QgsRelation::generateId(): fix crash on empty QgsRelation object

qgis · Jan 27, 2021 · d222e3b · d222e3b
1 parent 5084507
commit d222e3b
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Showing 2 changed files with 14 additions and 5 deletions.
diff --git a/src/core/qgsrelation.cpp b/src/core/qgsrelation.cpp
@@ -261,11 +261,15 @@ QString QgsRelation::id() const
 
 void QgsRelation::generateId()
 {
-  d->mRelationId = QStringLiteral( "%1_%2_%3_%4" )
-                   .arg( referencingLayerId(),
-                         d->mFieldPairs.at( 0 ).referencingField(),
-                         referencedLayerId(),
-                         d->mFieldPairs.at( 0 ).referencedField() );
+  if ( !d->mFieldPairs.isEmpty() )
+  {
+    const QgsRelation::FieldPair fieldPair = d->mFieldPairs.at( 0 );
+    d->mRelationId = QStringLiteral( "%1_%2_%3_%4" )
+                     .arg( referencingLayerId(),
+                           fieldPair.referencingField(),
+                           referencedLayerId(),
+                           fieldPair.referencedField() );
+  }
   updateRelationStatus();
 }
 

diff --git a/tests/src/python/test_qgsrelation.py b/tests/src/python/test_qgsrelation.py
@@ -197,6 +197,11 @@ def testValidRelationAfterChangingStyle(self):
                     valid = t.relation().isValid()
         self.assertTrue(valid)
 
+    def test_generateId_empty_relation(self):
+        rel = QgsRelation()
+        # Check that it does not crash
+        rel.generateId()
+
 
 if __name__ == '__main__':
     unittest.main()