How to use CommentProvider if language was create using createServicesForGrammar?

[Yokozuna59]

Hi there,

I'm currently trying to create a sample grammar for a test case that has JSDoc using createServicesForGrammar:

it('should handle grammar with one greedy rule', async () => {
  const grammar = `
      grammar Test
      /** Rule */
      entry Rule: 'rule' num=INT;
      /** INT */
      terminal INT: /\\d+/;
    `;
    const services = await createServicesForGrammar({ grammar });
    services.Grammar.rules.forEach((rule) => {
      expect(services.documentation.CommentProvider.getComment(rule)).toBeDefined();
    });
});

The above code fails because the CommentProvider#getComment always returns undefined.

Is this expected? It's working fine if I created the language using createDefaultCoreModule and similar functions.

[msujew]

Hey @Yokozuna59,

you're asking the language specific service for comments on the grammar language. You need to ask the grammar service explicitly if you want to get comments for grammars. Similarly, the language specific comment provider only works for the language in question, i.e. the Test language.

Note that the Test language has no comment terminal rules, therefore the comment provider will never actually return any comments.

[Yokozuna59]

@msujew Could you provide me with a sample code or just show the functions that should solve the issue? I tried several ways to do so, but none of them were correct.

[msujew]

You would use the createLangiumGrammarServices() method to get the grammar services and with that the grammar comment provider:

import { createLangiumGrammarServices } from 'langium/grammar';
const grammarServices = createLangiumGrammarServices(EmptyFileSystem);
it('should handle grammar with one greedy rule', async () => {
  const grammar = `
      grammar Test
      /** Rule */
      entry Rule: 'rule' num=INT;
      /** INT */
      terminal INT: /\\d+/;
    `;
    const services = await createServicesForGrammar({ grammar });
    services.Grammar.rules.forEach((rule) => {
      expect(grammarServices.documentation.CommentProvider.getComment(rule)).toBeDefined();
    });
});