bug#74785: 27.1; Fill-paragraph in RST mode does not respect line blocks

[Richard Brooksby <rb@ravenbrook.com>]

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On 2024-12-17 17:12, Stefan Monnier wrote:
>>> - set `adaptive-fill-regexp` to match this leading `|`.
>> Doesn't it already?
> 
> Not in my test, no.  With a paragraph like:
> 
>      | bblblbl
>      | asdfasdf
>      | asdasdf

Please find attached a self-documenting test document that you may find 
useful.

Thank you!

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================
 Bug 74785 test
================

This is a test file for `GNU Emacs bug 74785
<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=74785>`_, created to
help clarify the issue and help developers test solutions.  It's not
exhaustive.

You can check the output easily with rst-compile (C-c C-c C-c).

It would be nice if selecting the *entire* document and executing
fill-paragraph would result in a document that is:

1. filled and wrapped nicely as a text source

2. has unchanged output.

Example one.  In the simple case, as a top-level block.

| In Xanadu did Kubla Khan
| A stately pleasure-dome decree:
| Where Alph, the sacred river, ran
| Through caverns measureless to man
| Down to a sunless sea.

Example two.  Here's the same thing as a quote.

  | In Xanadu did Kubla Khan
  | A stately pleasure-dome decree:
  | Where Alph, the sacred river, ran
  | Through caverns measureless to man
  | Down to a sunless sea.

  -- Samuel Taylor Coleridge

Example three.  With continuation lines, this should produce identical
output to the previous example.

  | In Xanadu did Kubla Khan
  | A stately
    pleasure-dome
    decree:
  | Where Alph,
    the sacred river,
    ran
  | Through caverns
                measureless to man
  | Down to a sunless sea.

  -- Samuel Taylor Coleridge

It would be nice if fill-paragraph (M-q) would reformat example three
to look like example two.

Example four.  Conversely, here's a verse with long lines beyond the
default fill column of 70.

  | Begins the night’s shadows creeping, his eyes mocking, and beseeching.
  | I must stop his soul from joining, to fight with Poes’ shadows trying…
  | Trying once more, to take his soul, toward those demon littered shores.
  | Grabbing the ipod I forward tore, to give him tranquility evermore. 
  | Pouch and ear buds firmly seated, engaged in a fierce-some war.
  | Morning found all, in blissful snores… Quoted the raven nevermore.

  -- Carol Eastman

Example five.  It would be nice if fill-paragraph would wrap these
lines, but in a way that keeps the output identical.  For example
(with fill-column 70):

  | Begins the night’s shadows creeping, his eyes mocking, and
    beseeching.
  | I must stop his soul from joining, to fight with Poes’ shadows
    trying…
  | Trying once more, to take his soul, toward those demon littered
    shores.
  | Grabbing the ipod I forward tore, to give him tranquility
    evermore.
  | Pouch and ear buds firmly seated, engaged in a fierce-some war.
  | Morning found all, in blissful snores… Quoted the raven nevermore.

  -- Carol Eastman

Of course all of the above must work when nested within other forms.

Thanks all.

.. end