Bug 149251 Inconsistent Handling of a Non-inheritable ROM Property
For a ROM property defined to be non-inheritable, an empty string property value should be consistently handled as an empty string, not as null. For example, an oda.dataSource extension defines a data source property with canInherit=false. When a oda-data-source handle get saved in a report design, it correctly includes the tag for such property, even when an empty string value is specified. <oda-data-source extensionID="my.oda.plugin" name="my Data Source" id="24"> ... <property name="ApplicationServer"></property> </oda-data-source> However, later when using the DE API to read its property value, a null is returned. Then when the report design is subsequently saved, the property tag is lost. Expects that an empty string value of a non-inhertiable property should be preserved.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
{
			throw new SemanticError( element,
					SemanticError.DESIGN_EXCEPTION_INVALID_ELEMENT_REF );
		}
		return result;
	}
	/**
	 * The property is a simple value list. If property is a list property, the
	 * method will check to see if the current element has the local list value,
	 * if it has, the method returns, otherwise, a copy of the list value
	 * inherited from container or parent will be set locally on the element
	 * itself.
	 * <p>
	 * This method is supposed to be used when we need to change the value of a
	 * composite property( a simple list property ). These kind of property is
	 * inherited as a whole, so when the value changed from a child element.
	 * This method will be called to ensure that a local copy will be made, so
	 * change to the child won't affect the original value in the parent.
	 * 
	 * @param ref
	 *            a reference to a list property or member.
	 */
	void makeLocalCompositeValue( ElementPropertyDefn prop )
	{
		assert prop != null;
		
		ArrayList list = (ArrayList) element.getLocalProperty( module, prop );
		if ( list != null )
			return;