From 6d901cbb0c0f2aa3fc5a02ef895cc9e9a7a09243 Mon Sep 17 00:00:00 2001
From: Nicholas Jamieson <nicholas@cartant.com>
Date: Fri, 7 Feb 2020 12:07:21 +1000
Subject: [PATCH] fix: support N args in static race and ensure observable
 returned (#5286)

* test: add failing test for race

* fix: use from on ObservableInput

* fix: support N args for static race

* chore: use dtslint helpers
---
 spec-dtslint/observables/race-spec.ts | 122 ++++----------------------
 spec/observables/race-spec.ts         |   8 ++
 src/internal/observable/race.ts       |  31 ++-----
 3 files changed, 32 insertions(+), 129 deletions(-)

diff --git a/spec-dtslint/observables/race-spec.ts b/spec-dtslint/observables/race-spec.ts
index ff7e83aae0..540a153df0 100644
--- a/spec-dtslint/observables/race-spec.ts
+++ b/spec-dtslint/observables/race-spec.ts
@@ -1,120 +1,32 @@
 import { race, of } from 'rxjs';
-
-it('should infer correctly with 1 parameter', () => {
-  const a = of(1);
-  const o = race(a); // $ExpectType Observable<number>
-});
+import { a$, b, b$, c, c$, d$, e$, f$ } from '../helpers';
 
 describe('race(a, b, c)', () => {
-  it('should infer correctly with multiple parameters of the same type', () => {
-    const a = of(1);
-    const b = of(2);
-    const o = race(a, b); // $ExpectType Observable<number>
-  });
-
-  it('should support 2 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const o = race(a, b); // $ExpectType Observable<string | number>
-  });
-
-  it('should support 3 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const o = race(a, b, c); // $ExpectType Observable<string | number | boolean>
-  });
-
-  it('should support 4 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const o = race(a, b, c, d); // $ExpectType Observable<string | number | boolean | number[]>
-  });
-
-  it('should support 5 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const e = of(['blah']);
-    const o = race(a, b, c, d, e); // $ExpectType Observable<string | number | boolean | number[] | string[]>
-  });
-
-  it('should support 6 or more parameters of the same type', () => {
-    const a = of(1);
-    const o = race(a, a, a, a, a, a, a, a, a, a, a, a, a, a); // $ExpectType Observable<number>
-  });
-
-  it('should return unknown for 6 or more arguments of different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const e = of(['blah']);
-    const f = of({ foo: 'bar' });
-    const o = race(a, b, c, d, e, f); // $ExpectType Observable<unknown>
+  it('should support N arguments of different types', () => {
+    const o1 = race(a$); // $ExpectType Observable<A>
+    const o2 = race(a$, b$); // $ExpectType Observable<A | B>
+    const o3 = race(a$, b$, c$); // $ExpectType Observable<A | B | C>
+    const o4 = race(a$, b$, c$, d$); // $ExpectType Observable<A | B | C | D>
+    const o5 = race(a$, b$, c$, d$, e$); // $ExpectType Observable<A | B | C | D | E>
+    const o6 = race(a$, b$, c$, d$, e$, f$); // $ExpectType Observable<A | B | C | D | E | F>
   });
 });
 
 describe('race([a, b, c])', () => {
-  it('should infer correctly with multiple parameters of the same type', () => {
-    const a = of(1);
-    const b = of(2);
-    const o = race([a, b]); // $ExpectType Observable<number>
-  });
-
-  it('should support 2 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const o = race([a, b]); // $ExpectType Observable<string | number>
-  });
-
-  it('should support 3 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const o = race([a, b, c]); // $ExpectType Observable<string | number | boolean>
-  });
-
-  it('should support 4 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const o = race([a, b, c, d]); // $ExpectType Observable<string | number | boolean | number[]>
-  });
-
-  it('should support 5 parameters with different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const e = of(['blah']);
-    const o = race([a, b, c, d, e]); // $ExpectType Observable<string | number | boolean | number[] | string[]>
-  });
-
-  it('should support 6 or more parameters of the same type', () => {
-    const a = of(1);
-    const o = race([a, a, a, a, a, a, a, a, a, a, a, a, a, a]); // $ExpectType Observable<number>
-  });
-
-  it('should return {} for 6 or more arguments of different types', () => {
-    const a = of(1);
-    const b = of('a');
-    const c = of(true);
-    const d = of([1, 2, 3]);
-    const e = of(['blah']);
-    const f = of({ foo: 'bar' });
-    const o = race([a, b, c, d, e, f]); // $ExpectType Observable<unknown>
+  it('should support N arguments of different types', () => {
+    const o1 = race([a$]); // $ExpectType Observable<A>
+    const o2 = race([a$, b$]); // $ExpectType Observable<A | B>
+    const o3 = race([a$, b$, c$]); // $ExpectType Observable<A | B | C>
+    const o4 = race([a$, b$, c$, d$]); // $ExpectType Observable<A | B | C | D>
+    const o5 = race([a$, b$, c$, d$, e$]); // $ExpectType Observable<A | B | C | D | E>
+    const o6 = race([a$, b$, c$, d$, e$, f$]); // $ExpectType Observable<A | B | C | D | E | F>
   });
 });
 
 it('should race observable inputs', () => {
-  const o = race(of(1), Promise.resolve('foo'), [true, false]); // $ExpectType Observable<string | number | boolean>
+  const o = race(a$, Promise.resolve(b), [c]); // $ExpectType Observable<A | B | C>
 });
 
 it('should race an array observable inputs', () => {
-  const o = race([of(1), Promise.resolve('foo'), [true, false]]); // $ExpectType Observable<string | number | boolean>
+  const o = race([a$, Promise.resolve(b), [c]]); // $ExpectType Observable<A | B | C>
 });
diff --git a/spec/observables/race-spec.ts b/spec/observables/race-spec.ts
index 121fcd68cb..2dc3fa1d74 100644
--- a/spec/observables/race-spec.ts
+++ b/spec/observables/race-spec.ts
@@ -1,6 +1,7 @@
 import { hot, cold, expectObservable, expectSubscriptions } from '../helpers/marble-testing';
 import { race, of } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
+import { expect } from 'chai';
 
 /** @test {race} */
 describe('static race', () => {
@@ -204,4 +205,11 @@ describe('static race', () => {
     expectObservable(source).toBe(expected);
     expectSubscriptions(e1.subscriptions).toBe(e1subs);
   });
+
+  it('should support a single ObservableInput argument', (done: MochaDone) => {
+    const source = race(Promise.resolve(42));
+    source.subscribe(value => {
+      expect(value).to.equal(42);
+    }, done, done);
+  });
 });
diff --git a/src/internal/observable/race.ts b/src/internal/observable/race.ts
index 26b4db87e3..27929e52c7 100644
--- a/src/internal/observable/race.ts
+++ b/src/internal/observable/race.ts
@@ -1,34 +1,17 @@
 import { Observable } from '../Observable';
 import { isArray } from '../util/isArray';
+import { from } from './from';
 import { fromArray } from './fromArray';
 import { Operator } from '../Operator';
 import { Subscriber } from '../Subscriber';
 import { Subscription } from '../Subscription';
-import { TeardownLogic, ObservableInput } from '../types';
+import { TeardownLogic, ObservableInput, ObservedValueUnionFromArray } from '../types';
 import { OuterSubscriber } from '../OuterSubscriber';
 import { InnerSubscriber } from '../InnerSubscriber';
 import { subscribeToResult } from '../util/subscribeToResult';
 
-// tslint:disable:max-line-length
-export function race<A>(arg: [ObservableInput<A>]): Observable<A>;
-export function race<A, B>(arg: [ObservableInput<A>, ObservableInput<B>]): Observable<A | B>;
-export function race<A, B, C>(arg: [ObservableInput<A>, ObservableInput<B>, ObservableInput<C>]): Observable<A | B | C>;
-export function race<A, B, C, D>(arg: [ObservableInput<A>, ObservableInput<B>, ObservableInput<C>, ObservableInput<D>]): Observable<A | B | C | D>;
-export function race<A, B, C, D, E>(arg: [ObservableInput<A>, ObservableInput<B>, ObservableInput<C>, ObservableInput<D>, ObservableInput<E>]): Observable<A | B | C | D | E>;
-export function race<T>(arg: ObservableInput<T>[]): Observable<T>;
-export function race(arg: ObservableInput<any>[]): Observable<unknown>;
-
-export function race<A>(a: ObservableInput<A>): Observable<A>;
-export function race<A, B>(a: ObservableInput<A>, b: ObservableInput<B>): Observable<A | B>;
-export function race<A, B, C>(a: ObservableInput<A>, b: ObservableInput<B>, c: ObservableInput<C>): Observable<A | B | C>;
-export function race<A, B, C, D>(a: ObservableInput<A>, b: ObservableInput<B>, c: ObservableInput<C>, d: ObservableInput<D>): Observable<A | B | C | D>;
-export function race<A, B, C, D, E>(a: ObservableInput<A>, b: ObservableInput<B>, c: ObservableInput<C>, d: ObservableInput<D>, e: ObservableInput<E>): Observable<A | B | C | D | E>;
-// tslint:enable:max-line-length
-
-export function race<T>(observables: ObservableInput<T>[]): Observable<T>;
-export function race(observables: ObservableInput<any>[]): Observable<unknown>;
-export function race<T>(...observables: ObservableInput<T>[]): Observable<T>;
-export function race(...observables: ObservableInput<any>[]): Observable<unknown>;
+export function race<A extends ObservableInput<any>[]>(observables: A): Observable<ObservedValueUnionFromArray<A>>;
+export function race<A extends ObservableInput<any>[]>(...observables: A): Observable<ObservedValueUnionFromArray<A>>;
 
 /**
  * Returns an observable that mirrors the first source observable to emit an item.
@@ -71,14 +54,14 @@ export function race(...observables: ObservableInput<any>[]): Observable<unknown
  * @param {...Observables} ...observables sources used to race for which Observable emits first.
  * @return {Observable} an Observable that mirrors the output of the first Observable to emit an item.
  */
-export function race<T>(...observables: ObservableInput<any>[]): Observable<T> {
+export function race<T>(...observables: (ObservableInput<T> | ObservableInput<T>[])[]): Observable<any> {
   // if the only argument is an array, it was most likely called with
   // `race([obs1, obs2, ...])`
   if (observables.length === 1) {
     if (isArray(observables[0])) {
-      observables = observables[0] as Observable<any>[];
+      observables = observables[0] as ObservableInput<T>[];
     } else {
-      return observables[0] as Observable<T>;
+      return from(observables[0] as ObservableInput<T>);
     }
   }