Beyond started with the Guix workflow language

Recap

In the previous section we defined a workflow. This section builds on the knowledge from the previous section, so if you haven't read that, now is the time to get beyond started.

Extending workflows

In the dynamic-workflow we created files and compressed them. In the following workflow we will generate a file containing some information about these compressed files to learn how we can extend a workflow at any point in a new workflow.

;; We are going to extend the workflow defined in the file
;; "example-workflow.w".
define dynamic-workflow
  load-workflow "example-workflow.w"

process: (list-file-template filename)
  name
    string-append "list-file-"
                  basename filename
  packages "gzip"
  inputs filename
  outputs
    string-append filename ".list"
  run-time
    complexity
      space 20 mebibytes
      time  30 seconds
  # { gzip --list {{inputs}} > {{outputs}} }


;; Get all processes of the other workflow.
define foreign-processes
  workflow-processes dynamic-workflow

;; Get the processes that we want to extend on.
define compress-file-processes
  processes-filter-by-name foreign-processes "compress-file"

;; Create the new processes.
define list-file-processes
  map list-file-template
      append-map process-outputs compress-file-processes

workflow: extended-dynamic-workflow
  processes
    append
      ;; These are the process connections of the imported workflow
      workflow-restrictions dynamic-workflow
      ;; And these are the new process connections.  The "zip" procedure
      ;; pairs up each of the processes in "list-file-processes" with
      ;; one of the processes in "compress-file-processes".
      zip list-file-processes compress-file-processes

With list-file-template we created a procedure that returns a process that generates a file containing details about the compressed archive. We use this function in extended-dynamic-workflow to run after each compress-file process.

In the processes field we include the contents of dynamic-workflow, thereby concisely extending it.

Further reading

The GNU Guile and GNU Guix manuals are good places to learn the language and concepts on which GWL builds.