From 22e8fa9b7060baf50a2f3177c960dc393cd7e580 Mon Sep 17 00:00:00 2001
From: andrewlalis <andrewlalisofficial@gmail.com>
Date: Sun, 27 Jul 2025 11:14:24 -0400
Subject: [PATCH] Fixed flushing of empty responses.

---
 source/handy_http_transport/http1/task_pool.d |  8 +++++++-
 source/handy_http_transport/http1/transport.d | 19 ++++++++++++++-----
 .../response_output_stream.d                  | 18 ++++++++++++++++--
 3 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/source/handy_http_transport/http1/task_pool.d b/source/handy_http_transport/http1/task_pool.d
index 6050cc9..92769b7 100644
--- a/source/handy_http_transport/http1/task_pool.d
+++ b/source/handy_http_transport/http1/task_pool.d
@@ -56,7 +56,13 @@ unittest {
     HttpRequestHandler handler = HttpRequestHandler.of(
         (ref ServerHttpRequest request, ref ServerHttpResponse response) {
             response.status = HttpStatus.OK;
-            response.writeBodyString("Testing");
         });
     testHttp1Transport(new TaskPoolHttp1Transport(handler));
+
+    HttpRequestHandler handler2 = HttpRequestHandler.of(
+        (ref ServerHttpRequest request, ref ServerHttpResponse response) {
+            response.status = HttpStatus.OK;
+            response.writeBodyString("Testing");
+        });
+    testHttp1Transport(new TaskPoolHttp1Transport(handler2));
 }
diff --git a/source/handy_http_transport/http1/transport.d b/source/handy_http_transport/http1/transport.d
index 79d25ce..e57edde 100644
--- a/source/handy_http_transport/http1/transport.d
+++ b/source/handy_http_transport/http1/transport.d
@@ -87,7 +87,7 @@ version(unittest) {
          
         string httpResponseContent = cast(string) buffer[0 .. totalBytesReceived];
         string[] parts = httpResponseContent.split("\r\n\r\n");
-        assert(parts.length > 0, "HTTP 1.1 response is missing required status and headers section.");
+        assert(parts.length > 0, "HTTP 1.1 response is missing required status and headers section:\n\n" ~ httpResponseContent);
         string[] headerLines = parts[0].split("\r\n");
         assert(headerLines.length > 0, "HTTP 1.1 response is missing required status line.");
         string statusLine = headerLines[0];
@@ -131,13 +131,22 @@ void handleClient(Socket clientSocket, HttpRequestHandler requestHandler) {
     scope ServerHttpRequest request = result.request;
     scope ServerHttpResponse response;
     SocketOutputStream* outputStream = new SocketOutputStream(clientSocket);
-    response.outputStream = outputStreamObjectFor(HttpResponseOutputStream!(SocketOutputStream*)(
-        outputStream,
-        &response
-    ));
+    HttpResponseOutputStream!(SocketOutputStream*) responseOutputStream
+        = HttpResponseOutputStream!(SocketOutputStream*)(
+            outputStream,
+            &response
+        );
+    response.outputStream = outputStreamObjectFor(&responseOutputStream);
     try {
         requestHandler.handle(request, response);
         debugF!"%s %s -> %d %s"(request.method, request.url, response.status.code, response.status.text);
+        // If the response's headers aren't flushed yet, write them now.
+        if (!responseOutputStream.areHeadersFlushed()) {
+            auto writeResult = responseOutputStream.writeHeaders();
+            if (writeResult.hasError) {
+                errorF!"Failed to write response headers: %s"(writeResult.error.message);
+            }
+        }
     } catch (Exception e) {
         error("Exception thrown while handling request.", e);
     } catch (Throwable t) {
diff --git a/source/handy_http_transport/response_output_stream.d b/source/handy_http_transport/response_output_stream.d
index ac302e4..3fee831 100644
--- a/source/handy_http_transport/response_output_stream.d
+++ b/source/handy_http_transport/response_output_stream.d
@@ -23,6 +23,15 @@ struct HttpResponseOutputStream(S) if (isByteOutputStream!S) {
         this.response = response;
     }
 
+    /**
+     * Determines if the HTTP response headers have been flushed to the
+     * underlying output stream.
+     * Returns: `true` if the headers have been flushed, `false` otherwise.
+     */
+    bool areHeadersFlushed() const {
+        return headersFlushed;
+    }
+
     /**
      * Writes the given data to the stream. If the referenced HTTP response's
      * status and headers haven't yet been written, they will be written first.
@@ -37,7 +46,6 @@ struct HttpResponseOutputStream(S) if (isByteOutputStream!S) {
             auto result = writeHeaders();
             if (result.hasError) return result;
             bytesWritten += result.count;
-            headersFlushed = true;
         }
         auto result = outputStream.writeToStream(buffer);
         if (result.hasError) return result;
@@ -50,6 +58,10 @@ struct HttpResponseOutputStream(S) if (isByteOutputStream!S) {
      * Returns: The stream result of writing.
      */
     StreamResult writeHeaders() {
+        if (headersFlushed) {
+            return StreamResult(0); // No need to write again.
+        }
+        headersFlushed = true;
         size_t idx = 0;
         char[6] statusCodeBuffer; // Normal HTTP codes are 3 digits, but this leaves room for extensions.
         writeUIntToBuffer(response.status.code, statusCodeBuffer, idx);
@@ -111,13 +123,15 @@ unittest {
     resp.status = HttpStatus.OK;
     resp.headers.add("Content-Type", "text/plain");
     auto httpOut = HttpResponseOutputStream!(ArrayOutputStream!ubyte*)(&os, &resp);
-    resp.outputStream = outputStreamObjectFor(httpOut);
+    resp.outputStream = outputStreamObjectFor(&httpOut);
+    assert(httpOut.areHeadersFlushed() == false);
     StreamResult r = resp.outputStream.writeToStream(cast(ubyte[]) "Hello world!");
     const expectedOutput =
         "HTTP/1.1 200 OK\r\n" ~
         "Content-Type: text/plain\r\n" ~
         "\r\n" ~
         "Hello world!";
+    assert(httpOut.areHeadersFlushed() == true);
     assert(os.toArray() == expectedOutput);
     assert(r.hasCount);
     assert(r.count == os.toArray().length);