From 590c1ccd0a21f7afe8c28fcc55ab1d0b5254fe72 Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@roe.dev>
Date: Tue, 28 Jul 2026 16:11:43 +0100
Subject: [PATCH] fix: invoke `end` callback when no chunk is passed

---
 src/stream/writable.ts |  5 ++++-
 test/index.test.ts     | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/src/stream/writable.ts b/src/stream/writable.ts
index adba5f1..ff1e704 100644
--- a/src/stream/writable.ts
+++ b/src/stream/writable.ts
@@ -96,12 +96,15 @@ export class Writable extends EventEmitter implements NodeStream.Writable {
     const data = arg1 === callback ? undefined : arg1;
     if (data) {
       const encoding = arg2 === callback ? undefined : arg2;
-      this.write(data, encoding, callback);
+      this.write(data, encoding);
     }
     this.writableEnded = true;
     this.writableFinished = true;
     this.emit("close");
     this.emit("finish");
+    if (callback) {
+      callback();
+    }
     return this;
   }
 
diff --git a/test/index.test.ts b/test/index.test.ts
index 23cd3b8..88f0aee 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -112,3 +112,44 @@ describe("fetchNodeRequestHandler", () => {
     });
   });
 });
+
+describe("ServerResponse#end callback", () => {
+  it("invokes callback with no chunk", async () => {
+    const calls: string[] = [];
+    const res = await fetchNodeRequestHandler((_req, res) => {
+      res.on("finish", () => calls.push("finish"));
+      res.end(() => calls.push("callback"));
+    }, "/test");
+    expect(await res.text()).toBe("");
+    expect(calls).toEqual(["finish", "callback"]);
+  });
+
+  it("invokes callback once with chunk", async () => {
+    const calls: string[] = [];
+    const res = await fetchNodeRequestHandler((_req, res) => {
+      res.on("finish", () => calls.push("finish"));
+      res.end("hello", () => calls.push("callback"));
+    }, "/test");
+    expect(await res.text()).toBe("hello");
+    expect(calls).toEqual(["finish", "callback"]);
+  });
+
+  it("invokes callback once with chunk and encoding", async () => {
+    let calls = 0;
+    const res = await fetchNodeRequestHandler((_req, res) => {
+      res.end("hello", "utf8", () => calls++);
+    }, "/test");
+    expect(await res.text()).toBe("hello");
+    expect(calls).toBe(1);
+  });
+
+  it("invokes callback on an already ended response", async () => {
+    let calls = 0;
+    const res = await fetchNodeRequestHandler((_req, res) => {
+      res.end("hello");
+      res.end(() => calls++);
+    }, "/test");
+    expect(await res.text()).toBe("hello");
+    expect(calls).toBe(1);
+  });
+});