dynamic filepaths not publishing when using new publish feature on 25.01.0-edge

[katgorski]

Bug report

Expected behavior and actual behavior

Using the new publish feature, the following pipeline publishes a file with the correct dynamic filepath in Nextflow 24.04.4, but on Nextflow 25.01.0-edge causes the error Output `path` directive should return a string or closure, but instead returned a org.codehaus.groovy.runtime.GStringImpl.

Steps to reproduce the problem

script:

nextflow.preview.output = true

process SALMON {

    container 'quay.io/biocontainers/salmon:1.10.3--haf24da9_3'
    tag "${name}"
    
    input:
    path index
    tuple val(name), path(r1), path(r2)

    output:
    tuple val(name), path(quant)

    script:
    """
    salmon quant -i $index -l A -1 $r1 -2 $r2 -o quant
    """
}

workflow {
    index = channel.value('/path/to/index')
    raw_data = channel.of(['test', '/path/to/test_1.fq.gz', '/path/to/test_2.fq.gz'])
    SALMON(index, raw_data)

    publish:
    SALMON.out >> 'samples'
}

output {
    samples {
        path { s -> "phase2/${s[0]}/salmon" }
        // publishes correctly in 25.01.0-edge if the line is
        // path { s -> "phase2/${s[0]}/salmon".toString() }
    }
}

Program output

 N E X T F L O W   ~  version 25.01.0-edge

Launching `reproducible-example.nf` [high_tuckerman] DSL2 - revision: b27fc685ee

WARN: WORKFLOW OUTPUT DSL IS A PREVIEW FEATURE - SYNTAX AND FUNCTIONALITY CAN CHANGE IN FUTURE RELEASES
executor >  local (1)
[3b/cb75ae] process > SALMON (test) [100%] 1 of 1 ✔
Output `path` directive should return a string or closure, but instead returned a org.codehaus.groovy.runtime.GStringImpl

v24.10.4.nextflow.log
v25.01.0-edge.nextflow.log

Environment

• Nextflow version: 24.10.4/25.01.0-edge
• Java version: openjdk 17.0.10 2024-01-16 LTS
• Operating system: macOS 15.3.1
• Bash version: zsh 5.9 (arm64-apple-darwin24.0)

Additional context

Slack thread here

[bentsherman]

Thanks for reporting. Always annoying these dynamic strings. I will draft a fix for next edge release