Py, use more desc_sig_* nodes

[jakobandersen]

Feature or Bugfix

• Feature
• Bugfix?
• Refactoring

Purpose

A continuation of #9023, changing many parts of the Python domain to use more of the addnodes.desc_sig_* nodes for markup. This especially includes the use of the space node to make sure spaces are not swallowed if themes use alternative CSS (#9599).

Detail

All of the changes are relatively simple, but it is not complete: the whole pendinx_xref handling is a bit more complicated than I dare to touch right now.

TODO and Context

• Any semi-trivial places I missed?
• Probably for another PR: the pending_xref`' handling. It seem like a name A.B.Cbecomes a single xref with the content being anodes.Tex``.
  I think it would be good to change it to something like a
  1. pending_xref with target A and content desc_sig_name with A
  2. . as punctuation
  3. pending_xref with target A.B and content desc_sig_name with B
  4. . as punctuation
  5. pending_xref with target A.B.C and content desc_sig_name with C
• For another PR: write some documentation for how to style domain elements in HTML
• For another PR: work around the <span class="pre"> wrapping in
  

  sphinx/sphinx/writers/html.py

  Line 709 in 699d03f

  self.body.append('<span class="pre">%s</span>' % token)

  and

  sphinx/sphinx/writers/html5.py

  Line 645 in 699d03f

  self.body.append('<span class="pre">%s</span>' % token)

Relates

• Continuation of Flexible declaration styling #9023
• Fixes some parts of Add an option to not create links within a sig-param block #9599 (ping @mattip)
• Perhaps fixes some of Provide better CSS selectors for API-documentation content #9663? (ping @pradyunsg)

[jakobandersen]

While the use of nodes is undocumented this may still break some themes, so perhaps there should be an "incompatible changes" entry as well?

[tk0miya]

LGTM with nits.

Any semi-trivial places I missed?

It seems OK. Let's fix them if we'll find them later.

While the use of nodes is undocumented this may still break some themes, so perhaps there should be an "incompatible changes" entry as well?

I think side effects are nothing or very less. But I'm not sure nobody gives styles to these classes. So it would be better to mention it.

[tk0miya]

LGTM with nits. Please merge this after fixing the typo.