Syntax highlighting for meta model elements in property definitions

[jjhugues]

Some elements in property definitions are not correctly highlighted. Most of them are meta model reserved words.
See for instance EMV2.aadl,

OccurrenceDistribution : EMV2::DistributionSpecification
applies to ({emv2}**error propagation, {emv2}**error flow, {emv2}**error behavior event
,{emv2}**error behavior state,{emv2}**error type,{emv2}**type set);

or Communication_Properties, properties that applies to connection

[AaronGreenhouse]

Looking at the above property definitions it is the case the some keywords are not properly formatted as keywords:

• connection
• specfication
• error
• propagation
• behavior
• state

[AaronGreenhouse]

These has to do with the weird way that the applies to clause is implemented in the parser. In particular, connection and specification are not actually keywords in the AADL grammar Aadl2.xtext. Furthermore more, in the EMV2 case, the only keywords that are highlighted are those that are also keywords in AADL core grammar. Anything that is a keyword in the EMV2 grammar only is not highlighted.

connection and specification could be added to the CoreKeyWord rule, but I don't know what else that might affect.

The EMV2 keywords cannot and should not be added to the main AADL grammar. Some way of the combining the two grammars would have to exist (and may exist in the general mechanism that handes AADL language extensions).

Probably the correct thing to do here is to make sure that NONE of the items in the applies to list are highlighted. But I don't know how to do that either.

[AaronGreenhouse]

With regard to suppressing styling of the keywords, I found this. Seems to cover what I want to do. Haven't tried to understand it yet.

https://stackoverflow.com/questions/42603874/disable-highlighting-of-keywords-when-used-in-identifiers

[AaronGreenhouse]

Okay, the above link is helpful, but not the full story:

Problem 1

The Aadl2SemanticHighlightingCalculator overrides provideHighlightingFor, which in the DefaultSemanticHighlightingCalculator controls the traversal of the syntax tree that calls highlightElement. I had to introduce a call to super.provideHighlightingFor before the search for annex clauses.

Problem 2

This one caused me bigger problems. I overrode highlightElement() based on the linked example so that it looked like

	protected boolean highlightElement(EObject object,
			org.eclipse.xtext.ide.editor.syntaxcoloring.IHighlightedPositionAcceptor acceptor,
			CancelIndicator cancelIndicator) {
		if (object instanceof MetaclassReference) {
			highlightFeature(acceptor, object, Aadl2Package.eINSTANCE.getMetaclassReference_MetaclassName(),
					HighlightingStyles.DEFAULT_ID);
			return true;
		}
		return super.highlightElement(object, acceptor, cancelIndicator);
	}

But the results seemed haphazard. In particular, sometimes the keyword port when used in the "applies to" clause was styled as DEFAULT and sometimes it was styled as KEYWORD. Ultimately the problem was revealed to be the method DefaultSemanticHighlightingCalculator.highlightFeature(), which for some reason only applies to style to the first child of the given node! So I had to be more explicit in my hightlightElement:

	protected boolean highlightElement(EObject object,
			org.eclipse.xtext.ide.editor.syntaxcoloring.IHighlightedPositionAcceptor acceptor,
			CancelIndicator cancelIndicator) {
		if (object instanceof MetaclassReference) {
			/*
			 * XXX: Want to call highlightFeature() directly, but for some reason it only affects the first child of the given node! This doesn't work if we
			 * have something like "event port", because then the style isn't applied to "port". Crazy.
			 */
//			highlightFeature(acceptor, object, Aadl2Package.eINSTANCE.getMetaclassReference_MetaclassName(),
//					HighlightingStyles.DEFAULT_ID);
			final List<INode> children = NodeModelUtils.findNodesForFeature(object,
					Aadl2Package.eINSTANCE.getMetaclassReference_MetaclassName());
			for (final INode child : children) {
				highlightNode(acceptor, child, HighlightingStyles.DEFAULT_ID);
			}
			return true;
		}
		return super.highlightElement(object, acceptor, cancelIndicator);
	}

[AaronGreenhouse]

So to be clear: I have altered the syntax highlighting so that Meta Class References are styled as default text. This overrides any styling that keywords used as part of the meta class class reference might otherwise have.

[AaronGreenhouse]

Also, I replaced the use of the deprecated org.eclipse.xtext.ui.editor.syntaxcoloring.ISemanticHighlightingCalculator with the newer org.eclipse.xtext.ide.editor.syntaxcoloring.ISemanticHighlightingCalculator.