Allow setting scalar list default values

[casey-chow]

Problem

I'm currently migrating a schema which has a non-empty string default. My schema looks like this:

model Person {
  emails String[]
}

This is how it is generated from prisma introspect, decided from #1110. However, when running prisma migrate dev, the generated migration then attempts to remove the default, generating:

ALTER TABLE "Person" ALTER COLUMN "emails" DROP DEFAULT;

Removing this and attempting to add a default using dbgenerated leads to the following error:

Error parsing attribute "@default": Cannot set a default value on list field.

Suggested solution

As far as I can tell, this error is entirely artificial at this point because the release of 2.16.0 introduced a workable syntax for scalar lists via dbgenerated. I'd like to propose simply removing this check:

https://github.com/prisma/prisma-engines/blob/215319b1f112e9e5b5a1f2d2b0553982d2669776/libs/datamodel/core/src/transform/ast_to_dml/db/attributes.rs#L320-L322

Alternatives

None considered, as I haven't found any drawbacks to this proposal.

Additional context

[pantharshit00]

Thanks for bringing this up, I agree we should finally decide on how we can support defaults for scalar lists.

[pantharshit00]

Can you also try adding @default(dbgenerated()) which might prevent the faulty migration? (We might be actually blocking this no harm in trying)

model Person {
  emails String[] @default(dbgenerated())
}

[casey-chow]

Can you also try adding @default(dbgenerated()) which might prevent the faulty migration? (We might be actually blocking this no harm in trying)

model Person {
  emails String[] @default(dbgenerated())
}

No dice, same error 😞

[nicklloyd]

This one is a bit painful...

We're running:

version "3.8.1"

Updating migration.sql to include the default doesn't help either are seems like any prisma migrate run also generates a new migration to drop the default...

Any other work arounds?

[nicklloyd]

Last sentence https://www.prisma.io/docs/concepts/components/prisma-client/working-with-fields/working-with-scalar-lists-arrays#null-values-in-arrays states:

To work around this issue, you can set the default value of array fields to {} at a database level

But have been unable to use migrate without it reseting, even if I alter the table in PG itself

[janpio]

Open an issue about migrations not picking that up correct please and provide all the information the issue template asks for @nicklloyd . If that is the case, it is not intended.

[janpio]

Internal note:
There are some more similar issues collected in this column in a project board: https://github.com/orgs/prisma/projects/64#column-17788443