Saturday, November 23, 2024

Re: Syntax: allow newline but not blank lines in a region



Den lör 23 nov. 2024 04:59Doug Kearns <dougkearns@gmail.com> skrev:
On Sat, 23 Nov 2024 at 04:28, BPJ <bpj@melroch.se> wrote:
I have a syntax for a markup language where certain delimited constructs allow single newlines but not blank lines, i.e. this is OK

``` markup
{_foo
bar_}
```

but this is not OK

``` markup
{_foo

bar_}
```

is there any way to set up a region so that it behaves like this? I tried `oneline` plus a contained `syn match` which matches a newline not preceded or followed by a blank line but no luck!

I get the behavior I want with a `syn match` with this pattern

``` pattern
{_\%([^\n]\|\%(\_^\s*\)\@<!\n\%(\s*\_$\)\@!\)\{-}_}
```

Does something like this work?

:syn region foobar start="{_" end="_}" end="$" skip="\n\s*\S"


I already tried that. No lunch unfortunately. I'm going with the `syn match` version which incorporates the single newline pattern. It is probably less efficient but is also probably my only choice now as I found that I also need to exclude backslash from the "normal" subpattern and skip past backslash + char lest the closing delimiter is directly preceded by a backslash.

BTW for reference the correct pattern, maybe inefficient but accurate, for a newline not preceded or followed by any blank line is

``````pattern
\%(\_^\s*\)\@<!\n\%(\s*\_$\)@!
``````

i.e. with negative lookbehind for optional horizontal whitespace and a start-of-line and the opposite negative lookahead for optional horizontal whitespace and an end-of-line.

FWIW the backslash escape pattern I used is `\\\_.`, with later Special highlighting of backslashes followed by ASCII punctuation or space/newline/return. Who said it has to be easy! :-)

 
but then highlighting obviosly doesn't kick in until I type the closing delimiter so I would prefer a region.

Also is there a better way to match the start or end of the file than `\_.\@<!` and `\_.\@!`?

:help \%^

Thanks. I still learn new things about Vim after having used it for ~20 years, which is both gratifying and frustrating!

/bpj



Regards,
Doug

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