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* Should the HTML writer generate empty '<span>' elements?
@ 2021-09-04 16:08 Gwern Branwen
       [not found] ` <CAMwO0gywhE+u4wgaL0sieohjuqAm+VM2Lj489EsQST74FMqrMA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
  0 siblings, 1 reply; 4+ messages in thread
From: Gwern Branwen @ 2021-09-04 16:08 UTC (permalink / raw)
  To: pandoc-discuss

While working on cleaning up & debugging my smallcaps/<wbr> code I
noticed again that Pandoc will compile empty Span Inline nodes to
empty HTML '<span></span>' (or just '<span />') elements. Is there any
reason Pandoc should do this?

Example:

    $ echo 'Span ("",[],[]) []' | pandoc -f native -w html
    <span></span>

(Hakyll seems to render that as a self-closed '<span />' somewhere in
the pipeline, but same thing.)

The reasons not to are that an empty Span would appear to be
meaningless, since it cannot style or wrap any *span* of text. As
there is nothing in it, it cannot be styled easily by CSS (you could
write CSS rules which affect it but I think only by selecting on all
span elements by either class or possibly position, which would
seriously screw up regular useful spans since whatever you were doing
to the empty span would affect them too, and so I guess you'd have to
negate every single class or position you *didn't* want to affect?).
Since there is no reasonable use I can come up with, that implies an
empty span is probably an error by the user or Pandoc somewhere, which
would be a good reason to warn/error about it.

Further, it is possibly buggy. Empty spans appear to confuse and
enrage various tools (although I haven't found any statement that it
is outright illegal by any standards); the W3C HTML checker is
extremely unhappy about empty self-closed spans*, Firefox's
view-source parses it in strange ways, empty spans appeared to cause
issues with my auto-smallcaps rendering the entire following paragraph
in smallcaps as well until hitting a </p> implicitly closing the span
run amok, ckeditor removes empty spans by default
(https://github.com/ckeditor/ckeditor4/issues/2484), and HTML Tidy
both warns about & outright deletes empty spans when reformatting.**

So, do any Pandoc users ever use completely empty spans? Empty spans
but with IDs or classes or attributes? Empty spans in any context
whatsoever? Can you come up with any legitimate reason that the HTML
writer should generate empty spans?

If not, then I'll file a bug about suppressing empty spans.

* The W3C validator errors for '<span />':

    Error: Self-closing syntax (/>) used on a non-void HTML element.
Ignoring the slash and treating as a start tag.
    From line 152, column 1; to line 152, column 8
    d>↩<body>↩<span />↩</bod

    Error: End tag for body seen, but there were unclosed elements.
    From line 153, column 1; to line 153, column 7
    ↩<span />↩</body>↩</htm

    Error: Unclosed element span.
    From line 152, column 1; to line 152, column 8
    d>↩<body>↩<span />↩</bod
** Tidy output:

    $ echo 'Span ("",[],[]) []' | pandoc --standalone -f native -w
html | tidy  -errors --doctype html5
    [WARNING] This document format requires a nonempty <title> element.
      Defaulting to '-' as the title.
      To specify a title, use 'title' in metadata or --metadata title="...".
    line 2 column 1 - Warning: <html> attribute "lang" lacks value
    line 152 column 1 - Warning: trimming empty <span>
    Info: Document content looks like XHTML5
    Tidy found 2 warnings and 0 errors!

-- 
gwern
https://www.gwern.net

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^ permalink raw reply	[flat|nested] 4+ messages in thread
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2021-09-04 16:08 Should the HTML writer generate empty '<span>' elements? Gwern Branwen
     [not found] ` <CAMwO0gywhE+u4wgaL0sieohjuqAm+VM2Lj489EsQST74FMqrMA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2021-09-04 22:49   ` MarLinn
     [not found]     ` <543ae04c-c5ef-99c3-cff7-15068893b3e4-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2021-09-04 23:15       ` Gwern Branwen
     [not found]         ` <CAMwO0gyKnt3aaaGqM_D61ttQOM0v4iz2uHM3RtW9pgkiO+fWXg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2021-09-05  0:51           ` MarLinn

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