Synchronize response metadata when replacing bodies

.changeset/fix-http-server-response-body-headers.md

@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Synchronize HTTP server response content headers when replacing the body.

packages/effect/src/unstable/http/HttpClientRequest.ts

@@ -28,6 +28,7 @@ import * as Stream from "../../Stream.ts"
 import * as Headers from "./Headers.ts"
 import * as HttpBody from "./HttpBody.ts"
 import { hasBody, type HttpMethod } from "./HttpMethod.ts"
+import * as bodyInternal from "./internal/httpBody.ts"
 import * as Url from "./Url.ts"
 import * as UrlParams from "./UrlParams.ts"
 
@@ -649,25 +650,12 @@ export const setBody: {
   (body: HttpBody.HttpBody): (self: HttpClientRequest) => HttpClientRequest
   (self: HttpClientRequest, body: HttpBody.HttpBody): HttpClientRequest
 } = dual(2, (self: HttpClientRequest, body: HttpBody.HttpBody): HttpClientRequest => {
-  let headers = self.headers
-  if (body._tag === "Empty" || body._tag === "FormData") {
-    headers = Headers.remove(Headers.remove(headers, "Content-Type"), "Content-length")
-  } else {
-    if (body.contentType) {
-      headers = Headers.set(headers, "content-type", body.contentType)
-    }
-    if (body.contentLength !== undefined) {
-      headers = Headers.set(headers, "content-length", body.contentLength.toString())
-    } else {
-      headers = Headers.remove(headers, "content-length")
-    }
-  }
   return makeWith(
     self.method,
     self.url,
     self.urlParams,
     self.hash,
-    headers,
+    bodyInternal.updateHeaders(self.headers, body),
     body
   )
 })

packages/effect/src/unstable/http/HttpServerResponse.ts

@@ -34,6 +34,7 @@ import * as HttpClientRequest from "./HttpClientRequest.ts"
 import * as HttpClientResponse from "./HttpClientResponse.ts"
 import * as HttpIncomingMessage from "./HttpIncomingMessage.ts"
 import type { HttpPlatform } from "./HttpPlatform.ts"
+import * as bodyInternal from "./internal/httpBody.ts"
 import * as Template from "./Template.ts"
 import * as UrlParams from "./UrlParams.ts"
 
@@ -931,7 +932,8 @@ export const setBody: {
   (self: HttpServerResponse, body: Body.HttpBody): HttpServerResponse
 } = dual(
   2,
-  (self: HttpServerResponse, body: Body.HttpBody): HttpServerResponse => makeResponse({ ...self, body })
+  (self: HttpServerResponse, body: Body.HttpBody): HttpServerResponse =>
+    makeResponse({ ...self, headers: bodyInternal.updateHeaders(self.headers, body), body })
 )
 
 /**
@@ -1345,13 +1347,13 @@ const makeResponse = (options: {
   self.body = options.body ?? Body.empty
   if (
     self.body._tag !== "Empty" &&
-    (self.body.contentType || self.body.contentLength)
+    (self.body.contentType || self.body.contentLength !== undefined)
   ) {
     const newHeaders = Headers.fromRecordUnsafe({ ...options.headers }) as any
     if (self.body.contentType) {
       newHeaders["content-type"] = self.body.contentType
     }
-    if (self.body.contentLength) {
+    if (self.body.contentLength !== undefined) {
       newHeaders["content-length"] = self.body.contentLength.toString()
     }
     self.headers = newHeaders

packages/effect/src/unstable/http/internal/httpBody.ts

@@ -0,0 +1,15 @@
+import * as Headers from "../Headers.ts"
+import type * as HttpBody from "../HttpBody.ts"
+
+/** @internal */
+export const updateHeaders = (headers: Headers.Headers, body: HttpBody.HttpBody): Headers.Headers => {
+  if (body._tag === "Empty" || body._tag === "FormData") {
+    return Headers.remove(Headers.remove(headers, "content-type"), "content-length")
+  }
+  headers = body.contentType === undefined
+    ? Headers.remove(headers, "content-type")
+    : Headers.set(headers, "content-type", body.contentType)
+  return body.contentLength === undefined
+    ? Headers.remove(headers, "content-length")
+    : Headers.set(headers, "content-length", body.contentLength.toString())
+}

packages/effect/test/unstable/http/HttpServerResponse.test.ts

@@ -1,6 +1,6 @@
 import { assert, describe, it } from "@effect/vitest"
 import { Context, Effect, Stream } from "effect"
-import { HttpClientRequest, HttpClientResponse, HttpServerResponse } from "effect/unstable/http"
+import { HttpBody, HttpClientRequest, HttpClientResponse, HttpServerResponse } from "effect/unstable/http"
 
 const TestValue = Context.Reference<number>("test/TestValue", { defaultValue: () => 0 })
 
@@ -75,4 +75,20 @@ describe("HttpServerResponse", () => {
       assert.strictEqual(response.status, 200)
       assert.strictEqual(yield* roundTrip.text, "")
     }))
+
+  it("synchronizes body metadata headers for empty and replaced bodies", () => {
+    const emptyBytes = HttpServerResponse.uint8Array(new Uint8Array())
+    assert.strictEqual(emptyBytes.headers["content-length"], "0")
+
+    const replaced = HttpServerResponse.setBody(HttpServerResponse.text("abc"), HttpBody.empty)
+    assert.notProperty(replaced.headers, "content-type")
+    assert.notProperty(replaced.headers, "content-length")
+
+    const streamed = HttpServerResponse.setBody(
+      HttpServerResponse.text("abc"),
+      HttpBody.stream(Stream.empty, "application/octet-stream")
+    )
+    assert.strictEqual(streamed.headers["content-type"], "application/octet-stream")
+    assert.notProperty(streamed.headers, "content-length")
+  })
 })