On Tue, Feb 15, 2022 at 5:49 AM Vojtěch Bargl <bargl.vojt...@gmail.com> wrote:
>
> my name is Vojta and I would like to join a error handling proposals
> discussion and because I don't know what else to say I guess I will jump
> right to it.
>
> I know everyone has his/her own opinion about this topic, which has its pros
> and cons.
> And even though I think current solution is well-done I found myself smiling
> when I browse through my or someone else's source code because of that very
> well known reoccurring pattern:
> ```
> if err != nil { ... }
> ```
> Do not get me wrong but I think it is pretty ironic when you see reoccurring
> pattern in context where you try to minimize these into more generalized form.
>
> I tried to read most issues on Github with error-handling label, but there
> are just so many that in this point I am glad I found link to Error Handling
> meta issue which summarize all important issues about this topic. I would
> like to get your opinion about solution that I did not find in this
> summarized list.
>
> I would like to get opinion of people that know little more about golang
> itself and are able to provide "holes" in this solution. Feel free to point
> them out, but please keep in mind that I may not be able to solve them alone.
> Like I said, I just wanted to discuss this solution before I file official
> issue proposal.
>
> Solution
> I got inspired with golangs `:=` operator that handles declaration and
> assignment of variable. It's basically two operations in one. So what about
> using something similar, like `?=`, that would assign variables and
> additionally check if last variable (if error) is not nil?
>
> What I'm talking about is replace these lines:
> ```
> if value, err = ReturnValueAndErr(); err != nil {
> goto Err
> }
> if otherValue, err = DeriveAnotherValueAndErr(value); err != nil {
> goto Err
> }
>
> Err:
> // handle errors
> ```
>
> with these lines:
> ```
> value, err ?= ReturnValueAndErr()
> otherValue, err ?= DeriveAnotherValueAndErr(value)
>
> error:
> // handle error
> ```
>
> It's very short and seems idiomatic to golang and it's main feature is it
> does not break the flow of thought that author tried to express. Error
> handling itself is already defined (and used) feature - labels and name of
> label is intentionally already known keyword to get the link between ?=
> operator and error handling.
>
> There are few limitations though:
>
> variables needs to be declared before
> (I mean not really, but idea is to access assigned variables in label.
> so value, otherValue and err should be declared)
> label error must exists and serve only this purpose
> (compiler option could change the name for backward compatibility)
>
> So what do you say?
> Can you make it better?
The idea of doing an automatic goto on error is also an aspect of
https://go.dev/issue/32611
https://go.dev/issue/34140
https://go.dev/issue/37035
There is a subtle complexity to such proposals. The current Go
language does not permit a goto statement if there are new variables
in scope at the goto label but not at the goto statement
(https://go.dev/ref/spec#Goto_statements). But this is hard to avoid
with a scheme like the one presented here. How do we handle that
while retaining backward compatibility?
Ian
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