v2: perf(request): optimize newHeadersFromIncoming and signal fast-path

[GavinMeierSonos]

Summary

• newHeadersFromIncoming: use direct array indexing with cached length instead of computed-property destructuring, avoiding intermediate object allocation on every header pair
• signal property: bypass getRequestCache() (full Request construction) for known HTTP methods, calling getAbortController().signal directly. Unknown/forbidden methods still fall through to getRequestCache() which preserves the throwing behaviour for invalid method names

Changes

• src/request.ts

[usualoma]

Hi @GavinMeierSonos,
Thank you creating pull request

newHeadersFromIncoming

This will certainly result in a slight but definite improvement.

signal

Since signal is almost always used for long-running requests, it may seem unnecessary for performance improvements; however, semantically, this[getAbortController]().signal is the correct approach.

Also, since there is no need to verify that it is a known method, would it be okay to implement it as follows, including changes to the test expectations?

diff --git i/src/request.ts w/src/request.ts
index ddac6c8..dbc4113 100644
--- i/src/request.ts
+++ w/src/request.ts
@@ -465,27 +465,11 @@ const requestPrototype: Record<string | symbol, any> = {
     }
     return false
   },
-}
-Object.defineProperty(requestPrototype, 'signal', {
-  get() {
-    // Fast path: known-valid methods don't need full Request construction.
-    switch (this[methodKey] as string) {
-      case 'GET':
-      case 'HEAD':
-      case 'POST':
-      case 'PUT':
-      case 'DELETE':
-      case 'OPTIONS':
-      case 'PATCH':
-      case 'TRACE':
-        return this[getAbortController]().signal
-      default:
-        // Unknown/forbidden methods fall through to getRequestCache() which throws
-        // for methods like 'connect', 'track', non-uppercase 'trace', etc.
-        return this[getRequestCache]().signal
-    }
+
+  get signal() {
+    return this[getAbortController]().signal
   },
-})
+}
 ;[
   'cache',
   'credentials',
diff --git i/test/request.test.ts w/test/request.test.ts
index 03f3c56..bc3e18d 100644
--- i/test/request.test.ts
+++ w/test/request.test.ts
@@ -617,11 +617,12 @@ describe('Request', () => {
       }
 
       for (const method of ['trace', 'TrAcE']) {
-        const reqBeforeSignal = createTraceLikeRequest(method)
-        await expect(reqBeforeSignal.text()).rejects.toBeInstanceOf(TypeError)
+        const req = createTraceLikeRequest(method)
+        await expect(req.text()).rejects.toBeInstanceOf(TypeError)
 
         const reqAfterSignal = createTraceLikeRequest(method)
-        expect(() => reqAfterSignal.signal).toThrow(/HTTP method is unsupported/)
+        expect(() => reqAfterSignal.signal).not.toThrow()
+        await expect(reqAfterSignal.text()).rejects.toBeInstanceOf(TypeError)
       }
     })

[usualoma]

As a reviewer, I’d also like you to understand that, aside from splitting pull requests, having commits split appropriately makes the review process much less burdensome.

[GavinMeierSonos]

@usualoma yeah I can make that happen. Thank you for the review.

[yusukebe]

LGTM!

[yusukebe]

@usualoma I fixed the format error. Can you review this again?

[usualoma]

I think we can merge it!

[GavinMeierSonos]

@usualoma @yusukebe Awesome 🚀

Thank you! I will take a look at the comments on the other PR as well and address those!