fix(transducers): fix #310, update flatten/flattenWith

- fix `flatten()`/`flattenWith()` return types - update generics to allow specifying explicit result type, but use new `DeepArrayValue<A>` mapped type as default - update `flattenWith()` predicate arg type to `any` since current restriction on top-level input type was (potentially) wrong for deeper levels. Also lift restriction and update pred's return type to `MaybeIterable<any>` (for same reason).
thi-ng · Aug 27, 2021 · bfbd726 · bfbd726
1 parent a309fac
commit bfbd726
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Showing 2 changed files with 19 additions and 16 deletions.
diff --git a/packages/transducers/src/xform/flatten-with.ts b/packages/transducers/src/xform/flatten-with.ts
@@ -1,4 +1,4 @@
-import type { Fn, Nullable } from "@thi.ng/api";
+import type { DeepArrayValue, Fn, Nullable } from "@thi.ng/api";
 import { isIterable, isString } from "@thi.ng/checks";
 import type { Reducer, Transducer } from "../api";
 import { compR } from "../func/compr";
@@ -36,20 +36,20 @@ type MaybeIterable<T> = Nullable<Iterable<T>>;
  * @param fn -
  * @param src -
  */
-export function flattenWith<T>(
-    fn: Fn<T, MaybeIterable<T>>
-): Transducer<T | Iterable<T>, T>;
-export function flattenWith<T>(
-    fn: Fn<T, MaybeIterable<T>>,
-    src: Iterable<T | Iterable<T>>
-): IterableIterator<T>;
-export function flattenWith<T>(
-    fn: Fn<T, MaybeIterable<T>>,
-    src?: Iterable<T | Iterable<T>>
+export function flattenWith<A, B = DeepArrayValue<A>>(
+    fn: Fn<any, MaybeIterable<any>>
+): Transducer<A, B>;
+export function flattenWith<A, B = DeepArrayValue<A>>(
+    fn: Fn<any, MaybeIterable<any>>,
+    src: Iterable<A>
+): IterableIterator<B>;
+export function flattenWith<A>(
+    fn: Fn<any, MaybeIterable<any>>,
+    src?: Iterable<A>
 ): any {
     return isIterable(src)
         ? iterator(flattenWith(fn), isString(src) ? <any>[src] : src)
-        : (rfn: Reducer<any, T>) => {
+        : (rfn: Reducer<any, A>) => {
               const reduce = rfn[2];
               const flatten = (acc: any, x: any) => {
                   const xx = fn(x);

diff --git a/packages/transducers/src/xform/flatten.ts b/packages/transducers/src/xform/flatten.ts
@@ -1,3 +1,4 @@
+import type { DeepArrayValue } from "@thi.ng/api";
 import { isNotStringAndIterable } from "@thi.ng/checks";
 import type { Transducer } from "../api";
 import { flattenWith } from "./flatten-with";
@@ -21,10 +22,12 @@ import { flattenWith } from "./flatten-with";
  *
  * @param src -
  */
-export function flatten<T>(): Transducer<T | Iterable<T>, T>;
-export function flatten<T>(src: Iterable<T | Iterable<T>>): IterableIterator<T>;
-export function flatten<T>(src?: Iterable<T | Iterable<T>>): any {
-    return flattenWith(
+export function flatten<A, B = DeepArrayValue<A>>(): Transducer<A, B>;
+export function flatten<A, B = DeepArrayValue<A>>(
+    src: Iterable<A>
+): IterableIterator<B>;
+export function flatten(src?: Iterable<any>): any {
+    return flattenWith<any, any>(
         (x) => (isNotStringAndIterable(x) ? x : undefined),
         src!
     );