QGrpcHttp2Channel: implement filterServerMetadata option

Implement the filtering of internal and reserved keys for the server
metadata. gRPC over HTTP2 responses are well defined and such
information shouldn't be provided to users. At least not by default.

Ref: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#responses

This patch changes the filtering to be applied by default.

[ChangeLog][QGrpcHttp2Channel/QGrpcOperation][Important Behavior Changes]
QGrpcOperation::serverInitialMetadata() and
QGrpcOperation::serverTrailingMetadata() no longer include any internal
gRPC or HTTP/2 pseudo‑headers by default.

Fixes: QTBUG-138363
Change-Id: I4af9e8abe60799e817f47faa5de4c2d0e41854be
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

src/grpc/qgrpchttp2channel.cpp

@@ -68,6 +68,8 @@ using namespace QtGrpc;
     {serializationFormat}, or other options by constructing it with a
     QGrpcChannelOptions containing the required customizations.
 
+    \note \l{QGrpcChannelOptions::filterServerMetadata} is enabled by default.
+
     \section2 Transportation scheme
 
     The QGrpcHttp2Channel implementation prefers different transportation
@@ -312,6 +314,7 @@ public:
 
 private:
     [[nodiscard]] HPack::HttpHeader constructInitialHeaders() const;
+    [[nodiscard]] bool constructFilterServerMetadata() const;
     [[nodiscard]] QGrpcHttp2ChannelPrivate *channelPriv() const;
     [[nodiscard]] QGrpcHttp2Channel *channel() const;
     [[nodiscard]] bool handleContextExpired();
@@ -324,6 +327,7 @@ private:
     State m_state = State::Idle;
     const bool m_endStreamAtFirstData;
     bool m_writesDoneSent = false;
+    bool m_filterServerMetadata;
     QTimer m_deadlineTimer;
 
     Q_DISABLE_COPY_MOVE(Http2Handler)
@@ -434,7 +438,7 @@ private:
 Http2Handler::Http2Handler(QGrpcOperationContext *operation, QGrpcHttp2ChannelPrivate *parent,
                            bool endStream)
     : QObject(parent), m_operation(operation), m_initialHeaders(constructInitialHeaders()),
-      m_endStreamAtFirstData(endStream)
+      m_endStreamAtFirstData(endStream), m_filterServerMetadata(constructFilterServerMetadata())
 {
     // If the context (lifetime bound to the user) is destroyed, this handler
     // can no longer perform any meaningful work. We allow it to be deleted;
@@ -598,6 +602,13 @@ HPack::HttpHeader Http2Handler::constructInitialHeaders() const
     return headers;
 }
 
+bool Http2Handler::constructFilterServerMetadata() const
+{
+    return m_operation->callOptions()
+        .filterServerMetadata()
+        .value_or(channel()->channelOptions().filterServerMetadata().value_or(true));
+}
+
 QGrpcHttp2ChannelPrivate *Http2Handler::channelPriv() const
 {
     return qobject_cast<QGrpcHttp2ChannelPrivate *>(this->parent());
@@ -815,9 +826,13 @@ void Http2Handler::handleHeaders(const HPack::HttpHeader &headers, HeaderPhase p
             qGrpcWarning("Received unexcpected gRPC-reserved header: { key: %s, value: %s } in "
                          "phase: %s",
                          k.data(), v.data(), QDebug::toBytes(phase).data());
+        } else { // Custom-Metadata
+            metadata.insert(k, v);
+            continue;
         }
 
-        metadata.insert(k, v);
+        if (!m_filterServerMetadata)
+            metadata.insert(k, v);
     }
 
     if (validation.requireHttpStatus && !validation.hasHttpStatus) {

tests/auto/grpc/client/unarycall/tst_grpc_client_unarycall.cpp

@@ -47,6 +47,7 @@ private Q_SLOTS:
 #if QT_DEPRECATED_SINCE(6, 13)
     void deprecatedMetadata();
 #endif
+    void metadata_data();
     void metadata();
 };
 
@@ -171,8 +172,17 @@ void QtGrpcClientUnaryCallTest::deprecatedMetadata()
 
 #endif // QT_DEPRECATED_SINCE(6, 13)
 
+void QtGrpcClientUnaryCallTest::metadata_data()
+{
+    QTest::addColumn<bool>("filterServerMetadata");
+    QTest::addRow("filterServerMetadata(true)") << true;
+    QTest::addRow("filterServerMetadata(false)") << false;
+}
+
 void QtGrpcClientUnaryCallTest::metadata()
 {
+    // TODO: QTBUG-138407
+    QFETCH(const bool, filterServerMetadata);
     QGrpcCallOptions opt;
     QMultiHash<QByteArray, QByteArray> clientMd{
         { "request_initial",  "3"  },
@@ -180,6 +190,7 @@ void QtGrpcClientUnaryCallTest::metadata()
         { "request_sum",      "20" },
         { "request_sum",      "10" }
     };
+    opt.setFilterServerMetadata(filterServerMetadata);
     opt.setMetadata(clientMd);
     auto reply = client()->testMetadata({}, opt);
     QSignalSpy replyFinishedSpy(reply.get(), &QGrpcCallReply::finished);
@@ -191,6 +202,10 @@ void QtGrpcClientUnaryCallTest::metadata()
     QVERIFY(args.first().value<QGrpcStatus>().isOk());
 
     const auto &initialMd = reply->serverInitialMetadata();
+    if (filterServerMetadata)
+        QCOMPARE_EQ(initialMd.size(), 3);
+    else
+        QCOMPARE_GT(initialMd.size(), 3);
     auto initialIt = initialMd.equal_range("response_initial");
     QCOMPARE_EQ(std::distance(initialIt.first, initialIt.second), 3);
     QCOMPARE_EQ(initialIt.first.value(), "2");
@@ -200,6 +215,10 @@ void QtGrpcClientUnaryCallTest::metadata()
     QCOMPARE_EQ(initialIt.first.value(), "0");
 
     const auto &trailingMd = reply->serverTrailingMetadata();
+    if (filterServerMetadata)
+        QCOMPARE_EQ(trailingMd.size(), 3);
+    else
+        QCOMPARE_GT(trailingMd.size(), 3);
     auto trailingIt = trailingMd.equal_range("response_trailing");
     QCOMPARE_EQ(std::distance(trailingIt.first, trailingIt.second), 2);
     QCOMPARE_EQ(trailingIt.first.value(), "1");