Split: Add support for longer strings (#1042)

sindresorhus · Jan 16, 2025 · 49605b9 · 49605b9
1 parent bf5ce3c
commit 49605b9
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Showing 2 changed files with 19 additions and 4 deletions.
diff --git a/source/split.d.ts b/source/split.d.ts
@@ -22,8 +22,14 @@ array = split(items, ',');
 export type Split<
 	S extends string,
 	Delimiter extends string,
+> = SplitHelper<S, Delimiter>;
+
+type SplitHelper<
+	S extends string,
+	Delimiter extends string,
+	Accumulator extends string[] = [],
 > = S extends `${infer Head}${Delimiter}${infer Tail}`
-	? [Head, ...Split<Tail, Delimiter>]
-	: S extends Delimiter
-		? []
-		: [S];
+	? SplitHelper<Tail, Delimiter, [...Accumulator, Head]>
+	: Delimiter extends ''
+		? Accumulator
+		: [...Accumulator, S];
diff --git a/test-d/split.ts b/test-d/split.ts
@@ -1,5 +1,6 @@
 import {expectType} from 'tsd';
 import type {Split} from '../index';
+import type {BuildTuple} from '../source/internal';
 
 declare function split<
 	S extends string,
@@ -28,3 +29,11 @@ expectType<[]>(split('', ''));
 
 // Split empty string by any string.
 expectType<['']>(split('', ' '));
+
+// Recursion depth at which a non-tail recursive implementation starts to fail.
+const fiftyZeroes = '00000000000000000000000000000000000000000000000000';
+expectType<BuildTuple<50, '0'>>(split(fiftyZeroes, ''));
+
+// Maximum allowed recursion depth for a tail recursive implementation.
+const nineHundredNinetyNineZeroes = '000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000';
+expectType<BuildTuple<999, '0'>>(split(nineHundredNinetyNineZeroes, ''));