Alternative idea:

type causer interface {
  Cause() error
}

func ErrCode(err error) ErrorCode { 
  if ce, ok := err.(causer); ok {
    return ErrCode(ce.Cause())
  }

  // ... current ErrCode code
}

This would support github.com/pkg/errors without creating a dependency.

Just two data points:

• https://github.com/pkg/errors is currently imported by 12131 packages
• https://github.com/go-errors/errors is currently imported by 387 packages

Your second alternative is not so bad, but I wonder if this belongs in the sqlite package. I think a user can write their own ErrCode wrapper function and use that instead of sqlite.ErrCode, which can do any kind of handling they want. Is that not the case?

Your second alternative is not so bad, but I wonder if this belongs in the sqlite package. I think a user can write their own ErrCode wrapper function and use that instead of sqlite.ErrCode, which can do any kind of handling they want. Is that not the case?

Well, ErrCode() is used in sqliteutil to determine whether to RELEASE or ROLLBACK at the end of a savepoint so.. yes and no.

(The err that Save()'s releaseFn analyzes would definitely be wrapped)

I suppose I could reimplement Save myself, but as we've seen today, it is tricky to get right :)

sqliteutil.Save is a good argument. If you want to send a PR that looks for a causer interface I'll take it.

Oh you did already. :-)