[lilypond.lua]: non-trivial ly code doesn't compile; global options not effective

[ppenguin]

I just discovered lilypond.lua and it might be what I was looking for.

However, I had some trouble getting it to work.

The following works well:

---
lilypond:
  relativize: yes
---

# Some songs

```lilypond { .ly-fragment ly-resolution=300 }
\new ChordNames \with {
  \override BarLine.bar-extent = #'(-1 . 3)
  \consists "Bar_engraver"
}

\chordmode {
  f1:maj7 f:7 bes:7
  c:m d:7 fis:dim
}

However, as soon as I add the lilypond block from here (examples), I get an error:

$ pandoc -i test/lp1.md --lua-filter=$(which lilypond.lua) --pdf-engine=lualatex --standalone -o test/lp1.pdf
Error running filter /nix/store/87wba0bq2w9icj63vd7m2ipl2fn1a866-pandoc-lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:
...lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:65: attempt to index a nil value (local 'fh')
stack traceback:
	...lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:49: in upvalue 'generate_image'
	...lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:83: in upvalue 'process_lilypond'
	...lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:143: in function <...lua-filters-2021-11-05/share/pandoc/filters/lilypond.lua:138>

The same happens when I add a \break to any of the above code.

As I gleaned from the lua code, this probably means that the lilypond process errored out and dind't produce an image file. But if I put the verbatim contents of the failing code block in a separate file lptst.ly and then manually run lilypond, it generates a correct looking png file:

$ lilypond -o tst.png --png test/lptst.ly
GNU LilyPond 2.24.3 (running Guile 2.2)
Processing `test/lptst.ly'
Parsing...
test/lptst.ly:1: warning: no \version statement found, please add

\version "2.24.3"

for future compatibility
Interpreting music...[8][16]
Preprocessing graphical objects...
Finding the ideal number of pages...
Fitting music on 1 page...
Drawing systems...
Converting to PNG...
Success: compilation successfully completed

The second topic:

I want to move things like ly-resolution=300 to the frontmatter (which should be possible according to the docs), but none of

---
lilypond:
  relativize: yes
  ly-resolution: 300
ly-resolution: 300
pandoc:
  ly-resolution: 300
---

had any effect.

[ppenguin]

Partial Solution

I discovered that if I omit .ly-fragment, I'm able to do \break and the orginal appoggiaturas example also works (which has in the original test markdown also .ly-fragment however, so why would it pass the test there?).

Ultimately this could mean, that it would be good to be able to tweak the ly-fragment behaviour, or provide another mechanism that allows us a kind of default preamble that will be injected for each block, so we can avoid repeated setup boilerplate.