Fix conversions to JSON from QVariant

After reimplementing Qt JSON support on top of CBOR, there were
unintended behavior changes when converting QVariant{, List, Map} to
QJson{Value, Array, List} due to reusing the code for converting
QVariant* types to CBOR types, and from CBOR types to corresponding JSON
types. In particular, conversions from QVariant containing QByteArray to
JSON has been affected: according to RFC 7049, when converting from
CBOR to JSON, raw byte array data must be encoded in base64url when
converting to a JSON string. As a result QVariant* types containing
QByteArray data ended up base64url-encoded when converted to JSON,
instead of converting using QString::fromUtf8() as before.

There were also differences when converting QRegularExpression.

Reverted the behavior changes by adding a flag to internal methods for
converting CBOR to JSON, to distinguish whether the conversion is done
from QVariant* or CBOR types. These methods now will fall back to the old
behavior, if the conversion is done using QJson*::fromVariant*().

Additionally fixed QJsonValue::fromVariant conversion for NaN and
infinities: they should always convert to QJsonValue::Null. This works
correctly when converting from variant to QJsonArray/QJsonObject, but has
been wrong for QJsonValue.

Added more tests to verify the expected behavior.

[ChangeLog][Important Behavior Changes] Restored pre-5.15.0 behavior
when converting from QVariant* to QJson* types. Unforeseen consequences
of changes in 5.15.0 caused QByteArray data to be base64url-encoded; the
handling of QRegularExpression was also unintentionally changed. These
conversions are now reverted to the prior behavior. Additionally fixed
QJsonValue::fromVariant conversions for NaN and infinities: they should
always convert to QJsonValue::Null.

Fixes: QTBUG-84739
Change-Id: Iaee667d00e5363906eedbb67948b7b39c9d0bc78
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/corelib/serialization/qjson_p.h b/src/corelib/serialization/qjson_p.h
index 4589284ef3..b6f01bff1c 100644
--- a/src/corelib/serialization/qjson_p.h
+++ b/src/corelib/serialization/qjson_p.h
@@ -215,6 +215,13 @@ public:
     }
 };
 
+class Variant
+{
+public:
+    static QJsonObject toJsonObject(const QVariantMap &map);
+    static QJsonArray toJsonArray(const QVariantList &list);
+};
+
 } // namespace QJsonPrivate
 
 QT_END_NAMESPACE