We are a team of experienced developers and are currently discussing how we
may improve our modeling of expected domain errors in our layered
architecture. We are used to work with the idiomatic way of defining and
matching against our custom error types. We followed and understand the
design decisions of the error interface and its usage within the standard
library. However, we are yet dissatisfied with our developer experience due
to the limited expressiveness. For example, it is quite common to oversee a
mapping case of an infrastructure error into a domain error. It is clear,
that we try to document our "error sum type" but without bothering the
compiler, that is just not helpful enough.
So we are now considering to define custom error interfaces with marker
methods to represent a sealed set of domain errors. The intention is to
create the most type safe coupling for error handling, which the Go
compiler can guarantee - just like we do with regular parameter types. We
don't need (or want) covariant result types here. And by still using an
interface, we also avoid the interface-type-not-nil edge case.
*I'm wondering how others deal with this in practice. *
*Are there any experience reports? *
Example
// CalculationError defines a sealed set of multiple domain error types
type CalculationError interface{
error
failedCalculation()bool
}
//...
// ApplyCalculation is more specific about the error and violates
intentionally idiomatic go but
// we have a tight coupling anyway.
func ApplyCalculation(p SomeDomainType)(SomeDomainResult, CalculationError){
//...
}
related discussions (excerpt)
- https://go.dev/blog/error-handling-and-go
- https://go.dev/blog/go1.13-errors
- https://github.com/golang/go/issues/19412#issuecomment-1464178165
- https://dave.cheney.net/2014/12/24/inspecting-errors
-
https://dave.cheney.net/2016/04/27/dont-just-check-errors-handle-them-gracefully
- https://blog.merovius.de/posts/2018-01-21-what_even_is_error_handling/
- ...
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