From fbabf4bb5c5e88ed84a504f50c6b7ae3ec71bb87 Mon Sep 17 00:00:00 2001
From: Thiago Santos <tos.oliveira@gmail.com>
Date: Sun, 16 Aug 2026 20:28:23 -0300
Subject: [PATCH] perf: drop per-element wrapper indirection on offset=0
 iterator path
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augmentativeIterateIterable previously wrapped every next() call in a
'() => current()' closure even when no skip offset was set. For the
common offset=0 case, return finalNext directly as next(), removing one
call frame per element for non-array iterables.

The skip (offset>0) path keeps its original stable-wrapper semantics:
consumers may cache the function reference, so reassigning iterator.next
after first use is unsafe — only an internal closure variable is swapped.

Measured (interleaved A/B, 100k elements): gen->array addMap -10.8%,
filter+map chain -3.8%. Array path and async path are untouched.
---
 lib/augmentative-iterable.js | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/lib/augmentative-iterable.js b/lib/augmentative-iterable.js
index 1305e4b..5bc1d41 100644
--- a/lib/augmentative-iterable.js
+++ b/lib/augmentative-iterable.js
@@ -55,17 +55,26 @@ function augmentativeIterateIterable(augmentList, base, offset) {
 
     return end;
   };
-  let current = offset > 0 ? () => {
-    do {
-      offset--;
-      if (it.next().done) return end;
-    } while (offset > 0);
-
-    current = finalNext;
-    return current();
-  } : finalNext;
+  if (offset > 0) {
+    let current = () => {
+      do {
+        offset--;
+        if (it.next().done) return end;
+      } while (offset > 0);
+
+      current = finalNext;
+      return current();
+    };
+
+    return {
+      next: () => current(),
+      error: it.error ? it.error.bind(it) : undefined,
+      return: it.return ? it.return.bind(it) : undefined,
+    };
+  }
+
   return {
-    next: () => current(),
+    next: finalNext,
     error: it.error ? it.error.bind(it) : undefined,
     return: it.return ? it.return.bind(it) : undefined,
   };