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Whitespace issue with nested blocks [message #1849836]

Fri, 04 February 2022 01:53

Eclipse User

Hello,
I am trying to build a rather small grammar that allows nested segments. First I tried to do it with BEGIN...AND to make it whitespace-aware, but failed to get it working in the first attempt. Hence, I switched back to brackets.

This works fine except that the closing bracket of a nested block does not allow whitespace / indentation.

Here is the relevant part of the grammar:

Segment:
    'segment' subject=Subject
    '{'
    body=SegmentBody
    NL+
    WS* '}'
;

SegmentBody: {SegmentBody}
    (rules+=Rule (NL+ rules+=Rule)*)+
    (segments+=Segment (segments+=Segment)*)?
;

This works fine:

segment Element {
    Abc is Def
    segment ChildElement {
        Abc is Def
}
}

But this does not:

segment Element {
    Abc is Def
    segment ChildElement {
        Abc is Def
    }      <-- no viable input at '}'
}

Can't understand why it does not allow the space chars since I explicitly allowed them using

WS* '}'

What am I missing?

Thanks for your assistance.

[Updated on: Fri, 04 February 2022 01:54] by Moderator

Re: Whitespace issue with nested blocks [message #1849960 is a reply to message #1849836]

Wed, 09 February 2022 15:46

Eclipse User

What do your terminals look like? Is your WS terminal hidden (ie stripped out and ignored)? Maybe there's a sneaky residual WS token handling from your previous synthetic BEGIN white space experiments?

Re: Whitespace issue with nested blocks [message #1849961 is a reply to message #1849960]

Wed, 09 February 2022 16:13

Eclipse User

No "hidden" statement in my grammar, but I have this defined:

with org.eclipse.xtext.common.Terminals

which includes

hidden(WS, ML_COMMENT, SL_COMMENT)

In my grammar there are only these lines:

terminal NL: ('\r'? '\n');
//override terminal WS: (' '|'\t'|'\r'|'\n')+;

Do I need to add

hidden(WS)

explicitly to my parser rules?

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