Re: Maintaining implementations of similar utility functions like json-fetch

[Catonano <catonano@gmail.com>]

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2018-01-31 18:32 GMT+01:00 Jelle Licht <jlicht@fsfe.org>:

> Hi Ludo',
>
>
> 2018-01-27 17:09 GMT+01:00 Ludovic Courtès <ludo@gnu.org>:
>
>> Hello!
>>
>> Jelle Licht <jlicht@fsfe.org> skribis:
>>
>> > I noticed that there are currently two very similar functions for
>> fetching
>> > json data; `json-fetch' in (guix import json) and `json-fetch*' in (guix
>> > import github).
>> >
>> > Some things I noticed:
>> > - Dealing with http error codes seems to be a bit more robust in
>> > `json-fetch*'.
>> > - Making sure that (compliant) servers give responses in the proper
>> format
>> > seems more robust in `json-fetch' due to using Accept headers.
>> > - Dealing with the fact that json responses are technically allowed to
>> be
>> > lists of objects, which `json-fetch' does not handle gracefully.
>> >
>> > For this issue specifically, would it make sense to combine the two
>> > definitions into a more general one?
>>
>> Definitely, we should just keep one.  It’s not even clear how we ended
>> up with the second one.
>>
>
> I even had a third one in my local tree which happened to have a conflict,
> which
> is how I found out in the first place, so I understand how these things
> can happen.
>
>>
>> > My more general concern would be on how we can prevent bug fixes only
>> being
>> > applied to one of several nearly identical functions. IOW, should we
>> try to
>> > prevent situations like this from arising, or is it okay if we somehow
>> make
>> > sure that fixes should be applied to both locations?
>>
>> We should prevent such situations from arising, and I think we do.
>>
>> The difficulty is that avoiding duplication requires knowing the whole
>> code base well enough.  Sometimes you just don’t know that a utility
>> function is available so you end up writing your own, and maybe the
>> reviewers don’t notice either and it goes through; or sometimes you need
>> a slightly different version so you duplicate the function instead of
>> generalizing it.
>>
>> Anyway, when we find occurrences of this pattern, we should fix them!
>>
>
> I basically added the robust features of `json-fetch*' to the exported
> `json-fetch'
> instead, and all existing functionality seems to work out as far as I can
> see.
>
> I did notice that I now produce hash-tables by default, and some of the
> existing usages of `json-fetch*' expect an alist instead. What would be a
> guile-
> appropriate way of dealing with this? I currently have multiple
> `(hash-table->alist (json-fetch <...>))' littered in my patch which seems
> suboptimal,
> but always converting the parsed json into an alist seems like it might
> also not be
> what we want.
>

of course I' d wait for a thought by some more competent guiler,  but I' d
like to offer my take on this

The new function could take one further argument, a boolean

If the boolean is true, it could return a hash table

Otherwise, it could return a list

If the majority of call sites expect a list, the further argument could set
to false as default

So you' d only have to fix those call sites that want a hash table instead

If, instead, the majority of call sites want a hash table, your procedure
would return a hash table by default and a list by a further argument, so
you' d have to fix a minority of call sites anyway

I hope I didn' t make myself a fool :-/


> Thanks,
> Ludo’.
>

> - Jelle
>

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