Implicit variable launchDir breaks caching

[Sodbo]

Bug report

Ciao from Human Technopole, Milano!

Expected behavior and actual behavior

Using the $launchDir variable in the script: section breaks caching (the process gets executed even though nothing has changed).

Steps to reproduce the problem

#!/usr/bin/env nextflow

nextflow.enable.dsl = 2

process test_cache_launchDir {
    output:
        path("result.txt"), emit: result
    
    script:
    """
    file ${launchDir}/foo.txt > result.txt
    """
}

process test_cache_projectDir {
    output:
        path("result.txt"), emit: result
    
    script:
    """
    file ${projectDir}/foo.txt > result.txt
    """
}

workflow {
    test_cache_launchDir()
    test_cache_projectDir()
}

Program output

[bugtest]sodbo.sharapov@hnode02$ nextflow run main.nf

Nextflow 24.04.4 is available - Please consider updating your version to it

 N E X T F L O W   ~  version 24.04.2

Launching `main.nf` [pedantic_bose] DSL2 - revision: a61cfacf8f

executor >  local (2)
[8f/62d857] process > test_cache_launchDir  [100%] 1 of 1 ✔
[d3/32cc2a] process > test_cache_projectDir [100%] 1 of 1 ✔

[bugtest]sodbo.sharapov@hnode02$ nextflow run main.nf -resume

Nextflow 24.04.4 is available - Please consider updating your version to it

 N E X T F L O W   ~  version 24.04.2

Launching `main.nf` [sleepy_kalman] DSL2 - revision: a61cfacf8f

executor >  local (1)
[39/6cbe9d] process > test_cache_launchDir  [100%] 1 of 1 ✔
[d3/32cc2a] process > test_cache_projectDir [100%] 1 of 1, cached: 1 ✔

Environment

• Nextflow version: 24.04.2
• Java version: openjdk/17.0.8.1_1
• Operating system: linux
• Bash version: GNU bash, version 4.4.19(1)

Additional context

A similar problem with projectDir was fixed three years ago in Issue #2186. The fix was implemented in commit 7a4d1f1.

I also checked the task hashes, and they differ between same runs, as it was reported here.