fix: predicates that return any will now behave property with findI…

…ndex (#6097) * test: add failing test for findIndex * fix: remove incompatible-with-any findIndex sig * chore: update api_guardian * test: remove now-irrelevant test
ReactiveX · Mar 8, 2021 · c6f73d6 · c6f73d6
1 parent 868e409
commit c6f73d6
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Showing 3 changed files with 6 additions and 5 deletions.
diff --git a/api_guard/dist/types/operators/index.d.ts b/api_guard/dist/types/operators/index.d.ts
@@ -124,7 +124,6 @@ export declare function find<T>(predicate: BooleanConstructor): OperatorFunction
 export declare function find<T, S extends T>(predicate: (value: T, index: number, source: Observable<T>) => value is S, thisArg?: any): OperatorFunction<T, S | undefined>;
 export declare function find<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): OperatorFunction<T, T | undefined>;
 
-export declare function findIndex<T>(predicate: (value: T, index: number, source: Observable<T>) => false, thisArg?: any): OperatorFunction<T, -1>;
 export declare function findIndex<T>(predicate: BooleanConstructor, thisArg?: any): OperatorFunction<T, T extends Falsy ? -1 : number>;
 export declare function findIndex<T>(predicate: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): OperatorFunction<T, number>;
 

diff --git a/spec-dtslint/operators/findIndex-spec.ts b/spec-dtslint/operators/findIndex-spec.ts
@@ -36,6 +36,9 @@ it('should support Boolean constructor', () => {
   const b = of(0 as const, -0 as const, null, 'hi there' as const, undefined, false as const, '' as const).pipe(findIndex(Boolean)); // $ExpectType Observable<number>
 });
 
-it('should properly narrow an always false predicate', () => {
-  const a = of('foo', 'bar', 'baz').pipe(findIndex(() => false)); // $ExpectType Observable<-1>
-})
+it('should support inference from a predicate that returns any', () => {
+  function isTruthy(value: number): any {
+    return !!value;
+  }
+  const a = of(1).pipe(findIndex(isTruthy)); // $ExpectType Observable<number>
+});
diff --git a/src/internal/operators/findIndex.ts b/src/internal/operators/findIndex.ts
@@ -3,7 +3,6 @@ import { Falsy, OperatorFunction } from '../types';
 import { operate } from '../util/lift';
 import { createFind } from './find';
 
-export function findIndex<T>(predicate: (value: T, index: number, source: Observable<T>) => false, thisArg?: any): OperatorFunction<T, -1>;
 export function findIndex<T>(predicate: BooleanConstructor, thisArg?: any): OperatorFunction<T, T extends Falsy ? -1 : number>;
 export function findIndex<T>(
   predicate: (value: T, index: number, source: Observable<T>) => boolean,