[R-pkg-devel] Package Anchored Links with R-Dev

[Duncan Murdoch]

On 09/08/2020 3:15 p.m., Ben Bolker wrote:
> 
> On 8/9/20 3:08 PM, Duncan Murdoch wrote:
>> On 09/08/2020 2:59 p.m., John Mount wrote:
>>> Firstly: thanks to Ben for the help/fix.
>>>
>>> I know nobody asked, but.
>>>
>>> Having to guess where the documentation is just to refer to it is
>>> just going to be really brittle going forward. Previous: if the
>>> function you referred to existed in the package you were fine.
>>
>> That's not correct.  The system could often work around the error, but
>> not always.
> 
>     I may be missing something. It may well be that referring to a
> cross-package link by alias rather than by the name of the Rd page
> actually never worked, but: would there be a big barrier to making
> cross-package documentation links be able to follow aliases? I can
> imagine there may be technical hurdles but it seems like a well-defined
> problem ...

To link to "?utils::dump.frames", you need to construct a URL that leads 
to the HTML file containing that help page on static builds of the help 
system.

If utils is available, no problem, just look up the fact that the page 
you want is debugger.html at the time you construct the link.  But it 
was documented that such links should work even if the target package 
was not available at the time the link was being made.  So you need a 
link that you are sure will be available when the referenced package is 
eventually installed.  Obviously that's going to be brittle.

Perhaps the new requirement that referenced packages be mentioned in the 
DESCRIPTION file is a step towards addressing this.  If everything 
that's referenced is present when the help system is being built, there 
will be an easy solution.

Nowadays, it would probably be reasonable to put in stub pages for every 
alias, so that when you try to load dump.frames.html, the page itself 
redirects you to debugger.html.  Or maybe you could just have a single 
page in each package that handles aliases via Javascript.

Or R could just no longer support static copies of the help system.

When you are using dynamically generated help pages, the link can be 
resolved by the server, and that's why those links have appeared to work 
for so long, even though the requirement to link to the filename instead 
of the alias has been there since before I wrote the dynamic help server.

Duncan Murdoch

> 
> 
>>
>> Duncan Murdoch
>>
>>
>>   Future: if don't correctly specify where the help is you are wrong.
>> Going forward: reorganizing a package's help can break referring
>> packages. This sort of brittleness is going to be a big time-waster
>> going forward. It seems like really the wrong direction in packaging,
>> isolation, and separation of concerns (SOLID style principles).
>>>
>>>> On Aug 9, 2020, at 11:04 AM, Ben Bolker <bbolker using gmail.com> wrote:
>>>>
>>>> This might have to be \link[utils:debugger]{dump.frames} now, i.e.
>>>> explicitly linking to the man page on which dump.frames is found
>>>> rather than following aliases?
>>>>
>>>> On Sun, Aug 9, 2020 at 2:01 PM John Mount <jmount using win-vector.com>
>>>> wrote:
>>>>>
>>>>> With "R Under development (unstable) (2020-07-05 r78784)" (Windows)
>>>>> documentation references such as "\link[utils]{dump.frames}"
>>>>> trigger "Non-file package-anchored link(s) in documentation object"
>>>>> warnings even if the package is in your "Imports."
>>>>>
>>>>> Is that not the right form? Is there any way to fix this other than
>>>>> the workaround of just removing links from the documentation? I
>>>>> kind of don't want to do that as the links were there to help the
>>>>> user.
>>>>>
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>>