I'm writing a subworkflow which has two processes. When testing it, I find that only the first input is processed. The input:

input[1] = channel.fromList([
    [
        [id:'test3'],
        file(params.modules_testdata_base_path + 'genomics/sarscov2/illumina/bam/test.paired_end.sorted.bam', checkIfExists: true),
        file(params.modules_testdata_base_path + 'genomics/sarscov2/illumina/bam/test.paired_end.sorted.bam.bai', checkIfExists: true),
    ],
    [
        [id:'test4'],
        file(params.modules_testdata_base_path + 'genomics/sarscov2/nanopore/bam/sars-cov-2_v5.3.2.bam', checkIfExists: true),
        file(params.modules_testdata_base_path + 'genomics/sarscov2/nanopore/bam/sars-cov-2_v5.3.2.bam.bai', checkIfExists: true),
    ],
])
input[2] = channel.of([1,2])
input[3] = 20
"""

Using

view

I can see the input channel is accepting both test3 and test4 but only test3 is processed. Also checked the output which should be combined into one tsv file, it only contains test3 results. Any idea why this would happen?

input[2]

is only one value ( a list of two elements ). So it only get's paired up with the first element of

input[1]

.

input[2]

should either be a value channel (

input[2] = channel.value([1,2])

) or you need to give it two values ( I'm not sure if you also intended that to be channel.fromList or the square brackets are just extra )

That was it! Thanks Mahesh ❤️

Because it's a plain value. So it gets turned into a value channel implicitly. It's not documented (that I can see) but I think that

channel.of

always returns a queue channel even when it's only a single value

Right, so to be explicit I should

channel.value(20)

?

yes, exactly