Feature flags

Feature flags are used to introduce experimental or other opt-in features. They can be specified in the pipeline script or the configuration file.

nextflow.enable.configProcessNamesValidation

When true, prints a warning for every withName: process selector that doesn’t match a process in the pipeline (default: true).

nextflow.enable.dsl

Defines the DSL version to use (1 or 2).

Changed in version 22.03.0-edge: DSL2 was made the default DSL version.

Changed in version 22.12.0-edge: DSL1 was removed.

nextflow.enable.moduleBinaries

When true, enables the use of modules with binary scripts. See Module binaries for more information.

nextflow.enable.strict

New in version 22.05.0-edge.

When true, the pipeline is executed in “strict” mode, which introduces the following rules:

  • When reading a params file, Nextflow will fail if a dynamic param value references an undefined variable

  • When merging params from a config file with params from the command line, Nextflow will fail if a param is specified from both sources but with different types

  • When using the join operator, the failOnDuplicate option is true regardless of any user setting

  • When using the join operator, the failOnMismatch option is true (unless remainder is also true) regardless of any user setting

  • When using the publishDir process directive, the failOnError option is true regardless of any user setting

  • In a process definition, Nextflow will fail if an input or output tuple has only one element

  • In a process definition, Nextflow will fail if an output emit name is not a valid identifier (i.e. it should match the pattern /[A-Za-z_][A-Za-z0-9_]*/)

  • During a process execution, Nextflow will fail if a received input tuple does not have the same number of elements as was declared

  • During a process execution, Nextflow will fail if the storeDir directive is used with non-file outputs

  • Nextflow will fail if a pipeline param is referenced before it is defined

  • Nextflow will fail if multiple functions and/or processes with the same name are defined in a module script

nextflow.preview.output

New in version 24.04.0.

Experimental: may change in a future release.

When true, enables the use of the workflow output definition.

nextflow.preview.recursion

New in version 21.11.0-edge.

Experimental: may change in a future release.

When true, enables process and workflow recursion.

nextflow.preview.topic

New in version 23.11.0-edge.

Changed in version 25.04.0: This feature flag is no longer required to use topic channels.

When true, enables topic channels feature.