Allow geometries to be set separate to features in expression contexts

Refs #46455 -- we need a way to separate these too, as we don't always
want $geometry to refer to a feature's geometry

python/core/auto_generated/qgsexpressioncontext.sip.in

@@ -333,6 +333,49 @@ Removes any feature associated with the scope.
 .. seealso:: :py:func:`hasFeature`
 
 .. versionadded:: 3.0
+%End
+
+    bool hasGeometry() const;
+%Docstring
+Returns ``True`` if the scope has a geometry associated with it.
+
+.. seealso:: :py:func:`geometry`
+
+.. versionadded:: 3.24
+%End
+
+    QgsGeometry geometry() const;
+%Docstring
+Sets the geometry associated with the scope.
+
+.. seealso:: :py:func:`setGeometry`
+
+.. seealso:: :py:func:`hasGeometry`
+
+.. versionadded:: 3.24
+%End
+
+    void setGeometry( const QgsGeometry &geometry );
+%Docstring
+Convenience function for setting a ``geometry`` for the scope. Any existing
+geometry set by the scope will be overwritten.
+
+.. seealso:: :py:func:`removeGeometry`
+
+.. seealso:: :py:func:`geometry`
+
+.. versionadded:: 3.24
+%End
+
+    void removeGeometry();
+%Docstring
+Removes any geometry associated with the scope.
+
+.. seealso:: :py:func:`setGeometry`
+
+.. seealso:: :py:func:`hasGeometry`
+
+.. versionadded:: 3.24
 %End
 
     void setFields( const QgsFields &fields );
@@ -692,6 +735,35 @@ Returns ``True`` if the context has a feature associated with it.
 Convenience function for retrieving the feature for the context, if set.
 
 .. seealso:: :py:func:`setFeature`
+%End
+
+    void setGeometry( const QgsGeometry &geometry );
+%Docstring
+Convenience function for setting a ``geometry`` for the context. The geometry
+will be set within the last scope of the context, so will override any
+existing geometries within the context.
+
+.. seealso:: :py:func:`geometry`
+
+.. versionadded:: 3.24
+%End
+
+    bool hasGeometry() const;
+%Docstring
+Returns ``True`` if the context has a geometry associated with it.
+
+.. seealso:: :py:func:`geometry`
+
+.. versionadded:: 3.24
+%End
+
+    QgsGeometry geometry() const;
+%Docstring
+Convenience function for retrieving the geometry for the context, if set.
+
+.. seealso:: :py:func:`setGeometry`
+
+.. versionadded:: 3.24
 %End
 
     void setFields( const QgsFields &fields );

src/core/qgsexpressioncontext.cpp

@@ -45,6 +45,8 @@ QgsExpressionContextScope::QgsExpressionContextScope( const QgsExpressionContext
   , mVariables( other.mVariables )
   , mHasFeature( other.mHasFeature )
   , mFeature( other.mFeature )
+  , mHasGeometry( other.mHasGeometry )
+  , mGeometry( other.mGeometry )
 {
   QHash<QString, QgsScopedExpressionFunction * >::const_iterator it = other.mFunctions.constBegin();
   for ( ; it != other.mFunctions.constEnd(); ++it )
@@ -59,6 +61,8 @@ QgsExpressionContextScope &QgsExpressionContextScope::operator=( const QgsExpres
   mVariables = other.mVariables;
   mHasFeature = other.mHasFeature;
   mFeature = other.mFeature;
+  mHasGeometry = other.mHasGeometry;
+  mGeometry = other.mGeometry;
 
   qDeleteAll( mFunctions );
   mFunctions.clear();
@@ -529,8 +533,7 @@ void QgsExpressionContext::setFeature( const QgsFeature &feature )
 
 bool QgsExpressionContext::hasFeature() const
 {
-  const auto constMStack = mStack;
-  for ( const QgsExpressionContextScope *scope : constMStack )
+  for ( const QgsExpressionContextScope *scope : mStack )
   {
     if ( scope->hasFeature() )
       return true;
@@ -551,6 +554,37 @@ QgsFeature QgsExpressionContext::feature() const
   return QgsFeature();
 }
 
+void QgsExpressionContext::setGeometry( const QgsGeometry &geometry )
+{
+  if ( mStack.isEmpty() )
+    mStack.append( new QgsExpressionContextScope() );
+
+  mStack.last()->setGeometry( geometry );
+}
+
+bool QgsExpressionContext::hasGeometry() const
+{
+  for ( const QgsExpressionContextScope *scope : mStack )
+  {
+    if ( scope->hasGeometry() )
+      return true;
+  }
+  return false;
+}
+
+QgsGeometry QgsExpressionContext::geometry() const
+{
+  //iterate through stack backwards, so that higher priority variables take precedence
+  QList< QgsExpressionContextScope * >::const_iterator it = mStack.constEnd();
+  while ( it != mStack.constBegin() )
+  {
+    --it;
+    if ( ( *it )->hasGeometry() )
+      return ( *it )->geometry();
+  }
+  return QgsGeometry();
+}
+
 void QgsExpressionContext::setFields( const QgsFields &fields )
 {
   if ( mStack.isEmpty() )

src/core/qgsexpressioncontext.h

@@ -326,6 +326,39 @@ class CORE_EXPORT QgsExpressionContextScope
      */
     void removeFeature() { mHasFeature = false; mFeature = QgsFeature(); }
 
+    /**
+     * Returns TRUE if the scope has a geometry associated with it.
+     * \see geometry()
+     * \since QGIS 3.24
+     */
+    bool hasGeometry() const { return mHasGeometry; }
+
+    /**
+     * Sets the geometry associated with the scope.
+     * \see setGeometry()
+     * \see hasGeometry()
+     * \since QGIS 3.24
+     */
+    QgsGeometry geometry() const { return mGeometry; }
+
+    /**
+     * Convenience function for setting a \a geometry for the scope. Any existing
+     * geometry set by the scope will be overwritten.
+
+     * \see removeGeometry()
+     * \see geometry()
+     * \since QGIS 3.24
+     */
+    void setGeometry( const QgsGeometry &geometry ) { mHasGeometry = true; mGeometry = geometry; }
+
+    /**
+     * Removes any geometry associated with the scope.
+     * \see setGeometry()
+     * \see hasGeometry()
+     * \since QGIS 3.24
+     */
+    void removeGeometry() { mHasGeometry = false; mGeometry = QgsGeometry(); }
+
     /**
      * Convenience function for setting a fields for the scope. Any existing
      * fields set by the scope will be overwritten.
@@ -353,6 +386,8 @@ class CORE_EXPORT QgsExpressionContextScope
     QHash<QString, QgsScopedExpressionFunction * > mFunctions;
     bool mHasFeature = false;
     QgsFeature mFeature;
+    bool mHasGeometry = false;
+    QgsGeometry mGeometry;
 };
 
 /**
@@ -650,6 +685,30 @@ class CORE_EXPORT QgsExpressionContext
      */
     QgsFeature feature() const;
 
+    /**
+     * Convenience function for setting a \a geometry for the context. The geometry
+     * will be set within the last scope of the context, so will override any
+     * existing geometries within the context.
+
+     * \see geometry()
+     * \since QGIS 3.24
+     */
+    void setGeometry( const QgsGeometry &geometry );
+
+    /**
+     * Returns TRUE if the context has a geometry associated with it.
+     * \see geometry()
+     * \since QGIS 3.24
+     */
+    bool hasGeometry() const;
+
+    /**
+     * Convenience function for retrieving the geometry for the context, if set.
+     * \see setGeometry()
+     * \since QGIS 3.24
+     */
+    QgsGeometry geometry() const;
+
     /**
      * Convenience function for setting a fields for the context. The fields
      * will be set within the last scope of the context, so will override any

tests/src/core/testqgsexpressioncontext.cpp

@@ -44,6 +44,7 @@ class TestQgsExpressionContext : public QObject
     void contextStackFunctions();
     void evaluate();
     void setFeature();
+    void setGeometry();
     void setFields();
     void takeScopes();
     void highlighted();
@@ -486,6 +487,35 @@ void TestQgsExpressionContext::setFeature()
   QCOMPARE( contextWithScope.feature().id(), 50LL );
 }
 
+void TestQgsExpressionContext::setGeometry()
+{
+  QgsGeometry g( QgsGeometry::fromPointXY( QgsPointXY( 1, 2 ) ) );
+  QgsExpressionContextScope scope;
+  scope.setGeometry( g );
+  QVERIFY( scope.hasGeometry() );
+  QCOMPARE( scope.geometry().asWkt(), QStringLiteral( "Point (1 2)" ) );
+  scope.removeGeometry();
+  QVERIFY( !scope.hasGeometry() );
+  QVERIFY( scope.geometry().isNull() );
+
+  //test setting a geometry in a context with no scopes
+  QgsExpressionContext emptyContext;
+  QVERIFY( !emptyContext.hasGeometry() );
+  QVERIFY( emptyContext.geometry().isNull() );
+  emptyContext.setGeometry( g );
+  //setGeometry should have created a scope
+  QCOMPARE( emptyContext.scopeCount(), 1 );
+  QVERIFY( emptyContext.hasGeometry() );
+  QCOMPARE( emptyContext.geometry().asWkt(), QStringLiteral( "Point (1 2)" ) );
+
+  QgsExpressionContext contextWithScope;
+  contextWithScope << new QgsExpressionContextScope();
+  contextWithScope.setGeometry( g );
+  QCOMPARE( contextWithScope.scopeCount(), 1 );
+  QVERIFY( contextWithScope.hasGeometry() );
+  QCOMPARE( contextWithScope.geometry().asWkt(), QStringLiteral( "Point (1 2)" ) );
+}
+
 void TestQgsExpressionContext::setFields()
 {
   QgsFields fields;