Re: discrepancy between groff and mandoc for html rendering of wg-quick(8)

[Ingo Schwarze <schwarze@usta.de>]

Hi Jan, hi Jason,

Jan Stary wrote on Wed, Feb 12, 2020 at 08:02:29AM +0100:
> On Feb 11 23:59:21, Jason@zx2c4.com wrote:

>> [mandoc] https://manpages.debian.org/testing/wireguard-tools/wg-quick.8.en.html

> That is not the output of mandoc -Thmtl as such.
> That's mandoc's html output inset into a debian webpage.

While that is true, it is not really relevant.

The OP did find a bug in mandoc, which you can see by comparing the
output from the following two commands, even with mandoc -current:

   $ printf "A\n.br\nB\n" | mandoc -T html
   $ printf "A\n.br\n B\n" | mandoc -T html

In the second case, the <br/> element is missing between the "A" and the "B",
even though in terminal output mode (i.e. without the -T html), the line
break is correctly emitted in both cases.

A first superficial inspection reveals that the validation module is
probably making invalid assumptions that leading whitespace on an input
line automatically implies a line break for all output modes, which is
not true for HTML.

I'll need to have a closer look how to fix this; i'm not yet sure whether
the validator or the formatter or both need to be changed.

>> [groff] https://git.zx2c4.com/wireguard-tools/about/src/man/wg-quick.8

> That is not the output of gorff -Thmtl -mman either.
> That's groff's html output inset into a webpage.

Again, not really relevant.  It does show that groff respects the .br
request, which, of course, is not surprising at all.

>> Look at the "EXAMPLES" section. Notice weird line break issues with mandoc.
>> Is this a man page source bug or a mandoc bug?
>> Source is here: https://git.zx2c4.com/wireguard-tools/tree/src/man/wg-quick.8

> Take that source, produce the two html outputs
> 
> 	mandoc -Thtml wg-quick.8 > wg.mandoc.html
> 	groff  -Thtml -mman wg-quick.8 > wg.groff.html
> 
> and compare the results. They are different,
> but none has the line breaks in EXAMPLES.

According to my testing, "groff -Thtml -mman wg-quick.8"
does produce the expected line breaks, e.g.:

  [...]
  <h2>EXAMPLES
  [...]
  <p style="margin-left:11%; margin-top: 1em">[Peer] <br>
  PublicKey = GtL7fZc/bLnqZldpVofMCD6hDjrK28SsdLxevJ+qtKU=
  <br>
  PresharedKey = /UwcSPg38hW/D9Y3tcS1FOV0K1wuURMbS0sesJEP5ak=
  <br>
  AllowedIPs = 0.0.0.0/0 <br>
  Endpoint = demo.wireguard.com:51820</p>

I think we are talking about the <br> lines before and after "PresharedKey",
for example.

So the bug report is clearly valid and also precise enough to help
me fix it.

Thanks for the report,
  Ingo
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