Use usage variables in inputs/outputs

[cdevienne]

I have a task that produces a different output depending on the arg I pass to it. The idea is to use this task as a dependency of others to share some common rules.
A big limitation I have is that I cannot use "{{usage.myarg}}" in the inputs and outputs attributes.

Dummy example of such a task:

[tasks.touch]
usage = 'arg "<filename>"'
outputs = ["{{usage.filename}}"]
run = "touch {{usage.filename}}"

If I run mise, I get a "Variable usage is not defined".

Am I right thinking we should be able to do that? Or am I doing an anti-pattern, and a better way exists?

[jdx]

Yes, this makes sense. The failure happens because sources and outputs are currently rendered before the task invocation’s usage arguments are available.

I opened #13051 to defer usage-dependent source/output templates until those arguments have been parsed, including for tasks invoked as dependencies. The resolved paths then participate normally in freshness and task-cache behavior.

AI-assisted — Tool: Codex; model: openai/gpt-5; version: unavailable.