[expressions] Silently alias "geom" named across to "geometry"

So that was can standardize on using "geometry" as the named argument
insted of mixing "geom" and "geometry" in the public docs.

src/core/expression/qgsexpressionnode.h

@@ -170,6 +170,11 @@ class CORE_EXPORT QgsExpressionNode SIP_ABSTRACT
 
         bool mHasNamedNodes = false;
 
+        /**
+         * Cleans up and standardises the name of a named node.
+         */
+        static QString cleanNamedNodeName( const QString &name );
+
       public:
     };
 

src/core/expression/qgsexpressionnodeimpl.cpp

@@ -52,7 +52,7 @@ QgsExpressionNode::NodeList::~NodeList()
 void QgsExpressionNode::NodeList::append( QgsExpressionNode::NamedNode *node )
 {
   mList.append( node->node );
-  mNameList.append( node->name.toLower() );
+  mNameList.append( cleanNamedNodeName( node->name ) );
   mHasNamedNodes = true;
   delete node;
 }
@@ -82,6 +82,17 @@ QString QgsExpressionNode::NodeList::dump() const
   return msg;
 }
 
+QString QgsExpressionNode::NodeList::cleanNamedNodeName( const QString &name )
+{
+  QString cleaned = name.toLower();
+
+  // upgrade older argument names to standard versions
+  if ( cleaned == QLatin1String( "geom" ) )
+    cleaned = QStringLiteral( "geometry" );
+
+  return cleaned;
+}
+
 
 //
 

tests/src/core/testqgsexpression.cpp

@@ -1038,6 +1038,8 @@ class TestQgsExpression: public QObject
       QTest::newRow( "exterior_ring polygon" ) << "geom_to_wkt(exterior_ring(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1),( 0.1 0.1, 0.1 0.2, 0.2 0.2, 0.2, 0.1, 0.1 0.1))')))" << false << QVariant( "LineString (-1 -1, 4 0, 4 2, 0 2, -1 -1)" );
       QTest::newRow( "exterior_ring line" ) << "exterior_ring(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)'))" << false << QVariant();
       QTest::newRow( "centroid polygon" ) << "geom_to_wkt(centroid( geomFromWKT('POLYGON((0 0,0 9,9 0,0 0))')))" << false << QVariant( "Point (3 3)" );
+      QTest::newRow( "centroid named argument geom" ) << "geom_to_wkt(centroid( geom:=geomFromWKT('POLYGON((0 0,0 9,9 0,0 0))')))" << false << QVariant( "Point (3 3)" );
+      QTest::newRow( "centroid named argument geometry" ) << "geom_to_wkt(centroid( geometry:=geomFromWKT('POLYGON((0 0,0 9,9 0,0 0))')))" << false << QVariant( "Point (3 3)" );
       QTest::newRow( "centroid multi polygon" ) << "geom_to_wkt(centroid( geomFromWKT('MULTIPOLYGON(((0 0,0 1,1 1,1 0,0 0)),((2 0,2 1,3 1,3 0,2 0)))') ))" << false << QVariant( "Point (1.5 0.5)" );
       QTest::newRow( "centroid point" ) << "geom_to_wkt(centroid( geomFromWKT('POINT (1.5 0.5)') ))" << false << QVariant( "Point (1.5 0.5)" );
       QTest::newRow( "centroid line" ) << "geom_to_wkt(centroid( geomFromWKT('LINESTRING (-1 2, 9 12)') ))" << false << QVariant( "Point (4 7)" );