Boolean flag default to `true` set to `false` through CLI is interpreted as a string

[VasLem]

Bug report

Currently there is no way to set a boolean flag defaulting to true to false naturally, unless you set it as typed.

Minimal example:

params.flag = true
process test {
script:
if (params.flag) {
    println "Flag is true"
} else {
    println "Flag is false"
}
"""
echo ${params.flag}
"""
}

workflow {
main:
test()
}

Run:

nextflow run test.nf --flag false

 N E X T F L O W   ~  version 26.02.0-edge

Launching `test.nf` [nauseous_visvesvaraya] revision: d3b98b5758

executor >  local (1)
[9d/b25e5a] test | 1 of 1 ✔
Flag is true

Expected behavior and actual behavior

I would expect to have the flag set to false, or at least have a way to do so, without using a typed param. This goes totally against the old CLI behavior.

Environment

• Nextflow version: 26.02.0-edge

[scwatts]

Here is another example where just setting a boolean parameter on the CLI results in the variable becoming a string:

params.boolean_flag = false

workflow {
  println "boolean_flag: ${params.boolean_flag} (${params.boolean_flag.getClass()})"
}

Run with default → boolean (expected)

$ NXF_VER=26.02.0-edge nextflow run ./main.nf

 N E X T F L O W   ~  version 26.02.0-edge

Launching `./main.nf` [spontaneous_yalow] revision: fa0d8aee84

boolean_flag: false (class java.lang.Boolean)

Run with boolean_flag set on CLI → string (unexpected)

$ NXF_VER=26.02.0-edge nextflow run ./main.nf --boolean_flag

 N E X T F L O W   ~  version 26.02.0-edge

Launching `./main.nf` [deadly_baekeland] revision: fa0d8aee84

boolean_flag: true (class java.lang.String)

This appears to be impacting a few nf-core pipelines:

• Using strict syntax causes template to raise an error when setting boolean options on CLI nf-core/tools#4100