Process named output channels

[pditommaso]

The goal of this enhancement is to implement the ability to associate a custom name to each output channel declared in the process definition.

For example:

process foo {
  output:
    set val(sample_name), file('*_trimmed.fastq'), emit: named_fastq
    set val('trimmed'), file('*_trimmed.fastq'), emit: flagged_fastq
    file '*.log', emit: logs
  """
  command_here
  """
}

Using the above syntax the emit: option allows the association of a name that can be used to reference the channel output once the process has been invoked. For example:

workflow {
  foo()
  foo.out.named_fastq.view()
  foo.out.flagged_fastq.view()
}

This is similar to the request made by #1181, however, the use of as is discouraged because is a groovy lang keyword. Moreover the use of emit: is consistent with the new workflow output syntax definition #1276.

[mes5k]

This could be really nice!

I was thinking of a related feature, which is just the ability to destructure the output list, something like:

workflow {
  named_fastq, flagged_fastq = foo()
}

[pditommaso]

You can. foo.out implements a List therefore you can assign it as

workflow {
 foo()
 (named_fastq, flagged_fastq) = foo.out
}

[mes5k]

Oh perfect! I think I just had a bug in my test script that was leading me astray.

[pditommaso]

Use 19.08.1-edge for testing.