UNION expression select column type can still be interpereted null despite IS NOT NULL WHERE statement

[codygordon]

Take this expression builder example:

eb(
  'folderId',
  'in',
  eb
    .selectFrom('folder')
    .select(['id'])          
    .union(
      eb
        .selectFrom('contentPermission')
        .select(['folderId as id'])
        .where('contentPermission.folderId', 'is not', null)
    ),
)

The contentPermission table definition has folderId as a nullable column, so TS is throwing an error as the folderId type does not exactly match the "parent" query id column type (not nullable), however we know the union result would never result in any null values due to the where statement.

.

In lieu of a fix, is there a recommended workaround for this situation?

[koskimas]

This has been answered many times. It's impossible to fix this for anything other than trivial cases, and even that fix would complicate the types a lot and basically make the library unusable. The query builder type would be changed by where calls, making reassignment to the same variable often impossible. All that just to fix trivial one condition expressions. As soon as there's a more complex where statement, it wouldn't be possible anymore.

[koskimas]

I just added an example for dealing with these cases

https://kysely.dev/docs/examples/SELECT/not-null

[codygordon]

Thank you, appreciate the response!