Do not validate `default` for `@db.MediumText` as it is not allowed in MySQL

Problem

If setting a default value on a field with @db.MediumText (mysql) running migrate after a format and generate errors with shadow db error and migration fail and then have to reset database and lose all the data and thinking/suggesting that prisma format should catch this.

model Stuff {
  id                    String @id
// creates unrecoverable migration issue - @db.MediumText @default("") 
  label                 String @db.MediumText @default("")
}

Running prisma generate prisma format all seems fine, then run prisma migrate and explodes and have to accept nuke of the db and start over.

My current solution when i encounter unrecoverable migration errors or tokyo drift like this is to use mysql workbench export wizard to export each table in db, but this won’t be sustainable as # of tables increase / go to prod etc. Maybe there is a way to backup whole db and force a migration or such.

Suggested solution

prisma format should strip @default("") from any keys that are String @db.MediumText

Alternatives

tbd

Additional context

mysql 8.0 and node v14.15.3

“@prisma/client”: “^2.22.1”, “express”: “^4.17.1”, “typescript”: “^4.2.3”

[pantharshit00]

code/reproductions/issue-7080 is 📦 v1.0.0 via  v14.17.0
❯ npx prisma migrate dev
Environment variables loaded from prisma\.env
Prisma schema loaded from prisma\schema.prisma
Datasource "db": MySQL database "issue_7080" at "localhost:3306"

MySQL database issue_7080 created at localhost:3306

√ Enter a name for the new migration: ... init
Error: P3018

A migration failed to apply. New migrations can not be applied before the error is recovered from. Read more about how t
o resolve migration issues in a production database: https://pris.ly/d/migrate-resolve

Migration name: 20210527170531_init

Database error code: 1101

Database error:
BLOB, TEXT, GEOMETRY or JSON column 'label' can't have a default value

I can reproduce this and I think we should disallow this in the schema level validator rather than stripping this in format. Marking this as a confirmed bug.

[do4gr]

While migrate cannot persist the default value on the db level, the client will still be able to write the value to the database in cases where no value is provided in the query. Rejecting this via a validation would break this functionality.