[memory] Fix provider cannot handle fields with complex characters in name

Fixes #18885

(cherry-picked from 9809f93)

Author: nyalldawson

src/core/providers/memory/qgsmemoryprovider.cpp

@@ -108,7 +108,7 @@ QgsMemoryProvider::QgsMemoryProvider( const QString &uri )
     QStringList fields = url.allQueryItemValues( QStringLiteral( "field" ) );
     for ( int i = 0; i < fields.size(); i++ )
     {
-      QString name = fields.at( i );
+      QString name = QUrl::fromPercentEncoding( fields.at( i ).toUtf8() );
       QVariant::Type type = QVariant::String;
       QVariant::Type subType = QVariant::Invalid;
       QString typeName( QStringLiteral( "string" ) );

src/core/providers/memory/qgsmemoryproviderutils.cpp

@@ -72,7 +72,7 @@ QgsVectorLayer *QgsMemoryProviderUtils::createMemoryLayer( const QString &name,
     {
       lengthPrecision = QStringLiteral( "(%1)" ).arg( field.length() );
     }
-    parts << QStringLiteral( "field=%1:%2%3" ).arg( field.name(), memoryLayerFieldType( field.type() ), lengthPrecision );
+    parts << QStringLiteral( "field=%1:%2%3" ).arg( QString( QUrl::toPercentEncoding( field.name() ) ), memoryLayerFieldType( field.type() ), lengthPrecision );
   }
 
   QString uri = geomType + '?' + parts.join( '&' );

tests/src/python/test_provider_memory.py

@@ -275,6 +275,16 @@ def testLengthPrecisionFromUri(self):
         self.assertEqual(myMemoryLayer.fields().field('size').length(), 12)
         self.assertEqual(myMemoryLayer.fields().field('size').precision(), 9)
 
+    def testFromUriWithEncodedField(self):
+        """Test we can construct the mem provider from a uri when a field name is encoded"""
+        layer = QgsVectorLayer(
+            ('Point?crs=epsg:4326&field=name:string(20)&'
+             'field=test%2Ffield:integer'),
+            'test',
+            'memory')
+        self.assertTrue(layer.isValid())
+        self.assertEqual([f.name() for f in layer.fields()], ['name', 'test/field'])
+
     def testSaveFields(self):
         # Create a new memory layer with no fields
         myMemoryLayer = QgsVectorLayer(
@@ -398,6 +408,8 @@ def testCreateMemoryLayer(self):
         fields.append(QgsField("date", QVariant.Date))
         fields.append(QgsField("datetime", QVariant.DateTime))
         fields.append(QgsField("time", QVariant.Time))
+        fields.append(QgsField("#complex_name", QVariant.String))
+        fields.append(QgsField("complex/name", QVariant.String))
         layer = QgsMemoryProviderUtils.createMemoryLayer('my name', fields)
         self.assertTrue(layer.isValid())
         self.assertFalse(layer.fields().isEmpty())