[gpkg] Add test for gpkg subsetstring don't unlock mutex twice

I wanted to add the test for gpkg subsetstring even if
it was not bugged, while testing that, I hit an assert
in Qt core that pointed me to double unlocked locks.

src/providers/ogr/qgsogrprovider.cpp

@@ -5258,7 +5258,6 @@ QGISEXTERN bool saveStyle( const QString &uri, const QString &qmlStyle, const QS
     if ( !hLayer )
     {
       errCause = QObject::tr( "Unable to save layer style. It's not possible to create the destination table on the database." );
-      mutex->unlock();
       return false;
     }
     bool ok = true;
@@ -5322,7 +5321,6 @@ QGISEXTERN bool saveStyle( const QString &uri, const QString &qmlStyle, const QS
     if ( !ok )
     {
       errCause = QObject::tr( "Unable to save layer style. It's not possible to create the destination table on the database." );
-      mutex->unlock();
       return false;
     }
   }
@@ -5379,7 +5377,6 @@ QGISEXTERN bool saveStyle( const QString &uri, const QString &qmlStyle, const QS
                                   QMessageBox::Yes | QMessageBox::No ) == QMessageBox::No ) )
     {
       errCause = QObject::tr( "Operation aborted" );
-      mutex->unlock();
       return false;
     }
     bNew = false;
@@ -5431,8 +5428,6 @@ QGISEXTERN bool saveStyle( const QString &uri, const QString &qmlStyle, const QS
   else
     bFeatureOK = OGR_L_SetFeature( hLayer, hFeature.get() ) == OGRERR_NONE;
 
-  mutex->unlock();
-
   if ( !bFeatureOK )
   {
     QgsMessageLog::logMessage( QObject::tr( "Error updating style" ) );

tests/src/python/test_provider_ogr_gpkg.py

@@ -13,6 +13,7 @@
 __revision__ = '$Format:%H$'
 
 import os
+import re
 import shutil
 import sys
 import tempfile
@@ -860,6 +861,42 @@ def testSubSetStringEditable_bug17795(self):
         vl.setSubsetString('')
         self.assertTrue(vl.dataProvider().capabilities() & isEditable)
 
+    def testSubsetStringExtent_bug17863(self):
+        """Check that the extent is correct when applied in the ctor and when
+        modified after a subset string is set """
+
+        def _lessdigits(s):
+            return re.sub(r'(\d+\.\d{3})\d+', r'\1', s)
+
+        testPath = TEST_DATA_DIR + '/' + 'provider/bug_17795.gpkg|layername=bug_17795'
+        subSetString = '"name" = \'int\''
+        subSet = '|layername=bug_17795|subset=%s' % subSetString
+
+        # unfiltered
+        vl = QgsVectorLayer(testPath, 'test', 'ogr')
+        self.assertTrue(vl.isValid())
+        unfiltered_extent = _lessdigits(vl.extent().toString())
+        del(vl)
+
+        # filter after construction ...
+        subSet_vl2 = QgsVectorLayer(testPath, 'test', 'ogr')
+        self.assertEqual(_lessdigits(subSet_vl2.extent().toString()), unfiltered_extent)
+        # ... apply filter now!
+        subSet_vl2.setSubsetString(subSetString)
+        self.assertEqual(subSet_vl2.subsetString(), subSetString)
+        self.assertNotEqual(_lessdigits(subSet_vl2.extent().toString()), unfiltered_extent)
+        filtered_extent = _lessdigits(subSet_vl2.extent().toString())
+        del(subSet_vl2)
+
+        # filtered in constructor
+        subSet_vl = QgsVectorLayer(testPath + subSet, 'subset_test', 'ogr')
+        self.assertEqual(subSet_vl.subsetString(), subSetString)
+        self.assertTrue(subSet_vl.isValid())
+
+        # This was failing in bug 17863
+        self.assertEqual(_lessdigits(subSet_vl.extent().toString()), filtered_extent)
+        self.assertNotEqual(_lessdigits(subSet_vl.extent().toString()), unfiltered_extent)
+
 
 if __name__ == '__main__':
     unittest.main()