From 46bce56bfb1e98033c4fe954a3be2f8b661e00c0 Mon Sep 17 00:00:00 2001
From: Dennis Oberst <dennis.oberst@qt.io>
Date: Fri, 18 Jul 2025 16:13:31 +0200
Subject: [PATCH] Http2Handler: construct initial headers in initialization
 list

This patch follows C++ best practices. Refactor the
'prepareInitialRequest' function to directly return the constructed
headers so that we can use them in the initializer list.

Ref: https://isocpp.org/wiki/faq/ctors#init-lists

Pick-to: 6.10 6.9 6.8
Change-Id: I095d9ecc3574b8ad1ed344d16701102d2c79df92
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
---
 src/grpc/qgrpchttp2channel.cpp | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/grpc/qgrpchttp2channel.cpp b/src/grpc/qgrpchttp2channel.cpp
index d3382ae7..2043205e 100644
--- a/src/grpc/qgrpchttp2channel.cpp
+++ b/src/grpc/qgrpchttp2channel.cpp
@@ -271,13 +271,12 @@ public:
     void deadlineTimeout();
 
 private:
-    void prepareInitialRequest(QGrpcOperationContext *operationContext,
-                               QGrpcHttp2ChannelPrivate *channel);
+    [[nodiscard]] HPack::HttpHeader constructInitialHeaders() const;
     [[nodiscard]] QGrpcHttp2ChannelPrivate *channelPriv() const;
     [[nodiscard]] QGrpcHttp2Channel *channel() const;
 
-    HPack::HttpHeader m_initialHeaders;
     std::weak_ptr<QGrpcOperationContext> m_operation;
+    HPack::HttpHeader m_initialHeaders;
     QQueue<QByteArray> m_queue;
     QPointer<QHttp2Stream> m_stream;
     ExpectedData m_expectedData;
@@ -378,7 +377,8 @@ private:
 
 Http2Handler::Http2Handler(const std::shared_ptr<QGrpcOperationContext> &operation,
                            QGrpcHttp2ChannelPrivate *parent, bool endStream)
-    : QObject(parent), m_operation(operation), m_endStreamAtFirstData(endStream)
+    : QObject(parent), m_operation(operation), m_initialHeaders(constructInitialHeaders()),
+      m_endStreamAtFirstData(endStream)
 {
     auto *channelOpPtr = operation.get();
     QObject::connect(channelOpPtr, &QGrpcOperationContext::cancelRequested, this,
@@ -391,7 +391,8 @@ Http2Handler::Http2Handler(const std::shared_ptr<QGrpcOperationContext> &operati
     }
     QObject::connect(channelOpPtr, &QGrpcOperationContext::finished, &m_deadlineTimer,
                      &QTimer::stop);
-    prepareInitialRequest(channelOpPtr, parent);
+
+    writeMessage(channelOpPtr->argument());
 }
 
 Http2Handler::~Http2Handler()
@@ -506,10 +507,9 @@ QGrpcOperationContext *Http2Handler::operation() const
     return m_operation.lock().get();
 }
 
-// Prepares the initial headers and enqueues the initial message.
+// Builds HTTP/2 headers for the initial gRPC request.
 // The headers are sent once the HTTP/2 connection is established.
-void Http2Handler::prepareInitialRequest(QGrpcOperationContext *operationContext,
-                                         QGrpcHttp2ChannelPrivate *channel)
+HPack::HttpHeader Http2Handler::constructInitialHeaders() const
 {
     const static QByteArray AuthorityHeader(":authority");
     const static QByteArray MethodHeader(":method");
@@ -527,10 +527,13 @@ void Http2Handler::prepareInitialRequest(QGrpcOperationContext *operationContext
                                     + QSysInfo::productType().toUtf8() + '/'
                                     + QSysInfo::productVersion().toUtf8() + ')');
 
-    const auto &channelOptions = channel->q_ptr->channelOptions();
+    const auto &channelOptions = channel()->channelOptions();
+    const auto *operationContext = operation();
+    const auto *channel = channelPriv();
+
     QByteArray service{ operationContext->service() };
     QByteArray method{ operationContext->method() };
-    m_initialHeaders = HPack::HttpHeader{
+    auto headers = HPack::HttpHeader{
         { AuthorityHeader,          channel->authorityHeader()               },
         { MethodHeader,             MethodValue                              },
         { PathHeader,               QByteArray('/' + service + '/' + method) },
@@ -542,21 +545,21 @@ void Http2Handler::prepareInitialRequest(QGrpcOperationContext *operationContext
         { TEHeader,                 TEValue                                  },
     };
 
-    auto iterateMetadata = [this](const auto &metadata) {
+    auto iterateMetadata = [&headers](const auto &metadata) {
         for (const auto &[key, value] : metadata.asKeyValueRange()) {
             const auto lowerKey = key.toLower();
             if (lowerKey == AuthorityHeader || lowerKey == MethodHeader || lowerKey == PathHeader
                 || lowerKey == SchemeHeader || lowerKey == ContentTypeHeader) {
                 continue;
             }
-            m_initialHeaders.emplace_back(lowerKey, value);
+            headers.emplace_back(lowerKey, value);
         }
     };
 
     iterateMetadata(channelOptions.metadata(QtGrpc::MultiValue));
     iterateMetadata(operationContext->callOptions().metadata(QtGrpc::MultiValue));
 
-    writeMessage(operationContext->argument());
+    return headers;
 }
 
 QGrpcHttp2ChannelPrivate *Http2Handler::channelPriv() const