Property value validation as expression vs. literal should be guarded by "${..}" not merely by a single '$' character

[scottkurz]

In OpenLiberty/liberty-tools-eclipse#501, with LSP4MP v0.10.0, we see a validation error with a microprofile-config.properties property:

mp.messaging.outgoing.systemLoad.value.serializer=io.openliberty.guides.models.SystemLoad$SystemLoadSerializer

Looking at the code:

lsp4mp/microprofile.ls/org.eclipse.lsp4mp.ls/src/main/java/org/eclipse/lsp4mp/model/parser/PropertiesParser.java

Lines 173 to 189 in 302b7a1

	private boolean isStopReading(StopReading stop) {
	if (isEndOfText() || isNewLine()) {
	return true;
	}
	switch (stop) {
	case PropertyName:
	return isColonSeparator() || isWhiteSpace();
	case PropertyValue:
	return false;
	case PropertyValueExpression:
	return last == '}';
	case PropertyValueLiteral:
	return current == '$';
	default:
	return isWhiteSpace();
	}
	}

it seems our parser "state machine" switches over to assuming a property expression substitution upon seeing a single '$' character, looking for something like:

prop2=${prop1}

It seems we might need to rework it to look for "${" before assuming a property expression substitution.

That is more complicated parsing, but will stop there having identified the problem.