template error: attribute parser isn't defined

[akonsu]

Grammar:

grammar Language;

@lexer::members {var blah = true;}

P : T ',' T ;
T : [a-z]+ {blah}? ;
init: P EOF ;

generates an error below when using Javascript target (antlr4 -Dlanguage=JavaScript Language.g4):

warning(22):  template error: context [/LexerFile /Lexer /dumpActions /RuleSempredFunction] 1:4 attribute parser isn't defined 

[Hugheth]

I too have this error when compiling the ANTLR Java8.g4 grammar with

 antlr4 -Dlanguage=JavaScript Java8.g4

Using version 4.5.1

[BurtHarris]

Well, I ran into this same message when I tried to add semantic predicates to my lexer. Digging into it some, I think that the fact the error message is referring to 'attribute parser' may be a clue as to the cause. It should be generating a lexer when this occurs.

I think I found the relevant part of the string template in JavaScript.stg, which says:

/* This generates a private method since the predIndex is generated, making an
 * overriding implementation impossible to maintain.
 */
RuleSempredFunction(r, actions) ::= <<
<if(parser)><parser.name><else><lexer.name><endif>.prototype.<r.name>_sempred = function(localctx, predIndex) {
    switch(predIndex) {
        <actions:{index| case <index>:
    return <actions.(index)>;}; separator="\n">
        default:
            throw "No predicate with index:" + predIndex;
    }
};

>>

I don't know STRINGTEMPLATE very well, but it seems like the <else> part of this construct should be rendered, but that it's not getting there. Could the problem be that parser is considered true(ish), but that parser.name is undefined?

Note: the generated code seem to have the appropriate name none-the-less.

[ericvergnaud]

Hi,
from my tests, antlr generates a warning, not an error, and the generated code is correct.
Can you confirm?

[ericvergnaud]

@parrt can you look at my fix-#958 branch, I've tried to get rid of the warning, but it seems that ST can't find the 'parserName' attribute in the LexerFile object model. Not sure what I'm doing wrong...

[parrt]

I get this error

net.js:623
    throw new TypeError('invalid data');
    ^

TypeError: invalid data
    at Socket.write (net.js:623:11)
    at main (/private/var/folders/93/9kzk2ccm8xj8k70059b28jk80000gp/T/BaseNodeTest-main-1481655380368/Test.js:12:20)
    at Object.<anonymous> (/private/var/folders/93/9kzk2ccm8xj8k70059b28jk80000gp/T/BaseNodeTest-main-1481655380368/Test.js:15:1)
    at Module._compile (module.js:413:34)
    at Object.Module._extensions..js (module.js:422:10)
    at Module.load (module.js:357:32)
    at Function.Module._load (module.js:314:12)
    at Function.Module.runMain (module.js:447:10)
    at startup (node.js:146:18)
    at node.js:404:3

From

lexer grammar T;

options {language=JavaScript;}

T : 'a' {<True()>}? ;

[parrt]

@ericvergnaud unfortunately either lexer or parser will be undefined. I think I faked it for C++ as:

<if (r.factory.g.lexer)><lexer.name><else><parser.name><endif>

I'll make the patch and add a test. Yep, that fixes it. I'll push but we still have that net.js issue