[Haskell-cafe] RFC: in haddock, collapse instances by default

[Nathan Collins]

* I think collapsing instances by default is a great idea! +1

* Examples are already collapsed by default, and I think instances
should be treated the same way.

Re the concern that this would make the Servant docs worse, for me it
would just be a matter of knowing to expand the instance docs when I'm
interested in the corresponding class, the same way I expand the
examples only where I'm interested.

Here's an example of instance docs in Servant:
http://hackage.haskell.org/package/servant-0.15/docs/Servant-API.html#t:FromHttpApiData.
Until I'm interested in the FromHttpApiData class, I don't personally
want to see that long list of instances with some examples. Also, in
my experience, having lots of docs/examples on the instances like this
is not very common.

Here's an instance of examples being collapsed by default to good
effect in the Prelude docs for Either:
https://hackage.haskell.org/package/base-4.12.0.0/docs/Prelude.html#t:Either

* Having a "collapse all/expand all" toggle at the top of the page
would be nice, but if the default is not "collapsed" then I'd want a
way to make that my personal default.

I don't know much about web development, but my impression is that we
could use a cookie and some simple JavaScript [1] to make "collapse by
default" a per-user preference, say by remembering the last state of
the hypothetical "collapse all/expand all" toggle button at the top.
Haddock already uses JavaScript, so I expect this would be a small
addition.

Cheers,

-nathan

[1] https://developer.mozilla.org/en-US/docs/Web/API/document/cookie

On Wed, Jan 2, 2019 at 11:23 PM Oleg Grenrus <oleg.grenrus at iki.fi> wrote:
>
> How about a compromise: show dozen or so instances with "show rest" link-toggle. That would work very nicely, if we could control which instances (e.g. instances with haddocks) should be shown.
>
> E.g. in `servant` *a lot* of docs & examples are in instance haddocks, so making them hidden will make documentation strictly worse.
>
> - Oleg
>
> On 3 Jan 2019, at 7.50, Ryan Reich <ryan.reich at gmail.com> wrote:
>
> I think this is a great idea.  I do wonder, however, if it might exacerbate a kind of meta-documentation problem that I, at least, had when I was more of a beginner: it was not clear to me that most of a type's API is implicit in its instances of many standard classes, and specialized functions for things like mapping or folding or appending may not even be present in the rest of the module.  Obviously this is something that every Haskeller needs to learn, but it was an issue for me even when the instance lists were present for me to gloss over.
>
> Perhaps Haddock could, rather than establishing this as a new default, provide a "collapse all" and "expand all" set of functions at the top of the page?
>
> On Wed, Jan 2, 2019 at 8:03 PM Li-yao Xia <lysxia at gmail.com> wrote:
>>
>> Hello Café,
>>
>> I would like to propose making haddock keep instance lists collapsed by
>> default. Some discussion is in order since it would significantly affect
>> the documentation of many packages on Hackage.
>>
>> Feel free to reply here or on the related Github thread:
>> https://github.com/haskell/haddock/issues/698
>>
>> 1. Instance lists take a lot of screen estate
>>
>> For a motivating example, I can point to the Prelude we all love.
>>
>> https://hackage.haskell.org/package/base-4.12.0.0/docs/Prelude.html
>>
>> We are immediately welcomed by half a page of instances of Bool, which
>> is not quite bad, but classes have the most impressive instance lists,
>> as you may see when you reach Eq.
>>
>> Many packages, even commonly used ones, have the same issue. For an
>> extreme example, see the scrollbar jump when you fold the instance list
>> of Apply in singletons.
>>
>> https://hackage.haskell.org/package/singletons-2.5.1/docs/Data-Singletons.html#t:Apply
>>
>> 2. Current workarounds
>>
>> They can be collapsed manually one by one, and we can jump to the middle
>> of a module with the table of contents, but scrolling up from the bottom
>> of an instance list is still a chore.
>>
>> Of course, instance lists also contain quite important information.
>> Would it become too easy to miss if it were hidden by default? Would a
>> more fine-grained alternative be better?
>>
>> Regards,
>> Li-yao
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