From 761585957f887cc0fc3a9f8984e791fbc053e654 Mon Sep 17 00:00:00 2001
From: vmladenov <v.mladenov@hotmail.com>
Date: Sun, 2 Nov 2025 18:38:19 +0100
Subject: [PATCH] feat: enhance flat to support recursive flattening with depth
 -1

---
 src/iterables/select-many.ts  | 2 +-
 test/unit/select-many.spec.ts | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/iterables/select-many.ts b/src/iterables/select-many.ts
index d58dd2d..896adb6 100644
--- a/src/iterables/select-many.ts
+++ b/src/iterables/select-many.ts
@@ -29,7 +29,7 @@ export function flatMapIterator<TValue, TResult>(input: Iterable<TValue>, mapper
 export function* flatGenerator<TValue>(input: Iterable<TValue>, depth: number, level: number): Generator<TValue> {
     for (const item of input) {
         if (Array.isArray(item)) {
-            if (level >= depth) {
+            if (depth > 0 && level >= depth) {
                 yield item;
             } else {
                 level++;
diff --git a/test/unit/select-many.spec.ts b/test/unit/select-many.spec.ts
index 243881f..7407e4e 100644
--- a/test/unit/select-many.spec.ts
+++ b/test/unit/select-many.spec.ts
@@ -110,6 +110,15 @@ describe('select many tests', () => {
         expect(output).toStrictEqual([1, 2, 3, 4, 5, 6, 'a', 'b', 'c', 'd', 'e']);
     });
 
+    it('should flat sequence recursive: depth -1', () => {
+        const input = [
+            [1, 2, 3, 4, [5, 6, [7, [8, [9, [10, 11, [12]]]]]]],
+            'e'
+        ];
+        const output = from(input).flat(-1).toArray();
+        expect(output).toStrictEqual([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 'e']);
+    });
+
     it('should flatMap sequence', () => {
         const input = [
             [1, 2, 3, 4, [5, 6]],