fix(SafeSubscriber): SafeSubscriber shouldn't mutate incoming Observers.

2237

Author: trxcllnt

spec/Observable-spec.ts

@@ -476,8 +476,9 @@ describe('Observable', () => {
         ' of the anonymous observer', (done: MochaDone) => {
         //intentionally not using lambda to avoid typescript's this context capture
         const o = {
+          myValue: 'foo',
           next: function next(x) {
-            expect(this).to.equal(o);
+            expect(this.myValue).to.equal('foo');
             expect(x).to.equal(1);
             done();
           }
@@ -490,8 +491,9 @@ describe('Observable', () => {
         ' of the anonymous observer', (done: MochaDone) => {
         //intentionally not using lambda to avoid typescript's this context capture
         const o = {
+          myValue: 'foo',
           error: function error(err) {
-            expect(this).to.equal(o);
+            expect(this.myValue).to.equal('foo');
             expect(err).to.equal('bad');
             done();
           }
@@ -504,8 +506,9 @@ describe('Observable', () => {
         ' context of the anonymous observer', (done: MochaDone) => {
         //intentionally not using lambda to avoid typescript's this context capture
          const o = {
+          myValue: 'foo',
           complete: function complete() {
-            expect(this).to.equal(o);
+            expect(this.myValue).to.equal('foo');
             done();
           }
         };
@@ -527,8 +530,9 @@ describe('Observable', () => {
 
         //intentionally not using lambda to avoid typescript's this context capture
         const o = {
+          myValue: 'foo',
           next: function next(x) {
-            expect(this).to.equal(o);
+            expect(this.myValue).to.equal('foo');
             throw x;
           }
         };

src/Subscriber.ts

@@ -167,14 +167,16 @@ class SafeSubscriber<T> extends Subscriber<T> {
     if (isFunction(observerOrNext)) {
       next = (<((value: T) => void)> observerOrNext);
     } else if (observerOrNext) {
-      context = observerOrNext;
       next = (<PartialObserver<T>> observerOrNext).next;
       error = (<PartialObserver<T>> observerOrNext).error;
       complete = (<PartialObserver<T>> observerOrNext).complete;
-      if (isFunction(context.unsubscribe)) {
-        this.add(<() => void> context.unsubscribe.bind(context));
+      if (observerOrNext !== emptyObserver) {
+        context = Object.create(observerOrNext);
+        if (isFunction(context.unsubscribe)) {
+          this.add(<() => void> context.unsubscribe.bind(context));
+        }
+        context.unsubscribe = this.unsubscribe.bind(this);
       }
-      context.unsubscribe = this.unsubscribe.bind(this);
     }
 
     this._context = context;