Fix crash when writing CRS to XML using QgsXmlUtils

Fixes a crash when saving a processing model using a CRS input

Author: nyalldawson

src/core/qgsapplication.cpp

@@ -199,6 +199,7 @@ void QgsApplication::init( QString profileFolder )
   qRegisterMetaType<QgsReferencedPointXY>( "QgsReferencedPointXY" );
   qRegisterMetaType<QgsLayoutRenderContext::Flags>( "QgsLayoutRenderContext::Flags" );
   qRegisterMetaType<QgsStyle::StyleEntity>( "QgsStyle::StyleEntity" );
+  qRegisterMetaType<QgsCoordinateReferenceSystem>( "QgsCoordinateReferenceSystem" );
 
   QString prefixPath( getenv( "QGIS_PREFIX_PATH" ) ? getenv( "QGIS_PREFIX_PATH" ) : applicationDirPath() );
   // QgsDebugMsg( QString( "prefixPath(): %1" ).arg( prefixPath ) );

src/core/qgsxmlutils.cpp

@@ -168,6 +168,13 @@ QDomElement QgsXmlUtils::writeVariant( const QVariant &value, QDomDocument &doc
         element.appendChild( propertyElem );
         break;
       }
+      else if ( value.canConvert< QgsCoordinateReferenceSystem >() )
+      {
+        element.setAttribute( QStringLiteral( "type" ), QStringLiteral( "QgsCoordinateReferenceSystem" ) );
+        const QgsCoordinateReferenceSystem crs = value.value< QgsCoordinateReferenceSystem >();
+        crs.writeXml( element, doc );
+        break;
+      }
       FALLTHROUGH
     }
 
@@ -250,6 +257,12 @@ QVariant QgsXmlUtils::readVariant( const QDomElement &element )
 
     return QVariant();
   }
+  else if ( type == QLatin1String( "QgsCoordinateReferenceSystem" ) )
+  {
+    QgsCoordinateReferenceSystem crs;
+    crs.readXml( element );
+    return crs;
+  }
   else
   {
     return QVariant();

tests/src/python/test_qgsxmlutils.py

@@ -15,13 +15,13 @@
 import qgis  # NOQA switch sip api
 
 from qgis.core import (QgsXmlUtils,
-                       QgsProperty)
+                       QgsProperty,
+                       QgsCoordinateReferenceSystem)
 
 from qgis.PyQt.QtXml import QDomDocument
 
 from qgis.testing import start_app, unittest
 
-
 start_app()
 
 
@@ -141,6 +141,25 @@ def test_property(self):
 
         self.assertEqual(prop, prop2)
 
+    def test_crs(self):
+        """
+        Test that QgsCoordinateReferenceSystem values are correctly loaded and written
+        """
+        doc = QDomDocument("properties")
+
+        crs = QgsCoordinateReferenceSystem('epsg:3111')
+        elem = QgsXmlUtils.writeVariant(crs, doc)
+
+        crs2 = QgsXmlUtils.readVariant(elem)
+        self.assertTrue(crs2.isValid())
+        self.assertEqual(crs2.authid(), 'EPSG:3111')
+
+        crs = QgsCoordinateReferenceSystem()
+        elem = QgsXmlUtils.writeVariant(crs, doc)
+
+        crs2 = QgsXmlUtils.readVariant(elem)
+        self.assertFalse(crs2.isValid())
+
 
 if __name__ == '__main__':
     unittest.main()