defaultRaw current_timestamp(3) not taken into account in generated migration

[kalu06]

Describe the bug
When specifying defaultRaw: 'CURRENT_TIMESTAMP(3)' on a Date property on an entity, the generated migration will contain default current_timestamp(0)

To Reproduce
Steps to reproduce the behavior:

1. Use the mysql type in mikro-orm.config.ts
2. Create an entity that contains a Date property like this:

@Property({
  columnType: 'timestamp(3)',
  defaultRaw: 'CURRENT_TIMESTAMP(3)',
 })
updatedAt!: Date;

4. Generate a migration using npx mikro-orm migration:create

Expected behavior
I would expect the migration to contain default current_timestamp(3) as specified in the entity defaultRaw.

Versions

Dependency	Version
node	18.6.0
typescript	5.2.2
mikro-orm	5.8.3

[B4nan]

Looks like an issue with defaultRaw, as with default it behaves correctly (but you can't use that for SQL functions, so won't help with this).

[kalu06]

Digging in the source code, I think I found the root cause in https://github.com/mikro-orm/mikro-orm/blob/master/packages/knex/src/schema/SchemaHelper.ts#L251.
It seems that knex uses the length prop to replace the precision of the current_timestamp from defaultRaw.

Changing my example above with the following seems to work:

@Property({
  columnType: 'timestamp(3)',
  defaultRaw: 'CURRENT_TIMESTAMP(3)',
  length: 3,
 })
updatedAt!: Date;

[B4nan]

Hmm interesting, I'd say the problem is that we shouldn't touch the user-provided defaultRaw, just like we never touch the columnType option.

[B4nan]

Right, the main issue here is the inference of the length for datetime columns were not implemented, we just used the platform default. That's why providing length explicitly helps.

https://github.com/mikro-orm/mikro-orm/blob/master/packages/knex/src/schema/DatabaseTable.ts#L85

[kalu06]

@B4nan thanks for fixing this so quickly 👍