[vikeri]

One thing that seemingly is missing is the ability to tag a specific error with an error code. You typically want to know that all of a sudden the ”failed to get user” error is being returned a lot. Since the message is a dynamic string you can’t just group by the string so unless you build it as part of your abstraction it becomes very hard to do.

Edit: looking more carefully at the lib I assume that ”tag” is the concept that is supposed to cover this?

[arccy]

in standard go you'd have errors implement:

    func (myError) Is(err error) bool

and it can match different sentinel errors. Or you can make your own wrapper to have the error chain match.

[zarldev]

In standard go you would not implement Is but would use the errors.Is call. How would this work if it is a sentinel error as you would use with errors.Is??

[arccy]

https://pkg.go.dev/errors#Is

> An error is considered to match a target if it is equal to that target or if it implements a method Is(error) bool such that Is(target) returns true.

by default errors.Is matches the exact error variable, but you can use it to match other errors as well.

[zarldev]

I stand corrected. Still you cannot implement an Is on a sentinel error and is only applicable to concrete error types. And if I'm using concrete types I'm going to us errors.As