Add method to remove feature from a QgsExpressionContextScope

python/core/qgsexpressioncontext.sip

@@ -197,10 +197,8 @@ class QgsExpressionContextScope
 
     void setFeature( const QgsFeature& feature );
 
-    /** Convenience function for setting a fields for the scope. Any existing
-     * fields set by the scope will be overwritten.
-     * @param fields fields for scope
-     */
+    void removeFeature();
+
     void setFields( const QgsFields& fields );
 };
 

src/core/qgsexpressioncontext.h

@@ -269,9 +269,19 @@ class CORE_EXPORT QgsExpressionContextScope
     /** Convenience function for setting a feature for the scope. Any existing
      * feature set by the scope will be overwritten.
      * @param feature feature for scope
+     * @see removeFeature()
+     * @see feature()
      */
     void setFeature( const QgsFeature& feature ) { mHasFeature = true; mFeature = feature; }
 
+    /**
+     * Removes any feature associated with the scope.
+     * @note added in QGIS 3.0
+     * @see setFeature()
+     * @see hasFeature()
+     */
+    void removeFeature() { mHasFeature = false; mFeature = QgsFeature(); }
+
     /** Convenience function for setting a fields for the scope. Any existing
      * fields set by the scope will be overwritten.
      * @param fields fields for scope

tests/src/core/testqgsexpressioncontext.cpp

@@ -437,6 +437,9 @@ void TestQgsExpressionContext::setFeature()
   scope.setFeature( feature );
   QVERIFY( scope.hasFeature() );
   QCOMPARE( scope.feature().id(), 50LL );
+  scope.removeFeature();
+  QVERIFY( !scope.hasFeature() );
+  QVERIFY( !scope.feature().isValid() );
 
   //test setting a feature in a context with no scopes
   QgsExpressionContext emptyContext;