Help developers better handle SQL errors

Problem

We sometimes want to handle SQL errors differently to return a proper error to the frontend. For example, we might want to display email already used if a unique violation is detected on the field. The current situation is that we have to check against an obscure error code (P2002 for example for unique validation failure) and then go into meta.target to get which field broke. Its never easy to extract meaningful stuff from ORM(-like) tools despite being a very common operation and I think it could be a factor of differentiation for prisma.

Propositions

I see two possible way of dealing more gracefully with that:

1. Create more custom error types in javascript and use instanceof to catch them. This would look like:

     try {
       const user = await prisma.user.create({ data });
       return res.status(204).send();
     } catch (err) {
       if (err instanceof PrismaUniqueViolationError) {
         return res.status(400).send('DUPLICATE EMAIL');
       }
       return res.status(400).send('BAD REQUEST');
     }
   

2. Create an enum of errors. This would look like

     try {
       const user = await prisma.user.create({ data });
       return res.status(204).send();
     } catch (err) {
       if (err.code === PrismaErrors.UniqueViolation) {
         return res.status(400).send('DUPLICATE EMAIL');
       }
       return res.status(400).send('BAD REQUEST');
     }
   

I also think there should be helpers to extract the problematic fields from the error. Something like:

if (err.code === PrismaErrors.UniqueViolation) {
    const duplicateFields = extractErrorFields(err);
    return res.status(400).json({ code: 'unique_violation', fields: duplicateFields});
}

[steebchen]

If possible, I’d like to have something like this which I’ve initially proposed in prisma/prisma-client-js#720:

try {
  await db.users.insert(newUser)
} catch (err) {
  if (err instanceof UniqueConstraintViolation) {
    // not sure if typescript can infer the error, but I think it can
    if (err.field == "email") {
      console.log("user already exists with this email")
      return
    }
    console.log("unique constraint violation on another field: " + err.field)
  }
}

[ayush-goyal]

Any updates on the status of this?