Can't generate DBML with a database having many-to-many relation

[loicknuchel]

When I try to generate DBML for a database with a many-to-many relation, it fails with:

Cannot read properties of undefined (reading 'fieldIds')

Here is a reproduction code:

const content = `Table users {
  id int [pk]
}

Table projects {
  id int [pk]
}

Ref: projects.id <> users.id // many-to-many
`
const db: Database = (new Parser(undefined)).parse(content, 'dbmlv2')
const res = ModelExporter.export(db, 'dbml', false)

The error is on the last line.
I also tried with a few variations:

• use 'dbml' format instead of 'dbmlv2'
• replace the last line with ModelExporter.export(db.normalize(), 'dbml', true)
• inline relation (id int [pk, ref: <> users.id])

They all fail the same.
If I remove the many-to-many relation, it works well.

Am I doing something bad?

[NQPhuc]

Hello, @loicknuchel.

Thank you for pointing this out. You are not doing it wrong.

Currently, we haven't handled the part of exporting to dbml for model_structure with n-n relationships (only when exporting to SQLs did we turn them into two one-to-many relationships). The reason for this is that n-n concepts are only presented in dbml, so there is no use case for converting n-n relationships from dbml to dbml.

I hope this explanation helps.

[loicknuchel]

Thanks for the explanation.

Indeed the n-n relationships are not native to SQL databases but seems native to other databases, didn't know either ^^

I feel it's a bit strange to have a parser and a generator but they don't match on feature set: it's possible to write n-n relations in DBML but not to generate them ^^

Is it something you may change in the future or do you think it should stay like this?