fix(take): deal with total <= 0 and add tests

Author: adrianomelo

spec/operators/take-spec.js

@@ -0,0 +1,70 @@
+/* globals describe, it, expect, expectObservable, hot */
+var Rx = require('../../dist/cjs/Rx');
+var Observable = Rx.Observable;
+
+describe('Observable.prototype.take()', function () {
+  it('should work with empty', function () {
+    var e1 = Observable.empty();
+    var expected = '|';
+    expectObservable(e1.take(42)).toBe(expected);
+  });
+
+  it('should go on forever on never', function () {
+    var e1 = Observable.never();
+    var expected = '-';
+    expectObservable(e1.take(42)).toBe(expected);
+  });
+
+  it('should be empty on take(0)', function () {
+    var e1 = hot('--a--^--b----c---d--|');
+    var expected = '|';
+    expectObservable(e1.take(0)).toBe(expected);
+  });
+
+  it('should take one value of an observable with one value', function () {
+    var e1 =   hot('---(a|)');
+    var expected = '---(a|)';
+    expectObservable(e1.take(1)).toBe(expected);
+  });
+
+  it('should take one values of an observable with many values', function () {
+    var e1 = hot('--a--^--b----c---d--|');
+    var expected =    '---(b|)';
+    expectObservable(e1.take(1)).toBe(expected);
+  });
+
+  it('should take two values of an observable with many values', function () {
+    var e1 = hot('--a--^--b----c---d--|');
+    var expected =    '---b----(c|)';
+    expectObservable(e1.take(2)).toBe(expected);
+  });
+
+  it('should error on empty', function () {
+    var e1 = hot('--a--^----|');
+    var expected =    '-----|';
+    expectObservable(e1.take(42)).toBe(expected);
+  });
+
+  it('should propagate error from the source observable', function () {
+    var e1 = hot('---^---#', null, 'too bad');
+    var expected =  '----#';
+    expectObservable(e1.take(42)).toBe(expected, null, 'too bad');
+  });
+
+  it('should propagate error from an observable with values', function () {
+    var e1 = hot('---^--a--b--#');
+    var expected =  '---a--b--#';
+    expectObservable(e1.take(42)).toBe(expected);
+  });
+
+  it('should work with throw', function () {
+    var e1 = Observable.throw(new Error('too bad'));
+    var expected = '#';
+    expectObservable(e1.take(42)).toBe(expected, null, new Error('too bad'));
+  });
+
+  it('should throw if total is less than zero', function () {
+    expect(function () { Observable.range(0,10).take(-1); })
+      .toThrow(new Rx.ArgumentOutOfRangeError());
+  });
+});

src/operators/take.ts

@@ -1,12 +1,21 @@
 import Operator from '../Operator';
 import Subscriber from '../Subscriber';
+import ArgumentOutOfRangeError from '../util/ArgumentOutOfRangeError';
+import EmptyObservable from '../observables/EmptyObservable';
 
 export default function take(total) {
-  return this.lift(new TakeOperator(total));
+  if (total === 0) {
+    return new EmptyObservable();
+  } else {
+    return this.lift(new TakeOperator(total));
+  }
 }
 
 class TakeOperator<T, R> implements Operator<T, R> {
   constructor(private total: number) {
+    if (this.total < 0) {
+      throw new ArgumentOutOfRangeError;
+    }
   }
 
   call(subscriber: Subscriber<T>): Subscriber<T> {