Using when with a command's exit status

[wgordon17]

Is it possible, especially with Tasks, to set when to be a command, and the task runs based on the exit status of the command? Where a status of 0 == true, i.e., if the when command succeeds then the task is skipped.

E.g.,

_tasks:
  - command: "git init"
    when: "! git log -1 --pretty=oneline || false"

In my example, git init will only run if a git repository doesn't already exist (git log -1 --pretty=oneline returns true for an existing repo and false, the exit code is inverted with ! such that when is true if git log -1 --pretty=oneline is false).

If this isn't already possible, perhaps it could be possible to implement something like when_command?

[sisp]

How about using, e.g., jinja2-shell-extension and calling your status command in a when template?

_jinja_extensions:
  - jinja2_shell_extension.ShellExtension

_tasks:
  - command: "git init"
    when: "{{ 'git log -1 --pretty=oneline && echo \"false\" || echo \"true\"' | shell }}"

(Disclaimer: I haven't tested this template, but this or something similar should work.)

Or you could register your own tiny Jinja2 extension that directly translates a shell exit code to "true"/"false". See, e.g., https://github.com/pawamoy/copier-uv/blob/main/extensions.py + https://github.com/pawamoy/copier-uv/blob/main/copier.yml#L11-L14.

[wgordon17]

Ohh, that's nifty! Let me give that a try (wow, what won't they make a Jinja extension for?? 😅)

[wgordon17]

For anyone else coming across this, I technically didn't try the jinja2-shell-extension extension (or the similar jinja2-shell either) because neither were available as Nix packages. But, I was able to get this working with jinja2-git.

_jinja_extensions:
    - jinja2_git.GitExtension
_tasks:
  - command: "git init"
    when: "{% if gitcommit %}false{% else %}true{% endif %}"

Edit: Ok, so this turns out to not work the way I expected. Once I actually started testing this for real, it was just throwing errors or silenting giving the wrong output.

[wgordon17]

Alrighty, so after not finding exactly what I was looking for, I went off and built it (because...why not ¯\_(ツ)_/¯ ).

The Jinja extension is available here: https://github.com/gordon-code/jinja2-git-dir?tab=readme-ov-file#copier
and even includes a section to how to use/apply within Copier. Hope this helps anyone else who might stumble across it!

_jinja_extensions:
    - jinja2_git_dir.GitDirectoryExtension
_tasks:
  - command: "git init"
    when: "{{ _copier_conf.dst_path | realpath | gitdir is false }}"
  - command: "git commit -am 'initial commit'"
    when: "{{ _copier_conf.dst_path | realpath | emptygit is true }}"
  - command: "git commit -am 'template update applied'"
    when: "{{ _copier_conf.dst_path | realpath | emptygit is false }}"