Re: [PATCH 04/23] qapi: expand tags to all doc sections

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> On Fri, Dec 20, 2024, 8:13 AM Markus Armbruster <armbru@redhat.com> wrote:
>
>> John Snow <jsnow@redhat.com> writes:
>>
>> > This patch adds an explicit section tag to all QAPIDoc
>> > sections. Members/Features are now explicitly tagged as such, with the
>> > name now being stored in a dedicated "name" field (which qapidoc.py was
>> > not actually using anyway.)
>> >
>> > WIP: Yeah, the difference between "tagged" and "untagged" sections is
>> > now pretty poorly named, and explicitly giving "untagged" sections an
>> > "UNTAGGED" tag is ... well, worse. but mechanically, this accomplishes
>> > what I need for the series.
>> >
>> > Please suggest better naming conventions, keeping in mind that I
>> > currently have plans for a future patch that splits the "UNTAGGED" tag
>> > into "INTRO" and "DETAILS" tags. But, we still need a meta-name for the
>> > category of sections that are "formerly known as untagged" but cannot be
>> > called "freeform" because that name is used for the category of
>> > docblocks that are not attached to an entity (but happens to be
>> > comprised entirely of "formerly known as untagged" sections.)
>> >
>> > Signed-off-by: John Snow <jsnow@redhat.com>
>>
>> A free-form doc comment consists of just one untagged section, actually.
>> I don't remember whether anything relies on "just one".
>>
>
> Sure, yes. Sorry, I keep thinking of documentation as containing "any
> number of sections" but keep eliding the fact that our parser
> implementation currently will never actually create multiple adjacent
> "untagged" sections.

Yes, the parsers grows an untagged section until another section starts.
An untagged section can consist of multiple paragraphs, just like tagged
sections.

> I don't even change this anywhere even in my offline WIP, so it's just me
> being over-general.
>
> (I don't think it winds up being relevant or mattering to anything in this
> series or my larger project beyond some word choices.)
>
>> The term "tagged" is rooted in doc comment syntax.
>> docs/devel/qapi-code-gen.rst section "Definition documentation":
>>
>>     Definition documentation starts with a line naming the definition,
>>     followed by an optional overview, a description of each argument (for
>>     commands and events), member (for structs and unions), branch (for
>>     alternates), or value (for enums), a description of each feature (if
>>     any), and finally optional tagged sections.
>>
>> Sadly, this isn't fully accurate anymore.
>>
>>     Descriptions start with '\@name:'.  The description text must be
>>     indented [...]
>>
>>     A tagged section begins with a paragraph that starts with one of the
>>     following words: "Since:", "Returns:", "Errors:", "TODO:".  It ends
>> with
>>     the start of a new section.
>>
>>     The second and subsequent lines of tagged sections must be indented
>>     [...]
>>
>> Nothing about untagged sections.  These are sections that aren't
>> descriptions or tagged.  Example:
>>
>>     # @Returns: Lorem ipsum dolor sit amet, consectetur adipiscing elit,
>>     #     sed do eiusmod tempor incididunt ut labore et dolore magna
>>     #     aliqua.
>>     #
>>     # Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris
>>     # nisi ut aliquip ex ea commodo consequat.
>>     #
>>     # Duis aute irure dolor in reprehenderit in voluptate velit esse
>>     # cillum dolore eu fugiat nulla pariatur.
>>     ##
>>
>> Here, the tagged "Returns" section ends after "aliqua."  Why?  Because
>> "Ut enim" isn't indented.  The untagged section ends after "pariatur."
>>
>> We parse a definition doc comment as a sequence of sections.
>>
>> The first one is the overview.
>>
>> Member / argument descriptions, if any, are next.
>>
>> Then we may have any number of tagged or untagged sections.  If I
>> remember correctly, you'd like to banish them.  Let's pretend they can't
>> exist here.
>>
>
> I think you're referring to my desire to banish "untagged" sections from
> appearing *between* "tagged" sections.

Editing accident, sorry!  You interpreted it correctly.

>                                        Yes, that's still a desire; though I
> make no movement on it in this series as sent to list, and this change is
> entirely unrelated to that desire.
>
> (It's more related to being able to distinguish features from members, and
> later, distinguishing intro/details. This patch still serves a purpose even
> without the inliner or the complexities it brings, but serves both needs.)
>
> ((Reminder: the reason for this desire is because "tagged sections" are
> rendered in html as a two-column list, and free paragraphs appearing
> between list entries looks bad in the rendered documentation, because it
> means ending the table, starting paragraph(s), then starting a new table.
> If free text is meant to be associated with a specific
> member/feature/section-group, it should be marked up (in SOME way) so that
> the renderer can achieve that grouping visually.
>
> (There will be a standalone patch that implements this restriction and we
> can debate this there, I'm only giving you context here.)))
>
>
>> Then we may have a "Features:" line followed by feature descriptions.
>>
>> Finally, we may have any number of tagged or untagged sections.
>>
>> Each of these sections is represented as an instance of type Section,
>> and the entire definition doc as an instance of type QAPIDoc.
>>
>> Section has a member @tag of type str.
>>
>> For tagged sections, it's the tag, i.e "Since", "Returns", ...  Obvious
>> enough.
>>
>> For overview and other untagged sections, it's None.  Still obvious.
>>
>> For descriptions, it's the name of the thing being described.  Less than
>> obvious.  Note that descriptions are actually instances of ArgSection, a
>> subtype of Section, which prevents confusion with tagged sections.
>>
>
> Note that this patch changes this as well; it becomes "member" or "feature"
> as appropriate and the name is moved into a dedicated name field that
> belongs to the ArgSection class.
>
> (Turns out legacy qapidoc doesn't use this stored name at all anyway, it
> fetches the name via the linked feature/member instead.)
>
>
>> QAPIDoc has the overview in member @body, member / argument descriptions
>> in @args, feature descriptions in @features, and the remaining sections
>> in @sections.
>>
>> I'm in favor of cleaning this up some.
>>
>> I think we can keep the Section name.
>>
>> Moving the name of the thing being described from @tag to @name is good.
>> What value to put into @tag then?  Whatever suits you.
>>
>
> What suits me is "member" and "feature". :)

Okay.

Doesn't entirely clean up the terminology mess.  According to
docs/devel/qapi-code-gen.rst, struct and union types have members,
alternate types have alternatives, enum types have values, commands have
arguments, and events have event-specific data, which is a mouthful, so
we often say arguments.  Using one of them ("member") to refer to the
generalization of them all is suboptimal, but it's no worse than before.

ArgSection is even more general: it's features, too.  Again, no worse
than before.

I'm *not* asking you to clean this up.  I'm just pointing out we could
use fresh naming ideas here.

>> Perhaps we should rename @tag to avoid undue ties to tagged sections.
>> @kind would work for me.
>>
>
> Sold!
>
>
>> Value None for untagged sections is fine with me.  If a string suits you
>> better, that's fine, too.  "untagged", "plain", I don't know, propose
>> something.
>>
>
> For static typing reasons, an explicit tag is preferred to distinguish from
> it being "optional".
>
> I could cope with any of:
>
> "plain",
> "text",
> "plaintext",
> "paragraphs",
> "unstructured",
> "free"
>
> ... keeping in mind that I do intend to "split" this tag/kind into "intro"
> and "details" later. i.e. this is a temporary tag/kind label.
>
> I think I like "text" the most because it says the least. What about you?

Point, but the other kinds of section are text, too.  "plain"?

>> @body, @args, and so forth aren't exactly great names.  If they truly
>> annoy or confuse you, feel free to propose better ones.
>>
>
> I believe they can be removed entirely once the old qapidoc is sunset,
> leaving only .sections[] behind.
>
> This removes the temptation to pick out sections "out of order".

I've long wanted strict in-order processing, to avoid surprising
reordering of input in the output.

> We only need the list of sections in their source order to generate the
> appropriate rST.
>
> (Note: the inliner actually does need to filter sections somewhat to do its
> inlining magic, but we'll talk about that later. All you need to know right
> now is that my WIP does not utilize any field except .sections[], so the
> others can in fact be dropped as redundant once we make the switch. This
> patch helps enable the paradigm of "everything you need to render a section
> is contained within the Section object itself" which lends itself well to
> the new transmogrifier, the goal of always processing/rendering in source
> order, and facilitating the mechanics of the inliner.)
>
> ...
>
> In case I got too rambly, my action items for this patch are:
>
> - fix the test (already done)
> - rename tag to kind
> - rename "untagged" to "text", possibly changing it again pending your
> feedback.

Sounds good!