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Re: ref-filter: how to improve the code




2018-02-28 16:25 GMT+03:00 Jeff King <peff@xxxxxxxx>:
> 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).

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).

>
>> 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