nextflow.script

The nextflow.script package implements the parsing and execution of Nextflow scripts.

Class Diagram

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Some classes may be excluded from the above diagram for brevity.

Notes

The execution of a Nextflow pipeline occurs in two phases. In the first phase, Nextflow parses and runs the script (using the language extensions in nextflow.ast and nextflow.extension), which produces the workflow DAG. In the second phase, Nextflow executes the workflow.

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In DSL1, there was no separation between workflow construction and execution -- dataflow operators were executed as soon as they were constructed. DSL2 introduced lazy execution in order to separate process definition from execution, and thereby facilitate subworkflows and modules.