From 67a2f254a2957ed721a1b9e6919c9ee9eeb6437e Mon Sep 17 00:00:00 2001
From: Paul Taylor <paul.e.taylor@me.com>
Date: Wed, 10 Feb 2016 14:47:52 -0800
Subject: [PATCH] fix(do): fix do operator to invoke observer message handlers
 in the right context.

---
 spec/operators/do-spec.js | 27 ++++++++++++
 src/operator/do.ts        | 93 +++++++++++++++++----------------------
 2 files changed, 67 insertions(+), 53 deletions(-)

diff --git a/spec/operators/do-spec.js b/spec/operators/do-spec.js
index 5edbeab23f..84e85f6c97 100644
--- a/spec/operators/do-spec.js
+++ b/spec/operators/do-spec.js
@@ -1,5 +1,6 @@
 /* globals describe, it, expect, expectObservable, expectSubscriptions, hot, cold */
 var Rx = require('../../dist/cjs/Rx');
+var Subject = Rx.Subject;
 var Observable = Rx.Observable;
 
 describe('Observable.prototype.do()', function () {
@@ -57,6 +58,32 @@ describe('Observable.prototype.do()', function () {
     expect(results).toEqual(expected);
   });
 
+  it('should handle everything with a Subject', function () {
+    var expected = [1,2,3];
+    var results = [];
+    var completeCalled = false;
+    var subject = new Subject();
+
+    subject.subscribe({
+      next: function (x) {
+        results.push(x);
+      },
+      error: function (err) {
+        throw 'should not be called';
+      },
+      complete: function () {
+        completeCalled = true;
+      }
+    });
+
+    Observable.of(1,2,3)
+      .do(subject)
+      .subscribe();
+
+    expect(completeCalled).toBe(true);
+    expect(results).toEqual(expected);
+  });
+
   it('should handle an error with a callback', function () {
     var errored = false;
     Observable.throw('bad').do(null, function (err) {
diff --git a/src/operator/do.ts b/src/operator/do.ts
index 73e1ac47f4..f06a09c705 100644
--- a/src/operator/do.ts
+++ b/src/operator/do.ts
@@ -1,9 +1,7 @@
 import {Operator} from '../Operator';
-import {Observer} from '../Observer';
 import {Subscriber} from '../Subscriber';
-
-import {noop} from '../util/noop';
 import {Observable} from '../Observable';
+import {PartialObserver} from '../Observer';
 
 /**
  * Returns a mirrored Observable of the source Observable, but modified so that the provided Observer is called
@@ -14,77 +12,66 @@ import {Observable} from '../Observable';
  * @param {function} [complete] callback for the completion of the source.
  * @reurns {Observable} a mirrored Observable with the specified Observer or callback attached for each item.
  */
-export function _do<T>(nextOrObserver?: Observer<T> | ((x: T) => void), error?: (e: any) => void, complete?: () => void): Observable<T> {
-  let next: (x: T) => void;
-  if (nextOrObserver && typeof nextOrObserver === 'object') {
-    next = (<Observer<T>>nextOrObserver).next;
-    error = (<Observer<T>>nextOrObserver).error;
-    complete = (<Observer<T>>nextOrObserver).complete;
-  } else {
-    next = <(x: T) => void>nextOrObserver;
-  }
-  return this.lift(new DoOperator(next || noop, error || noop, complete || noop));
+export function _do<T>(nextOrObserver?: PartialObserver<T> | ((x: T) => void),
+                       error?: (e: any) => void,
+                       complete?: () => void): Observable<T> {
+  return this.lift(new DoOperator(nextOrObserver, error, complete));
 }
 
 class DoOperator<T> implements Operator<T, T> {
-
-  next: (x: T) => void;
-  error: (e: any) => void;
-  complete: () => void;
-
-  constructor(next: (x: T) => void, error: (e: any) => void, complete: () => void) {
-    this.next = next;
-    this.error = error;
-    this.complete = complete;
+  constructor(private nextOrObserver?: PartialObserver<T> | ((x: T) => void),
+              private error?: (e: any) => void,
+              private complete?: () => void) {
   }
-
   call(subscriber: Subscriber<T>): Subscriber<T> {
-    return new DoSubscriber(subscriber, this.next, this.error, this.complete);
+    return new DoSubscriber(subscriber, this.nextOrObserver, this.error, this.complete);
   }
 }
 
 class DoSubscriber<T> extends Subscriber<T> {
 
-  private __next: (x: T) => void;
-  private __error: (e: any) => void;
-  private __complete: () => void;
+  private safeSubscriber: Subscriber<T>;
 
-  constructor(destination: Subscriber<T>, next: (x: T) => void, error: (e: any) => void, complete: () => void) {
+  constructor(destination: Subscriber<T>,
+              nextOrObserver?: PartialObserver<T> | ((x: T) => void),
+              error?: (e: any) => void,
+              complete?: () => void) {
     super(destination);
-    this.__next = next;
-    this.__error = error;
-    this.__complete = complete;
+
+    const safeSubscriber = new Subscriber<T>(nextOrObserver, error, complete);
+    safeSubscriber.syncErrorThrowable = true;
+    this.add(safeSubscriber);
+    this.safeSubscriber = safeSubscriber;
   }
 
-  // NOTE: important, all try catch blocks below are there for performance
-  // reasons. tryCatcher approach does not benefit this operator.
-  protected _next(value: T) {
-    try {
-      this.__next(value);
-    } catch (err) {
-      this.destination.error(err);
-      return;
+  protected _next(value: T): void {
+    const { safeSubscriber } = this;
+    safeSubscriber.next(value);
+    if (safeSubscriber.syncErrorThrown) {
+      this.destination.error(safeSubscriber.syncErrorValue);
+    } else {
+      this.destination.next(value);
     }
-    this.destination.next(value);
   }
 
-  protected _error(err: any) {
-    try {
-      this.__error(err);
-    } catch (err) {
+  protected _error(err: any): void {
+    const { safeSubscriber } = this;
+    safeSubscriber.error(err);
+    if (safeSubscriber.syncErrorThrown) {
+      this.destination.error(safeSubscriber.syncErrorValue);
+    } else {
       this.destination.error(err);
-      return;
     }
-    this.destination.error(err);
   }
 
-  protected _complete() {
-    try {
-      this.__complete();
-    } catch (err) {
-      this.destination.error(err);
-      return;
+  protected _complete(): void {
+    const { safeSubscriber } = this;
+    safeSubscriber.complete();
+    if (safeSubscriber.syncErrorThrown) {
+      this.destination.error(safeSubscriber.syncErrorValue);
+    } else {
+      this.destination.complete();
     }
-    this.destination.complete();
   }
 }
+