output block is needed for publishing outputs from workflow

[fgroll]

Bug report

When using the second preview version for publishing outputs from workflows the output block is required for files to be actually published. Nothing needs to be set within the block, output {} is enough for files to be published. Omitting this line prevents any file from being published.

Expected behavior and actual behavior

The documentation for Customizing outputs clearly states that the output block is only needed for customizing the output and can be omitted when the default behaviour is good enough. But that doesn't seem to be the case, as omitting the output block prevents any file from being published.

Steps to reproduce the problem

workflow.nf

#!/usr/bin/env nextflow

nextflow.preview.output = true

process doStuff {
    output:
        path 'file.txt'

    script:
        """
        touch file.txt
        """
}


workflow {
    main:
        println "outputDir: $workflow.outputDir"
        out = doStuff()
        out.view { file -> "Out: ${file}" }

    publish:
        out >> "default"
    
}

// Uncomment the next line to actually publish the output file
// output {}

Run this file once and check with ls to see no results directory

NXF_VER=24.10.0 nextflow run workflow.nf
ls -lh

And then run it again after uncommenting the last line to see the results directory

NXF_VER=24.10.0 nextflow run workflow.nf
ls -lh

Program output

N E X T F L O W  ~  version 24.10.0
Launching `workflow.nf` [hopeful_sanger] DSL2 - revision: d4837e8320
WARN: WORKFLOW OUTPUT DSL IS A PREVIEW FEATURE - SYNTAX AND FUNCTIONALITY CAN CHANGE IN FUTURE RELEASES
outputDir: /absolute/path/to/current/directory/results
[be/c36072] Submitted process > doStuff
Out: /absolute/path/to/current/directory/work/be/c360721f8d99f992ba55284f903b45/file.txt

.nextflow.log

Environment

• Nextflow version: 24.10.0
• Java version: openjdk 11.0.13 2021-10-19
• Operating system: Rocky Linux 8.10 (Green Obsidian)
• Bash version: GNU bash, version 4.4.20(1)-release

[bentsherman]

Good catch, and sorry for the confusion. I will fix it (this time with a test case 😅 ) and try to get it into the next patch release