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How could empty elements be allowed in a whitespace-aware DSL in xtext? [message #1847443]

Wed, 27 October 2021 08:39

Weixing Zhang

Messages: 19
Registered: April 2021

Junior Member

Hey,

I have modified the domainmodel example into a whitespace DSL, see as follows:

datatype String
 
entity Blog
    title: String
    many posts: Post
 
entity HasAuthor
    author: String
 
entity Post extends HasAuthor
    title: String
    content: String
    many comments: Comment
 
entity Comment extends HasAuthor
    content: String

it's quite nice, but the problem now is that I have to type in an element underneath an entity, even though I have make the expression "(features+=Feature)*" optional. See as follows:

datatype String
 
entity Blog
    title: String
    many posts: Post
 
entity HasAuthor
 
entity Post extends HasAuthor
    title: String
    content: String
    many comments: Comment
 
entity Comment extends HasAuthor
    content: String

Then I would receive error message at line "entity Post...", that:
mismatched input 'entity' expecting RULE_BEGIN.

So how could I make it allow empty element exist?

[Updated on: Wed, 27 October 2021 08:40]

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Re: How could empty elements be allowed in a whitespace-aware DSL in xtext? [message #1847446 is a reply to message #1847443]

Wed, 27 October 2021 09:43

Christian Dietrich

Messages: 14349
Registered: July 2009

Senior Member

the naive variant does not work?

Model:
	entities+=Entity*;

Entity: "entity" name=ID
(BEGIN
	f+=Field*
END)?;	

Field:
	name=ID
;

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