Re: [bug] `org-latex-line-break-safe' breaks the export of verse blocks to LaTeX

[Max Nikulin <manikulin@gmail.com>]

On 16/10/2022 04:35, Juan Manuel Macías wrote:
>
> To begin with, it is a particular solution
> applied in a general way. This can have unexpected consequences, as has
> happened in verse blocks.

In my opinion Org has to apply a general solution merely because a table 
may be result of evaluation of an org-babel code block. I may be wrong, 
but I suspect that some users do not care what is the intermediate 
format when they need a PDF file.

> And finally, I think that applying a general solution to this problem is
> something that should be done(IMHO) in LaTeX and not in Org,

Org has a bit more information concerning context of square brackets. 
They may be just text of a table cell or contents of an export snippet. 
In a LaTeX file they are just square brackets and there is no way to 
distinguish them.

I believe, it is a design flaw in LaTeX that the \\ command does not 
have a counterpart with no optional * and [] arguments. For humans \\ is 
enough, but it is fragile when LaTeX is used as an intermediate export 
format. A part of the problem is that all 3rd party packages should be 
adapted for the robust \\ sibling. Likely it may be solved by additional 
pass in the exporter code but it will significantly increase its 
complexity. I have no idea what is appropriate place to discuss such 
issue with LaTeX developers.

The following is irrelevant to the recent changes. I have tried

---- >8 ----
text
#+begin_verse

a b
c d

e f
g h
#+end_verse
---- 8< ----

With the fix Ihor committed today I have got

---- >8 ----
text
\begin{verse}
\vspace*{1em}
a b\\\empty
c d\\\empty
\vspace*{1em}
e f\\\empty
g h\\\empty
\end{verse}
---- 8< ----

My expectation was
---- >8 ----
\begin{verse}
a b\\\empty
c d

e f\\\empty
g h
\end{verse}
---- 8< ----

I am surprised that \vspace is added instead of empty line between 
stanzas. Is there a reason to override LaTeX defaults? If such reason 
exists would not it better to add

     \parskip=1em plus 0.5em minus 0.25em\relax

before first verse line? Is hard coded rigid vertical space acceptable 
when high quality output is desired? \vspace before first line looks 
like a bug. Frankly speaking, nested calls of `replace-regexp-in-string' 
makes the code hard to read.

P.S. I have not found exact citation, but I noticed a mention: Lamport 
expected that verse environment would get negative feedback from poets.