[expression] Fix eval_template() not working with field caltulator an…

…d virtual fields
qgis · Aug 27, 2024 · 489b66c · 489b66c
1 parent 450966f
commit 489b66c
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Showing 2 changed files with 39 additions and 1 deletion.
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -9148,7 +9148,28 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
     functions
         << varFunction;
 
-    functions << new QgsStaticExpressionFunction( QStringLiteral( "eval_template" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "template" ) ), fcnEvalTemplate, QStringLiteral( "General" ), QString(), true );
+    QgsStaticExpressionFunction *evalTemplateFunction = new QgsStaticExpressionFunction( QStringLiteral( "eval_template" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "template" ) ), fcnEvalTemplate, QStringLiteral( "General" ), QString(), true, QSet<QString>() << QgsFeatureRequest::ALL_ATTRIBUTES );
+    evalTemplateFunction->setIsStaticFunction(
+      []( const QgsExpressionNodeFunction * node, QgsExpression * parent, const QgsExpressionContext * context )
+    {
+      if ( node->args()->count() > 0 )
+      {
+        QgsExpressionNode *argNode = node->args()->at( 0 );
+
+        if ( argNode->isStatic( parent, context ) )
+        {
+          QString expString = argNode->eval( parent, context ).toString();
+
+          QgsExpression e( expString );
+
+          if ( e.rootNode() && e.rootNode()->isStatic( parent, context ) )
+            return true;
+        }
+      }
+
+      return false;
+    } );
+    functions << evalTemplateFunction;
 
     QgsStaticExpressionFunction *evalFunc = new QgsStaticExpressionFunction( QStringLiteral( "eval" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "expression" ) ), fcnEval, QStringLiteral( "General" ), QString(), true, QSet<QString>() << QgsFeatureRequest::ALL_ATTRIBUTES );
     evalFunc->setIsStaticFunction(

diff --git a/tests/src/python/test_qgsexpression.py b/tests/src/python/test_qgsexpression.py
@@ -323,6 +323,23 @@ def testSuccessfulEvaluationReturnsNoEvalErrorString(self):
         exp = QgsExpression("True is False")  # the result does not matter
         self.assertEqual(exp.evalErrorString(), "")
 
+    def testEvalTemplate(self):
+        layer = QgsVectorLayer("Point?field=a:int&field=b:string", "test eval-template", "memory")
+        context = layer.createExpressionContext()
+
+        expression = QgsExpression("eval_template('123 [% \"b\" %] 789')")
+        expression.prepare(context)
+        columns = expression.referencedColumns()
+
+        # Insure prepare has returned all attributes as referenced columns with feature-less context
+        self.assertTrue(QgsFeatureRequest.ALL_ATTRIBUTES in columns)
+
+        feature = QgsFeature(layer.fields())
+        feature.setAttributes([1, '456'])
+        context.setFeature(feature)
+
+        self.assertEqual(expression.evaluate(context), '123 456 789')
+
     def testExceptionDuringEvalReturnsTraceback(self):
         QgsExpression.registerFunction(self.raise_exception)
         exp = QgsExpression('raise_exception()')