ref-filter: how to improve the code

> I am trying to remove cat-file formatting part and reuse same
> functionality from ref-filter.
> I have a problem that cat-file sometimes needs to continue running
> even if the request is broken, while in ref-filter we invoke die() in
> many places everywhere during formatting process. I write this email
> because I want to discuss how to implement the solution better.
> 
> ref-filter has 2 functions which could be interesting for us:
> format_ref_array_item() and show_ref_array_item(). I guess it's a good
> idea to print everything in show_ref_array_item(), including all
> errors. In that case all current users of ref-filter will invoke
> show_ref_array_item() (as they did it before), and cat-file could use
> format_ref_array_item() and work with the result in its own logic.

> One of the easiest solutions is to add strbuf parameter for errors to
> all functions that we use during formatting process, fill it in and
> print in show_ref_array_item() if necessary. What do you think about
> this idea?
> 
> Another way is to change the resulting error message, print current
> message with "error" prefix and then print something like "fatal:
> could not format the output". It is easier but I am not sure that it's
> a good idea to change the interface.

> On Sun, Feb 25, 2018 at 09:28:25PM +0300, Оля Тележная wrote:
>
>> I am trying to remove cat-file formatting part and reuse same
>> functionality from ref-filter.
>> I have a problem that cat-file sometimes needs to continue running
>> even if the request is broken, while in ref-filter we invoke die() in
>> many places everywhere during formatting process. I write this email
>> because I want to discuss how to implement the solution better.
>>
>> ref-filter has 2 functions which could be interesting for us:
>> format_ref_array_item() and show_ref_array_item(). I guess it's a good
>> idea to print everything in show_ref_array_item(), including all
>> errors. In that case all current users of ref-filter will invoke
>> show_ref_array_item() (as they did it before), and cat-file could use
>> format_ref_array_item() and work with the result in its own logic.
>
> Yes, that arrangement makes sense to me.
>
>> I tried to replace all die("...") with `return error("...")` and
>> finally exit(), but actual problem is that we print "error:..."
>> instead of "fatal:...", and it looks funny.
>
> If you do that, then format_ref_array_item() is still going to print
> things, even if it doesn't die(). But for "cat-file --batch", we usually
> do not print errors at all, but instead just say "... missing" (although
> it depends on the error; syntactic errors in the format string would
> still cause us to write to stderr).

>
>> One of the easiest solutions is to add strbuf parameter for errors to
>> all functions that we use during formatting process, fill it in and
>> print in show_ref_array_item() if necessary. What do you think about
>> this idea?
>>
>> Another way is to change the resulting error message, print current
>> message with "error" prefix and then print something like "fatal:
>> could not format the output". It is easier but I am not sure that it's
>> a good idea to change the interface.
>
> For reference, the first one is what we've been switching to in the refs
> code. And I think it's been fairly successful there.
>
> -Peff

> >> I tried to replace all die("...") with `return error("...")` and
> >> finally exit(), but actual problem is that we print "error:..."
> >> instead of "fatal:...", and it looks funny.
> >
> > If you do that, then format_ref_array_item() is still going to print
> > things, even if it doesn't die(). But for "cat-file --batch", we usually
> > do not print errors at all, but instead just say "... missing" (although
> > it depends on the error; syntactic errors in the format string would
> > still cause us to write to stderr).
> 
> Not sure if you catch my idea. format_ref_array_item() will not print
> anything, it will just return an error code. And if there was an error
> - we will print it in show_ref_array_item() (or go back to cat-file
> and print what we want).