Bug: snakefmt erroneously removes double braces, {{x}} -> {x}

[corneliusroemer]

Snakefmt makes illegal syntax changes:

rule align:
    input:
        sequences="results/{build_name}/filtered.fasta",
    params:
        translation_template=lambda w: f"results/{w.build_name}/translations/{{cds}}.fasta",

is formatted to

rule align:
    input:
        sequences="results/{build_name}/filtered.fasta",
    params:
        translation_template=lambda w: f"results/{w.build_name}/translations/{cds}.fasta",

I.e. the double curly braces around {{cds}} are replaced by single curly braces {cds}.

This might be ok to do in Python, but it isn't ok in Snakemake, as I need literal braces here, no replacement at all is wanted.

This happens with the snakefmt in precommit: rev: v0.8.4

[corneliusroemer]

I updated the version to 0.8.5 in precommit but I still get the error. Weirdly, when I run snakefmt. --check from command line with version 0.8.5 I don't get any error.

[mbhall88]

Ooof that's not good. Sorry it's been hard to find time to work on this tool in recent months.
I will try and look into these bugs in the coming month or two, but feel free to have a look too. We'd be very happy to have the community involved

[corneliusroemer]

No worries at all, I understand it's hard to maintain snakefmt.

This bug is really weird, the fact it's only affecting pre-commit could mean something is wrong in that part, or maybe not even within snakefmt. I'll see if I can investigate further, this seems hard to repro for others, I think.

[mbhall88]

@corneliusroemer I can't replicate this error in snakefmt 0.8.5. Can you confirm your precommit is definitely using 0.8.5?

[corneliusroemer]

I'm trying to set up a minimal reproducible example but getting some weird pre-commit installed errors like:

 note: This error originates from a subprocess, and is likely not a problem with pip.
      ERROR: Failed building wheel for multidict
    ERROR: Could not build wheels for multidict, which is required to install pyproject.toml-based projects

Will have a look later and try again when I have more time.

[y9c]

Might relative to Python version? Can reproduce under Python 3.12

[corneliusroemer]

Great catch @y9c!