Cannot loop over task's generated files unless they already exist

[Leonid99]

Description

Trying to run the example from the docs https://taskfile.dev/docs/guide#looping-over-your-task-s-sources-or-generated-files (the one with for: generates). If no file exist (which is the common case -- this task is supposed to create this files), no "cat" happens. If both files already exist, it works as expected. If only one of the files exist, only that file is cat'ed.

❯ rm foo.txt
❯ rm bar.txt
❯ task
❯ touch bar.txt
❯ task
task: [default] cat bar.txt
❯ touch foo.txt
❯ task
task: [default] cat bar.txt
task: [default] cat foo.txt
❯

Version

3.45.5

Operating system

macOS

Experiments Enabled

No response

Example Taskfile

version: '3'

tasks:
  default:
    generates:
      - foo.txt
      - bar.txt
    cmds:
      - for: generates
        cmd: cat {{ .ITEM }}

[trulede]

@Leonid99 yes, your observation is correct, generates requires that the file exist when using with for, and its even worse than that (for what you want to do). Good news is you can redesign your taskfile slightly and get the outcome you want by using YAML anchors:

version: '3'

tasks:
  default:
    vars:
      FILES: &FILES
        - foo.txt
        - bar.txt
    generates: *FILES
    cmds:
      - for: { var: FILES }
        cmd: echo 'file={{ .ITEM }}'
      - for: generates
        cmd: echo 'generates={{ .ITEM }}'

[Leonid99]

@trulede Thank you, it does work, but are you saying that this behavior is intended? Why? This is very counter-intuitive, I would expect generates, pretty much by definition, to create the files (and treat missing files as changed, for the purposes of determination whether the task needs to run).

[trulede]

No, generates is what the task should produce if it runs correctly, and what needs to have been produced to indicate an up-to-date task. Its part of a dependency graph, similar to how a Makefile works. The task itself must create the files.

As for the implementation, I agree ... but its also not easy to change because generates also supports Globs, and that complicates matters. I've shown you how you can solve your problem.

Personally, I don't think its a useful feature (for with generates) because it does exactly nothing useful. But again, small change in approach, and its all good.