fix: do not overwrite Content-Length in the fast path pattern if Content-Length already exists. (#309)

usualoma · web-flow · commit c94489955ebd · 2026-03-05T11:13:02.000+09:00
* fix: do not overwrite Content-Length in the fast path pattern if Content-Length already exists.

* fix: support tuple headers in responseViaCache
diff --git a/src/listener.ts b/src/listener.ts
@@ -70,17 +70,35 @@ const responseViaCache = async (
 ): Promise<undefined | void> => {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   let [status, body, header] = (res as any)[cacheKey] as InternalCache
-  if (header instanceof Headers) {
+
+  let hasContentLength = false
+  if (!header) {
+    header = { 'content-type': 'text/plain; charset=UTF-8' }
+  } else if (header instanceof Headers) {
+    hasContentLength = header.has('content-length')
     header = buildOutgoingHttpHeaders(header)
+  } else if (Array.isArray(header)) {
+    const headerObj = new Headers(header)
+    hasContentLength = headerObj.has('content-length')
+    header = buildOutgoingHttpHeaders(headerObj)
+  } else {
+    for (const key in header) {
+      if (key.length === 14 && key.toLowerCase() === 'content-length') {
+        hasContentLength = true
+        break
+      }
+    }
   }
 
   // in `responseViaCache`, if body is not stream, Transfer-Encoding is considered not chunked
-  if (typeof body === 'string') {
-    header['Content-Length'] = Buffer.byteLength(body)
-  } else if (body instanceof Uint8Array) {
-    header['Content-Length'] = body.byteLength
-  } else if (body instanceof Blob) {
-    header['Content-Length'] = body.size
+  if (!hasContentLength) {
+    if (typeof body === 'string') {
+      header['Content-Length'] = Buffer.byteLength(body)
+    } else if (body instanceof Uint8Array) {
+      header['Content-Length'] = body.byteLength
+    } else if (body instanceof Blob) {
+      header['Content-Length'] = body.size
+    }
   }
 
   outgoing.writeHead(status, header)
diff --git a/src/response.ts b/src/response.ts
@@ -10,7 +10,7 @@ export const cacheKey = Symbol('cache')
 export type InternalCache = [
   number,
   string | ReadableStream,
-  Record<string, string> | Headers | OutgoingHttpHeaders,
+  Record<string, string> | [string, string][] | Headers | OutgoingHttpHeaders | undefined,
 ]
 interface LightResponse {
   [responseCache]?: globalThis.Response
@@ -28,7 +28,7 @@ export class Response {
   }
 
   constructor(body?: BodyInit | null, init?: ResponseInit) {
-    let headers: HeadersInit
+    let headers: HeadersInit | undefined
     this.#body = body
     if (init instanceof Response) {
       const cachedGlobalResponse = (init as any)[responseCache]
@@ -52,16 +52,17 @@ export class Response {
       body instanceof Blob ||
       body instanceof Uint8Array
     ) {
-      headers ||= init?.headers || { 'content-type': 'text/plain; charset=UTF-8' }
-      ;(this as any)[cacheKey] = [init?.status || 200, body, headers]
+      ;(this as any)[cacheKey] = [init?.status || 200, body, headers || init?.headers]
     }
   }
 
   get headers(): Headers {
     const cache = (this as LightResponse)[cacheKey] as InternalCache
     if (cache) {
       if (!(cache[2] instanceof Headers)) {
-        cache[2] = new Headers(cache[2] as HeadersInit)
+        cache[2] = new Headers(
+          (cache[2] || { 'content-type': 'text/plain; charset=UTF-8' }) as HeadersInit
+        )
       }
       return cache[2]
     }
diff --git a/test/server.test.ts b/test/server.test.ts
@@ -242,6 +242,37 @@ describe('various response body types', () => {
         })
         return response
       })
+      app.get('/text-with-content-length-object', () => {
+        const response = new Response('Hello Hono!', {
+          headers: { 'content-type': 'text/plain', 'content-length': '00011' },
+        })
+        return response
+      })
+      app.get('/text-with-content-length-headers', () => {
+        const response = new Response('Hello Hono!', {
+          headers: new Headers({ 'content-type': 'text/plain', 'content-length': '00011' }),
+        })
+        return response
+      })
+      app.get('/text-with-content-length-array', () => {
+        const response = new Response('Hello Hono!', {
+          headers: [
+            ['content-type', 'text/plain'],
+            ['content-length', '00011'],
+          ],
+        })
+        return response
+      })
+      app.get('/text-with-set-cookie-array', () => {
+        const response = new Response('Hello Hono!', {
+          headers: [
+            ['content-type', 'text/plain'],
+            ['set-cookie', 'a=1'],
+            ['set-cookie', 'b=2'],
+          ],
+        })
+        return response
+      })
 
       app.use('/etag/*', etag())
       app.get('/etag/buffer', () => {
@@ -372,6 +403,38 @@ describe('various response body types', () => {
       expect(res.text).toBe('Hello Hono!')
     })
 
+    it('Should return 200 response - GET /text-with-content-length-object', async () => {
+      const res = await request(server).get('/text-with-content-length-object')
+      expect(res.status).toBe(200)
+      expect(res.headers['content-type']).toMatch('text/plain')
+      expect(res.headers['content-length']).toBe('00011')
+      expect(res.text).toBe('Hello Hono!')
+    })
+
+    it('Should return 200 response - GET /text-with-content-length-headers', async () => {
+      const res = await request(server).get('/text-with-content-length-headers')
+      expect(res.status).toBe(200)
+      expect(res.headers['content-type']).toMatch('text/plain')
+      expect(res.headers['content-length']).toBe('00011')
+      expect(res.text).toBe('Hello Hono!')
+    })
+
+    it('Should return 200 response - GET /text-with-content-length-array', async () => {
+      const res = await request(server).get('/text-with-content-length-array')
+      expect(res.status).toBe(200)
+      expect(res.headers['content-type']).toMatch('text/plain')
+      expect(res.headers['content-length']).toBe('00011')
+      expect(res.text).toBe('Hello Hono!')
+    })
+
+    it('Should return 200 response - GET /text-with-set-cookie-array', async () => {
+      const res = await request(server).get('/text-with-set-cookie-array')
+      expect(res.status).toBe(200)
+      expect(res.headers['content-type']).toMatch('text/plain')
+      expect(res.headers['set-cookie']).toEqual(['a=1', 'b=2'])
+      expect(res.text).toBe('Hello Hono!')
+    })
+
     it('Should return 200 response - GET /etag/buffer', async () => {
       const res = await request(server).get('/etag/buffer')
       expect(res.status).toBe(200)
