External validation alternative

[renanBritz]

Support plan

• is this issue currently blocking your project? (yes/no): no
• is this issue affecting a production system? (yes/no): no

Context

• node version: 12.7.0
• module version: ^17.1.1
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): nestjs
• any other relevant information:

How can we help?

Hello!

For async validation (e.g check if username is unique in database) you have recommended multiple times to use external() validator, but it's not a good solution! Simply because it offers no context to which field presented the error, and it runs AFTER the rest of the schema has been validated. Or am I missing something in the documentation?

I don't know if this is a design limitation, but it's simply not helpful to developers.

I don't mean to be disrespectful, but such a large library that handles a very important aspect of a server-side app needs to add more consideration to this common use case.

Regards!

[hueniverse]

I plan to improve the external user experience in the future. That said, while this is a somewhat common use case, it is still less common than using joi for sync validations and unfortunately in JS you can have both in the same code. This would require duplicating the entire library.

[jonyeezs]

PR #2773 may solve this