fix(partition): deprecate partition operator and create partition sta…

…tic function (ReactiveX#4419)

spec-dtslint/observables/partition-spec.ts

@@ -0,0 +1,20 @@
+import { of, partition } from 'rxjs';
+
+it('should infer correctly', () => {
+  const o = partition(of('a', 'b', 'c'), (value, index) => true); // $ExpectType [Observable<string>, Observable<string>]
+  const p = partition(of('a', 'b', 'c'), () => true); // $ExpectType [Observable<string>, Observable<string>]
+});
+
+it('should accept a thisArg parameter', () => {
+  const o = partition(of('a', 'b', 'c'), () => true, 5); // $ExpectType [Observable<string>, Observable<string>]
+});
+
+it('should enforce predicate', () => {
+  const o = partition(of('a', 'b', 'c')); // $ExpectError
+});
+
+it('should enforce predicate types', () => {
+  const o = partition(of('a', 'b', 'c'), 'nope'); // $ExpectError
+  const p = partition(of('a', 'b', 'c'), (value: number) => true); // $ExpectError
+  const q = partition(of('a', 'b', 'c'), (value, index: string) => true); // $ExpectError
+});

spec/operators/partition-spec.ts.disabled → spec/observables/partition-spec.ts

@@ -1,16 +1,13 @@
 import { expect } from 'chai';
-import * as Rx from 'rxjs/Rx';
+import { Observable, partition, of } from 'rxjs';
+import { map, mergeMap } from 'rxjs/operators';
 import { hot, cold, expectObservable, expectSubscriptions } from '../helpers/marble-testing';
 
-// TODO: The imports on these tests can't be modernized until we do away with
-// the partition "operator" and make it a creation method.
 declare function asDiagram(arg: string): Function;
 
-const Observable = Rx.Observable;
-
 /** @test {partition} */
 describe('Observable.prototype.partition', () => {
-  function expectObservableArray(result: Rx.Observable<string>[], expected: string[]) {
+  function expectObservableArray(result: Observable<string>[], expected: string[]) {
     for (let idx = 0; idx < result.length; idx++ ) {
       expectObservable(result[idx]).toBe(expected[idx]);
     }
@@ -23,7 +20,7 @@ describe('Observable.prototype.partition', () => {
     const expected = ['--1-----3---------5------|',
                     '----2----------4------6--|'];
 
-    const result = e1.partition((x: any) => x % 2 === 1);
+    const result = partition(e1, (x: any) => x % 2 === 1);
 
     expectObservableArray(result, expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
@@ -39,7 +36,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -53,7 +50,7 @@ describe('Observable.prototype.partition', () => {
       return index % 2 === 0;
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -67,7 +64,7 @@ describe('Observable.prototype.partition', () => {
       return x === this.value;
     }
 
-    expectObservableArray(e1.partition(predicate, {value: 'a'}), expected);
+    expectObservableArray(partition(e1, predicate, {value: 'a'}), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -81,7 +78,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -95,7 +92,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -115,7 +112,7 @@ describe('Observable.prototype.partition', () => {
       return match;
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -129,7 +126,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'x';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -143,7 +140,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'x';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -157,7 +154,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -171,7 +168,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -185,7 +182,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -199,7 +196,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -213,7 +210,7 @@ describe('Observable.prototype.partition', () => {
       return x === 'a';
     }
 
-    expectObservableArray(e1.partition(predicate), expected);
+    expectObservableArray(partition(e1, predicate), expected);
     expectSubscriptions(e1.subscriptions).toBe([e1subs, e1subs]);
   });
 
@@ -227,7 +224,7 @@ describe('Observable.prototype.partition', () => {
     function predicate(x: string) {
       return x === 'a';
     }
-    const result = e1.partition(predicate);
+    const result = partition(e1, predicate);
 
     for (let idx = 0; idx < result.length; idx++ ) {
       expectObservable(result[idx], unsub).toBe(expected[idx]);
@@ -242,11 +239,10 @@ describe('Observable.prototype.partition', () => {
                     '----b---          '];
     const unsub =     '       !          ';
 
-    const result = e1
-      .mergeMap((x: string) => Observable.of(x))
-      .partition((x: string) => x === 'a')
-      .map((observable: Rx.Observable<string>) =>
-        observable.mergeMap((x: string) => Observable.of(x)));
+    const e1Pipe = e1.pipe(
+      mergeMap((x: string) => of(x))
+    );
+    const result = partition(e1Pipe, (x: string) => x === 'a');
 
     expectObservable(result[0], unsub).toBe(expected[0]);
     expectObservable(result[1], unsub).toBe(expected[1]);
@@ -256,10 +252,10 @@ describe('Observable.prototype.partition', () => {
   it('should accept thisArg', () => {
     const thisArg = {};
 
-    Observable.of(1).partition(function (this: any, value: number) {
+    partition(of(1), function (this: any, value: number) {
       expect(this).to.deep.equal(thisArg);
       return true;
     }, thisArg)
-      .forEach((observable: Rx.Observable<number>) => observable.subscribe());
+      .forEach((observable: Observable<number>) => observable.subscribe());
   });
 });

src/index.ts

@@ -58,6 +58,7 @@ export { never } from './internal/observable/never';
 export { of } from './internal/observable/of';
 export { onErrorResumeNext } from './internal/observable/onErrorResumeNext';
 export { pairs } from './internal/observable/pairs';
+export { partition } from './internal/observable/partition';
 export { race } from './internal/observable/race';
 export { range } from './internal/observable/range';
 export { throwError } from './internal/observable/throwError';

src/internal/observable/partition.ts

@@ -0,0 +1,67 @@
+import { not } from '../util/not';
+import { subscribeTo } from '../util/subscribeTo';
+import { filter } from '../operators/filter';
+import { ObservableInput } from '../types';
+import { Observable } from '../Observable';
+
+/**
+ * Splits the source Observable into two, one with values that satisfy a
+ * predicate, and another with values that don't satisfy the predicate.
+ *
+ * <span class="informal">It's like {@link filter}, but returns two Observables:
+ * one like the output of {@link filter}, and the other with values that did not
+ * pass the condition.</span>
+ *
+ * ![](partition.png)
+ *
+ * `partition` outputs an array with two Observables that partition the values
+ * from the source Observable through the given `predicate` function. The first
+ * Observable in that array emits source values for which the predicate argument
+ * returns true. The second Observable emits source values for which the
+ * predicate returns false. The first behaves like {@link filter} and the second
+ * behaves like {@link filter} with the predicate negated.
+ *
+ * ## Example
+ * Partition a set of numbers into odds and evens observables
+ * ```ts
+ * import { of, partition } from 'rxjs';
+ *
+ * const observableValues = of(1, 2, 3, 4, 5, 6);
+ * const [evens$, odds$] = partition(observableValues, (value, index) => value % 2 === 0);
+ *
+ * odds$.subscribe(x => console.log('odds', x));
+ * evens$.subscribe(x => console.log('evens', x));
+ *
+ * // Logs:
+ * // odds 1
+ * // odds 3
+ * // odds 5
+ * // evens 2
+ * // evens 4
+ * // evens 6
+ * ```
+ *
+ * @see {@link filter}
+ *
+ * @param {function(value: T, index: number): boolean} predicate A function that
+ * evaluates each value emitted by the source Observable. If it returns `true`,
+ * the value is emitted on the first Observable in the returned array, if
+ * `false` the value is emitted on the second Observable in the array. The
+ * `index` parameter is the number `i` for the i-th source emission that has
+ * happened since the subscription, starting from the number `0`.
+ * @param {any} [thisArg] An optional argument to determine the value of `this`
+ * in the `predicate` function.
+ * @return {[Observable<T>, Observable<T>]} An array with two Observables: one
+ * with values that passed the predicate, and another with values that did not
+ * pass the predicate.
+ */
+export function partition<T>(
+  source: ObservableInput<T>,
+  predicate: (value: T, index: number) => boolean,
+  thisArg?: any
+): [Observable<T>, Observable<T>] {
+  return [
+    filter(predicate, thisArg)(new Observable<T>(subscribeTo(source))),
+    filter(not(predicate, thisArg) as any)(new Observable<T>(subscribeTo(source)))
+  ] as [Observable<T>, Observable<T>];
+}

src/internal/operators/partition.ts

@@ -50,6 +50,9 @@ import { UnaryFunction } from '../types';
  * @method partition
  * @owner Observable
  */
+/**
+ * @deprecated use `partition` static creation function instead
+ */
 export function partition<T>(predicate: (value: T, index: number) => boolean,
                              thisArg?: any): UnaryFunction<Observable<T>, [Observable<T>, Observable<T>]> {
   return (source: Observable<T>) => [