[ogr] fix JSON array interpreted as QVariantMap

Fix #61728

src/core/providers/ogr/qgsogrprovider.cpp

@@ -886,9 +886,9 @@ void QgsOgrProvider::loadFields()
   QMutexLocker locker( datasetMutex );
 #endif
 
-  for ( int i = 0; i < fdef.GetFieldCount(); ++i )
+  for ( int fieldIndex = 0; fieldIndex < fdef.GetFieldCount(); ++fieldIndex )
   {
-    OGRFieldDefnH fldDef = fdef.GetFieldDefn( i );
+    OGRFieldDefnH fldDef = fdef.GetFieldDefn( fieldIndex );
     const OGRFieldType ogrType = OGR_Fld_GetType( fldDef );
     const OGRFieldSubType ogrSubType = OGR_Fld_GetSubType( fldDef );
 
@@ -896,6 +896,38 @@ void QgsOgrProvider::loadFields()
     QMetaType::Type varSubType = QMetaType::Type::UnknownType;
     QgsOgrUtils::ogrFieldTypeToQVariantType( ogrType, ogrSubType, varType, varSubType );
 
+    // Handle special case for OGRFieldType::OFSTJSON which is not always a map.
+    // If subtype is JSON and varType is map, try to load a feature and check if it's
+    // really an object (rather than something else like an array)
+    // fallback to string given that only JSON object (map) is supported.
+    if ( varType == QMetaType::Type::QVariantMap && ogrSubType == OFSTJSON )
+    {
+      QRecursiveMutex *layerMutex = nullptr;
+      OGRLayerH ogrLayer = mOgrLayer->getHandleAndMutex( layerMutex );
+      QMutexLocker layerLocker( layerMutex );
+      gdal::ogr_feature_unique_ptr f( OGR_L_GetNextFeature( ogrLayer ) );
+      if ( f )
+      {
+        const char *json = OGR_F_GetFieldAsString( f.get(), fieldIndex );
+        if ( json && json[0] != '\0' )
+        {
+          try
+          {
+            const auto json_element = json::parse( json );
+            if ( ! json_element.is_object() )
+            {
+              varType = QMetaType::Type::QString;
+            }
+          }
+          catch ( const json::parse_error & )
+          {
+            varType = QMetaType::Type::QString;
+          }
+        }
+        OGR_L_ResetReading( ogrLayer );
+      }
+    }
+
     //TODO: fix this hack
 #ifdef ANDROID
     QString name = OGR_Fld_GetNameRef( fldDef );

src/core/qgsogrutils.cpp

@@ -1862,7 +1862,6 @@ void QgsOgrUtils::ogrFieldTypeToQVariantType( OGRFieldType ogrType, OGRFieldSubT
     case OFTWideString:
       if ( ogrSubType == OFSTJSON )
       {
-        ogrSubType = OFSTJSON;
         variantType = QMetaType::Type::QVariantMap;
         variantSubType = QMetaType::Type::QString;
       }

tests/src/core/testqgsogrprovider.cpp

@@ -58,6 +58,8 @@ class TestQgsOgrProvider : public QgsTest
     void testExtent();
     void testVsiCredentialOptions();
     void testVsiCredentialOptionsQuerySublayers();
+    void testJSONFields_data();
+    void testJSONFields();
 
   private:
     QString mTestDataDir;
@@ -579,5 +581,168 @@ void TestQgsOgrProvider::testVsiCredentialOptionsQuerySublayers()
 }
 
 
+void TestQgsOgrProvider::testJSONFields_data()
+{
+  QTest::addColumn<QString>( "jsonData" );
+  QTest::addColumn<int>( "expectedType" );
+
+  QTest::newRow( "array of map" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "array_of_map": [
+          {
+            "a": 1,
+            "b": 2.0
+          }
+        ]
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QString );
+
+  QTest::newRow( "map" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "map": {
+          "a": 1,
+          "b": 2.0
+        }
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QVariantMap );
+
+  QTest::newRow( "int" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "int": 1
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::Int );
+
+  QTest::newRow( "stringlist" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "string_list": [ "a", "b", "c" ]
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QStringList );
+
+  QTest::newRow( "string" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "string": "a"
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QString );
+
+  QTest::newRow( "double" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "double": 1.0
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::Double );
+
+  QTest::newRow( "bool" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "bool": true
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::Bool );
+
+  QTest::newRow( "int list" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "int_list": [1, 2, 3]
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QVariantList );
+
+  QTest::newRow( "real list" ) << QStringLiteral( R"json(
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": {
+        "real_list": [1.0, 2.1, 3]
+      }
+    }
+  ]
+}
+)json" ) << static_cast<int>( QMetaType::Type::QVariantList );
+}
+
+void TestQgsOgrProvider::testJSONFields()
+{
+  QFETCH( QString, jsonData );
+  QFETCH( int, expectedType );
+
+  QTemporaryDir dir;
+  QString filePath = dir.path() + "/test.json";
+  QFile file( filePath );
+  if ( file.open( QIODevice::WriteOnly ) )
+  {
+    QTextStream textStream( &file );
+    textStream << jsonData;
+    file.close();
+  }
+  QgsVectorLayer layer { filePath, QStringLiteral( "json" ), QLatin1String( "ogr" ) };
+  QVERIFY( layer.isValid() );
+  QgsFields fields = layer.fields();
+  QCOMPARE( fields.count(), 1 );
+  QgsField field = fields.at( 0 );
+  QCOMPARE( static_cast<int>( field.type() ), expectedType );
+}
+
+
 QGSTEST_MAIN( TestQgsOgrProvider )
 #include "testqgsogrprovider.moc"