Optional username/channel treated differently on different OSes

[Artalus]

We attempt to use Github Actions + CPT in Conan-Center-Index fork. Most of recipes there use new convention with optional username and channel for packages, and it seems CPT is not quite ready for this:

• if we specify CONAN_REFERENCE as simply lib/ver, CPT on Linux fails with this:

  Traceback (most recent call last):
  File "/home/iivanov/git/conan-center-index/build.py", line 6, in <module>
  builder = ConanMultiPackager()
  File "/home/iivanov/.local/lib/python3.8/site-packages/cpt/packager.py", line 211, in __init__
  self.reference = ConanFileReference(name, version, self.username, self.channel)
  File "/home/iivanov/.local/lib/python3.8/site-packages/conans/model/ref.py", line 164, in __new__
  raise InvalidNameException("Specify the 'user' and the 'channel' or neither of them")
  conans.errors.InvalidNameException: Specify the 'user' and the 'channel' or neither of them

  This seems to happen due to channel being set to testing automatically in CPT innards.

• if we change it to lib/ver@/, CPT works fine on Linux, but will fail on Mac

  Traceback (most recent call last):
  File "../../../build.py", line 8, in <module>
  builder.run()
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/cpt/packager.py", line 541, in run
  self.run_builds(base_profile_name=base_profile_name)
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/cpt/packager.py", line 633, in run_builds
  r.run()
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/cpt/runner.py", line 121, in run
  self._results = self._conan_api.create(self._conanfile, name=name, version=version,
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/conans/client/conan_api.py", line 81, in wrapper
  return f(api, *args, **kwargs)
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/conans/client/conan_api.py", line 341, in create
  new_ref = cmd_export(self.app, conanfile_path, name, version, user, channel, keep_source,
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/conans/client/cmd/export.py", line 80, in cmd_export
  ref = ConanFileReference(conanfile.name, conanfile.version, user, channel)
  File "/Users/runner/hostedtoolcache/Python/3.8.1/x64/lib/python3.8/site-packages/conans/model/ref.py", line 164, in __new__
  raise InvalidNameException("Specify the 'user' and the 'channel' or neither of them")
  conans.errors.InvalidNameException: Specify the 'user' and the 'channel' or neither of them

• if, however, we specify envvars CONAN_USERNAME=_ and CONAN_CHANNEL=_, then Linux fails, yet Mac works

  Traceback (most recent call last):
  File "/opt/pyenv/versions/3.6.7/bin/run_create_in_docker", line 11, in <module>
  load_entry_point('conan-package-tools==0.31.1', 'console_scripts', 'run_create_in_docker')()
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/cpt/run_in_docker.py", line 53, in run
  runner.run()
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/cpt/runner.py", line 127, in run
  update=self._update_dependencies)
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/conans/client/conan_api.py", line 81, in wrapper
  return f(api, *args, **kwargs)
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/conans/client/conan_api.py", line 343, in create
  ignore_dirty=ignore_dirty)
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/conans/client/cmd/export.py", line 80, in cmd_export
  ref = ConanFileReference(conanfile.name, conanfile.version, user, channel)
  File "/opt/pyenv/versions/3.6.7/lib/python3.6/site-packages/conans/model/ref.py", line 164, in __new__
  raise InvalidNameException("Specify the 'user' and the 'channel' or neither of them")
  conans.errors.InvalidNameException: Specify the 'user' and the 'channel' or neither of them
  Traceback (most recent call last):
  File "/home/iivanov/git/conan-center-index/build.py", line 8, in <module>
  builder.run()
  File "/home/iivanov/.local/lib/python3.8/site-packages/cpt/packager.py", line 547, in run
  self.run_builds(base_profile_name=base_profile_name)
  File "/home/iivanov/.local/lib/python3.8/site-packages/cpt/packager.py", line 673, in run_builds
  r.run(pull_image=not pulled_docker_images[docker_image],
  File "/home/iivanov/.local/lib/python3.8/site-packages/cpt/runner.py", line 304, in run
  raise Exception("Error building: %s" % command)

The current working solution for us is to specify CONAN_REFERENCE for Linux builds and CONAN_CHANNEL+_USERNAME for Mac builds, but this is rather cumbersome.

Environment Details

• Conan Package Tools Version: 0.31.1
• Operating System: Linux / Mac
• Conan version: conan 1.22.2

[Artalus]

On a side note, it also seems that when no CONAN_STABLE_CHANNEL is provided, CPT will substitute it for stable. I am unsure if this needs any correction, since omitting username and channel have not yet become a widespread practice.

[Artalus]

Also, with CONAN_STABLE_BRANCH_PATTERN=... + CONAN_STABLE_CHANNEL=_ one will also get an error saying

 >> Branch detected
   >> trassir-ci
 >> Info
   >> Redefined channel by CI branch matching with 'trassir-ci', setting CONAN_CHANNEL to '_'
Traceback (most recent call last):
...
conans.errors.InvalidNameException: Specify the 'user' and the 'channel' or neither of them

[Artalus]

So I did some more digging and turns out the problem is not Linux-specific, but Docker-specific. The issue was CONAN_USERNAME being discarded instead of forwarding to Docker. I made a PR fixing this.

[uilianries]

Fixed by #522

Should be available on CPT 0.35.1