Enhancing the AST

[paulfrench]

Before I can use my AST for code generation I need to perform a number of validation checks and store some additional information against the AST nodes to make it a lot easier to use the model AST in handlebarjs templates.

Is there a recommended approach for this?

Cheers

[msujew]

Hi,

generally, you should use the ValidationRegistry for validation checks. See how we use it for langium's own grammar language:

https://github.com/langium/langium/blob/main/packages/langium/src/grammar/langium-grammar-validator.ts

For post processing, @spoenemann previously mentioned a method to do this directly after parsing here. If you need validations to run before that, you can override the validateDocument method of the DocumentValidator in a way like this:

async validateDocument(document: LangiumDocument, cancelToken = CancellationToken.None): Promise<Diagnostic[]> {
    const diagnostics = await super.validateDocument(document, cancelToken);
    this.performPostProcessing(document);
    return diagnostics;
}