More content assist problems

[cdietrich]

we have a grammar like

grammar HelloWorld

entry MyRoot: 
    'package' package=QualifiedName
    objects+=MyObject*
    thing=Thing;

MyObject:
    'object' name=ID 
;

Thing:
    'thing' name=ID '{' shape=ThingBody '}';

ThingBody:
    'shape' 'based-on' baseNode=NodeType '{' content+=(ThingField)* '}';

fragment PropertyHeaderFragment:
    (optional?='optional')? 'property';


fragment PropertyTypeFragment:
    ':' type=Type;

Type:
    value=('Text'|'Number');

ThingField:
    PropertyHeaderFragment 
    (({infer ThingOwnProperty} name=ID  PropertyTypeFragment) | 
    ({infer ThingMappedProperty} property=[MyObject:ID]));

NodeType:
    'node' '<' name=ID '>';

QualifiedName returns string:
    ID ('.' ID)*;

hidden terminal WS: /\s+/;
terminal ID: /[_a-zA-Z][\w_]*/;

hidden terminal ML_COMMENT: /\/\*[\s\S]*?\*\//;
hidden terminal SL_COMMENT: /\/\/[^\n\r]*/;

with this model

package mysample

object exampleField
thing Example {
	shape based-on node<ExampleNode> {

		optional property nodeField1: Text

		property exampleField
        property exampleField2 : Text
		property exampleField3 : |
	}
}

content assist does not work. any idea how to workaround this problem?

[msujew]

Hey @cdietrich,

it seems like the parser (both normal, and completion parser) have trouble with the grammar due to the common prefix in the alternatives in this part of the code:

ThingField:
    PropertyHeaderFragment 
    (({infer ThingOwnProperty} name=ID  PropertyTypeFragment) | 
    ({infer ThingMappedProperty} property=[MyObject:ID]));

If you enforce that you must use a delimiter like in the following, everything seems to work as expected:

ThingField:
    PropertyHeaderFragment 
    (({infer ThingOwnProperty} name=ID  PropertyTypeFragment ';') | 
    ({infer ThingMappedProperty} property=[MyObject:ID] ';'));

The ID ':' part on its own does not seem to be parsed as a ThingOwnProperty but instead as a ThingMappedProperty with an invalid :. This makes the completion parser think that we're at a diffferent position in the grammar and therefore results in no useful proposals.

[cdietrich]

we are currently looking into the following as workaround:

fragment PropertyTypeFragment:
':' type=Type?;

+ validation
+ filter on follow up keywords if type is undefined.

[msujew]

I see. Yeah that also seems to work pretty well 👍