Add methods to remove variables from global/project scope

python/core/qgsexpressioncontext.sip

@@ -726,6 +726,7 @@ class QgsExpressionContextUtils
  \param value variable value
 .. seealso:: setGlobalVariable()
 .. seealso:: globalScope()
+.. seealso:: removeGlobalVariable()
 %End
 
     static void setGlobalVariables( const QVariantMap &variables );
@@ -735,6 +736,16 @@ class QgsExpressionContextUtils
  \param variables new set of global variables
 .. seealso:: setGlobalVariable()
 .. seealso:: globalScope()
+.. seealso:: removeGlobalVariable()
+%End
+
+    static void removeGlobalVariable( const QString &name );
+%Docstring
+ Remove a global context variable.
+ \param name variable name
+.. seealso:: setGlobalVariable()
+.. seealso:: setGlobalVariables()
+.. seealso:: globalScope()
 %End
 
     static QgsExpressionContextScope *projectScope( const QgsProject *project ) /Factory/;
@@ -754,6 +765,7 @@ class QgsExpressionContextUtils
  \param name variable name
  \param value variable value
 .. seealso:: setProjectVariables()
+.. seealso:: removeProjectVariable()
 .. seealso:: projectScope()
 %End
 
@@ -764,6 +776,17 @@ class QgsExpressionContextUtils
  \param project Project to apply changes to
  \param variables new set of project variables
 .. seealso:: setProjectVariable()
+.. seealso:: removeProjectVariable()
+.. seealso:: projectScope()
+%End
+
+    static void removeProjectVariable( QgsProject *project, const QString &name );
+%Docstring
+ Remove project context variable.
+ \param project Project to apply changes to
+ \param name variable name
+.. seealso:: setProjectVariable()
+.. seealso:: setProjectVariables()
 .. seealso:: projectScope()
 %End
 

src/core/qgsexpressioncontext.cpp

@@ -593,6 +593,14 @@ void QgsExpressionContextUtils::setGlobalVariables( const QVariantMap &variables
   QgsApplication::setCustomVariables( variables );
 }
 
+void QgsExpressionContextUtils::removeGlobalVariable( const QString &name )
+{
+  QVariantMap vars = QgsApplication::customVariables();
+  if ( vars.remove( name ) )
+    QgsApplication::setCustomVariables( vars );
+}
+
+
 /// @cond PRIVATE
 
 class GetNamedProjectColor : public QgsScopedExpressionFunction
@@ -796,6 +804,18 @@ void QgsExpressionContextUtils::setProjectVariables( QgsProject *project, const
   project->setCustomVariables( variables );
 }
 
+void QgsExpressionContextUtils::removeProjectVariable( QgsProject *project, const QString &name )
+{
+  if ( !project )
+  {
+    return;
+  }
+
+  QVariantMap vars = project->customVariables();
+  if ( vars.remove( name ) )
+    project->setCustomVariables( vars );
+}
+
 QgsExpressionContextScope *QgsExpressionContextUtils::layerScope( const QgsMapLayer *layer )
 {
   QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Layer" ) );

src/core/qgsexpressioncontext.h

@@ -733,6 +733,7 @@ class CORE_EXPORT QgsExpressionContextUtils
      * \param value variable value
      * \see setGlobalVariable()
      * \see globalScope()
+     * \see removeGlobalVariable()
      */
     static void setGlobalVariable( const QString &name, const QVariant &value );
 
@@ -742,9 +743,19 @@ class CORE_EXPORT QgsExpressionContextUtils
      * \param variables new set of global variables
      * \see setGlobalVariable()
      * \see globalScope()
+     * \see removeGlobalVariable()
      */
     static void setGlobalVariables( const QVariantMap &variables );
 
+    /**
+     * Remove a global context variable.
+     * \param name variable name
+     * \see setGlobalVariable()
+     * \see setGlobalVariables()
+     * \see globalScope()
+     */
+    static void removeGlobalVariable( const QString &name );
+
     /**
      * Creates a new scope which contains variables and functions relating to a QGIS project.
      * For instance, project path and title, and variables specified through the project properties.
@@ -760,6 +771,7 @@ class CORE_EXPORT QgsExpressionContextUtils
      * \param name variable name
      * \param value variable value
      * \see setProjectVariables()
+     * \see removeProjectVariable()
      * \see projectScope()
      */
     static void setProjectVariable( QgsProject *project, const QString &name, const QVariant &value );
@@ -770,10 +782,21 @@ class CORE_EXPORT QgsExpressionContextUtils
      * \param project Project to apply changes to
      * \param variables new set of project variables
      * \see setProjectVariable()
+     * \see removeProjectVariable()
      * \see projectScope()
      */
     static void setProjectVariables( QgsProject *project, const QVariantMap &variables );
 
+    /**
+     * Remove project context variable.
+     * \param project Project to apply changes to
+     * \param name variable name
+     * \see setProjectVariable()
+     * \see setProjectVariables()
+     * \see projectScope()
+     */
+    static void removeProjectVariable( QgsProject *project, const QString &name );
+
     /**
      * Creates a new scope which contains variables and functions relating to a QgsMapLayer.
      * For instance, layer name, id and fields.

tests/src/core/testqgsexpressioncontext.cpp

@@ -554,6 +554,15 @@ void TestQgsExpressionContext::globalScope()
   QCOMPARE( globalScope2->variable( "newvar2" ).toString(), QString( "val2" ) );
 
   delete globalScope2;
+
+  //test removeGlobalVariables
+  QgsExpressionContextUtils::setGlobalVariable( QStringLiteral( "key" ), "value" );
+  QgsExpressionContextScope *globalScope3 = QgsExpressionContextUtils::globalScope();
+  QVERIFY( globalScope3->hasVariable( "key" ) );
+  QgsExpressionContextUtils::removeGlobalVariable( QStringLiteral( "key" ) );
+  globalScope3 = QgsExpressionContextUtils::globalScope();
+  QVERIFY( !globalScope3->hasVariable( "key" ) );
+  delete globalScope3;
 }
 
 void TestQgsExpressionContext::projectScope()
@@ -599,6 +608,15 @@ void TestQgsExpressionContext::projectScope()
   QCOMPARE( projectScope->variable( "newvar1" ).toString(), QString( "val1" ) );
   QCOMPARE( projectScope->variable( "newvar2" ).toString(), QString( "val2" ) );
   delete projectScope;
+
+  //test removeProjectVariable
+  QgsExpressionContextUtils::setProjectVariable( project, QStringLiteral( "key" ), "value" );
+  projectScope = QgsExpressionContextUtils::projectScope( project );
+  QVERIFY( projectScope->hasVariable( "key" ) );
+  QgsExpressionContextUtils::removeProjectVariable( project, QStringLiteral( "key" ) );
+  projectScope = QgsExpressionContextUtils::projectScope( project );
+  QVERIFY( !projectScope->hasVariable( "key" ) );
+  delete projectScope;
   projectScope = 0;
 
   //test project scope functions