     return fn.apply(self, args);
   }

test/InjectorSpec.js

@@ -62,12 +62,18 @@ describe('injector', function() {
   });
 
 
-  it('should provide usefull message if no provider', function() {
+  it('should provide useful message if no provider', function() {
     expect(function() {
       injector('idontexist');
     }).toThrow("Unknown provider for 'idontexist'.");
   });
 
+  it('should proved path to the missing provider', function(){
+    expect(function() {
+      injector('idontexist', ['a', 'b']);
+    }).toThrow("Unknown provider for 'idontexist' <- 'a' <- 'b'.");
+  });
+
   it('should autostart eager services', function() {
     var log = '';
     providers('eager', function() {log += 'eager;'; return 'foo';}, {$eager: true});