Add streaming text support to QRestReply

Provides the possibility to read text data as it arrives, instead
of needing to wait until the whole body is received.

Pick-to: 6.7
Task-number: QTBUG-119002
Change-Id: I64f90148fd41a77c4ae2d5dbd6194a924a9f3a86
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

2 files changed, 26 insertions, 18 deletions

diff --git a/src/network/access/qrestreply.cpp b/src/network/access/qrestreply.cpp
index 0cea26868d..a736660786 100644
--- a/src/network/access/qrestreply.cpp
+++ b/src/network/access/qrestreply.cpp
@@ -222,7 +222,7 @@ QByteArray QRestReply::body()
 }
 
 /*!
-    Returns the received data as a QString. Requires the reply to be finished.
+    Returns the received data as a QString.
 
     The received data is decoded into a QString (UTF-16). The decoding
     uses the \e Content-Type header's \e charset parameter to determine the
@@ -230,33 +230,36 @@ QByteArray QRestReply::body()
     available or not supported by \l QStringConverter, UTF-8 is used as a
     default.
 
-    Calling this function consumes the received data, and any further calls
-    to get response data will return empty.
-
-    This function returns a default-constructed value and will not consume
-    any data if the reply is not finished.
+    Calling this function consumes the data received so far. Returns
+    a default constructed value if no new data is available, or if the
+    decoding is not supported by \l QStringConverter, or if the decoding
+    has errors (for example invalid characters).
 
     \sa json(), body(), isFinished(), finished()
 */
 QString QRestReply::text()
 {
     Q_D(QRestReply);
-    if (!isFinished()) {
-        qCWarning(lcQrest, "Attempt to read text() of an unfinished reply, ignoring.");
-        return {};
-    }
+    QString result;
+
     QByteArray data = d->networkReply->readAll();
     if (data.isEmpty())
+        return result;
+
+    if (!d->decoder) {
+        const QByteArray charset = d->contentCharset();
+        d->decoder = QStringDecoder(charset);
+        if (!d->decoder->isValid()) { // the decoder may not support the mimetype's charset
+            qCWarning(lcQrest, "text(): Charset \"%s\" is not supported", charset.constData());
+            return result;
+        }
+    }
+    // Check if the decoder already had an error, or has errors after decoding current data chunk
+    if (d->decoder->hasError() || (result = (*d->decoder)(data), d->decoder->hasError())) {
+        qCWarning(lcQrest, "text() Decoding error occurred");
         return {};
-
-    const QByteArray charset = d->contentCharset();
-    QStringDecoder decoder(charset);
-    if (!decoder.isValid()) { // the decoder may not support the mimetype's charset
-        qCWarning(lcQrest, "Charset \"%s\" is not supported, defaulting to UTF-8",
-                  charset.constData());
-        decoder = QStringDecoder(QStringDecoder::Utf8);
     }
-    return decoder(data);
+    return result;
 }
 
 /*!
diff --git a/src/network/access/qrestreply_p.h b/src/network/access/qrestreply_p.h
index 4b156b3793..7fe0842ff3 100644
--- a/src/network/access/qrestreply_p.h
+++ b/src/network/access/qrestreply_p.h
@@ -19,8 +19,12 @@
 #include <QtNetwork/qnetworkreply.h>
 #include <QtCore/qjsondocument.h>
 
+#include <optional>
+
 QT_BEGIN_NAMESPACE
 
+class QStringDecoder;
+
 class QRestReplyPrivate : public QObjectPrivate
 {
 public:
@@ -28,6 +32,7 @@ public:
     ~QRestReplyPrivate() override;
 
     QNetworkReply *networkReply = nullptr;
+    std::optional<QStringDecoder> decoder;
 
     QByteArray contentCharset() const;
     bool hasNonHttpError() const;