feat(injector): add $provide.decorator

1 files changed, 14 insertions, 1 deletions

diff --git a/src/Injector.js b/src/Injector.js
index 8df47306..517e3e00 100644
--- a/src/Injector.js
+++ b/src/Injector.js
@@ -251,7 +251,8 @@ function createInjector(modulesToLoad, moduleRegistry) {
   value('$provide', {
     service: service,
     factory: factory,
-    value: value
+    value: value,
+    decorator: decorator
   });
 
   loadModule(modulesToLoad);
@@ -274,6 +275,18 @@ function createInjector(modulesToLoad, moduleRegistry) {
 
   function value(name, value) { factory(name, valueFn(value)); }
 
+  function decorator(name, decorFn) {
+    var origProvider = cache['#' + name + providerSuffix];
+    if (!origProvider) throw Error("Can't find provider for: " + name);
+    if (cache['#' + name]) throw Error("Service " + name + " already instantiated, can't decorate!");
+    var orig$get = origProvider.$get;
+    origProvider.$get = function() {
+      var origInstance = $injector.invoke(origProvider, orig$get);
+      return $injector.invoke(null, decorFn, {$delegate: origInstance});
+    };
+  }
+
+
   function getService(value) {
     if (typeof value !== 'string') {
       throw Error('Service name expected');