[bug] conan upload --list errors on empty recipe list

[n-morales]

Environment details

• Operating System+version:
  Manjaro Linux 23.0.0

• Compiler+version:
  N/A

• Conan version:
  Conan version 2.0.7

• Python version:
  Python 3.11.3

Steps to reproduce

1. Create a list file as follows (can be generated from something like conan list --graph install_graph.json --graph-binaries build --format json)

{
  "Local Cache": {}
}

2. conan upload --remote foo --list list.json
3. Conditional check fails: https://github.com/conan-io/conan/blob/release/2.0/conan/cli/commands/upload.py#L84-L85

Note that I believe this should work since some automation workflows in CI may result in an empty list if a specific package was just cached and --graph-binaries build is set in the list command. I think the conditional check listed below should probably only error if the --list argument was not provided.

Logs

$> conan upload --remote foo --list list.json
ERROR: No recipes found matching pattern 'None'

[AbrilRBS]

Hi @n-morales, thanks a lot for your report and taking the time to diagnose the error!

What you describe seems like a valid use case to me, if you would like to contribute a PR now that you have checked the code, we can discuss it there, but no worries if not :)
(I can't promise it would get merged if the team thinks otherwise of the error, but the discussion is at least worth having, so thanks for bringing it up!)

[memsharded]

I think that for automation purposes, allowing an empty list makes sense. So this could be changed, and relaxed for the --list argument. It sounds that an info/warning message would be useful, I'd add it too.

So @n-morales would you like to contribute it as you as @RubenRBS suggested? Otherwise, please tell us and we will do it, no problem at all. Thanks!

[n-morales]

@RubenRBS @memsharded I could do it -- do you have suggestions for where I should be putting a unit test for it?

[memsharded]

Probably https://github.com/conan-io/conan/blob/release/2.0/conans/test/integration/command_v2/test_combined_pkglist_flows.py#L9 is the best, as it contains other upload --list tests. But no need to reuse the fixture with previous data,