Is there anything wrong with the container definition in the

happy-preppy

module? When I try to use it in my workflow (run with singularity), I get this error:

ERROR ~ Execution aborted due to an unexpected error

 -- Check script '/hps/software/users/goldman/ipoetzsch/nf_boss_experiments/modules/nf-core/happy/prepy/main.nf' at line: 7 or see '.nextflow.log' file for more details

And then in the log it states that

_java.lang.NullPointerException_: Cannot get property 'containerEngine' on null object

. This seems to be about the

workflow.containerEngine

object in the container definition of the module:

container "${ workflow.containerEngine in ['singularity', 'apptainer'] && !task.ext.singularity_pull_docker_container ?
        '<https://depot.galaxyproject.org/singularity/hap.py:0.3.15--py27hcb73b3d_0>':
        '<http://quay.io/biocontainers/hap.py:0.3.15--py27hcb73b3d_0|quay.io/biocontainers/hap.py:0.3.15--py27hcb73b3d_0>' }"

I have other nf-core modules with the exact same container directive (apart from the actual links) and those are not throwing this error. I checked and the two links point towards existing containers. Any idea what the problem could be?

Usually this is because one of your inputs is wrong

Ah that's very helpful. By wrong you mean incorrectly formatted?

Wrong shape, or something (a path) is empty that should not be

Thank you so much! I'll have a look.