Set accelerator through CLI only if set explicitly

[awaelchli]

What does this PR do?

Fixes the following use case:

import lightning as L


if __name__ == "__main__":
    fabric = L.Fabric(accelerator="mps")
    print(fabric.device)

lightning run model train.py

We can make a special exception for precision as well. For the rest of the arguments, devices and num_nodes, we need to remain strict and won't allow the user to have a different setting in the code vs. CLI.

cc @Borda @carmocca @justusschock @awaelchli

[github-actions]

⚡ Required checks status: All passing 🟢

Groups summary

🟢 pytorch_lightning: Tests workflow

Check ID	Status
pl-cpu (macOS-11, lightning, 3.8, 1.11)	success	✅
pl-cpu (macOS-11, lightning, 3.9, 1.12)	success	✅
pl-cpu (macOS-11, lightning, 3.10, 1.13)	success	✅
pl-cpu (macOS-11, lightning, 3.8, 1.11, oldest)	success	✅
pl-cpu (ubuntu-20.04, lightning, 3.9, 1.11)	success	✅
pl-cpu (ubuntu-20.04, lightning, 3.10, 1.12)	success	✅
pl-cpu (ubuntu-20.04, lightning, 3.10, 1.13)	success	✅
pl-cpu (ubuntu-20.04, lightning, 3.8, 1.11, oldest)	success	✅
pl-cpu (windows-2022, lightning, 3.9, 1.11)	success	✅
pl-cpu (windows-2022, lightning, 3.10, 1.12)	success	✅
pl-cpu (windows-2022, lightning, 3.10, 1.13)	success	✅
pl-cpu (windows-2022, lightning, 3.8, 1.11, oldest)	success	✅
pl-cpu (macOS-11, pytorch, 3.8, 1.13)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.8, 1.13)	success	✅
pl-cpu (windows-2022, pytorch, 3.8, 1.13)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 pytorch_lightning: Azure GPU

Check ID	Status
pytorch-lightning (GPUs)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 pytorch_lightning: Azure HPU

Check ID	Status
pytorch-lightning (HPUs)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 pytorch_lightning: Azure IPU

Check ID	Status
pytorch-lightning (IPUs)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 lightning_fabric: CPU workflow

Check ID	Status
fabric-cpu (macOS-11, lightning, 3.8, 1.11)	success	✅
fabric-cpu (macOS-11, lightning, 3.9, 1.12)	success	✅
fabric-cpu (macOS-11, lightning, 3.10, 1.13)	success	✅
fabric-cpu (macOS-11, lightning, 3.8, 1.11, oldest)	success	✅
fabric-cpu (ubuntu-20.04, lightning, 3.9, 1.11)	success	✅
fabric-cpu (ubuntu-20.04, lightning, 3.10, 1.12)	success	✅
fabric-cpu (ubuntu-20.04, lightning, 3.10, 1.13)	success	✅
fabric-cpu (ubuntu-20.04, lightning, 3.8, 1.11, oldest)	success	✅
fabric-cpu (windows-2022, lightning, 3.9, 1.11)	success	✅
fabric-cpu (windows-2022, lightning, 3.10, 1.12)	success	✅
fabric-cpu (windows-2022, lightning, 3.10, 1.13)	success	✅
fabric-cpu (windows-2022, lightning, 3.8, 1.11, oldest)	success	✅
fabric-cpu (macOS-11, fabric, 3.8, 1.13)	success	✅
fabric-cpu (ubuntu-20.04, fabric, 3.8, 1.13)	success	✅
fabric-cpu (windows-2022, fabric, 3.8, 1.13)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py, tests/tests_fabric/test_cli.py, tests/tests_fabric/test_connector.py.

🟢 lightning_fabric: Azure GPU

Check ID	Status
lightning-fabric (GPUs)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py, tests/tests_fabric/test_cli.py, tests/tests_fabric/test_connector.py.

🟢 mypy

Check ID	Status
mypy	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 install

Check ID	Status
install-pkg (ubuntu-22.04, app, 3.8)	success	✅
install-pkg (ubuntu-22.04, app, 3.10)	success	✅
install-pkg (ubuntu-22.04, fabric, 3.8)	success	✅
install-pkg (ubuntu-22.04, fabric, 3.10)	success	✅
install-pkg (ubuntu-22.04, pytorch, 3.8)	success	✅
install-pkg (ubuntu-22.04, pytorch, 3.10)	success	✅
install-pkg (ubuntu-22.04, lightning, 3.8)	success	✅
install-pkg (ubuntu-22.04, lightning, 3.10)	success	✅
install-pkg (ubuntu-22.04, notset, 3.8)	success	✅
install-pkg (ubuntu-22.04, notset, 3.10)	success	✅
install-pkg (macOS-12, app, 3.8)	success	✅
install-pkg (macOS-12, app, 3.10)	success	✅
install-pkg (macOS-12, fabric, 3.8)	success	✅
install-pkg (macOS-12, fabric, 3.10)	success	✅
install-pkg (macOS-12, pytorch, 3.8)	success	✅
install-pkg (macOS-12, pytorch, 3.10)	success	✅
install-pkg (macOS-12, lightning, 3.8)	success	✅
install-pkg (macOS-12, lightning, 3.10)	success	✅
install-pkg (macOS-12, notset, 3.8)	success	✅
install-pkg (macOS-12, notset, 3.10)	success	✅
install-pkg (windows-2022, app, 3.8)	success	✅
install-pkg (windows-2022, app, 3.10)	success	✅
install-pkg (windows-2022, fabric, 3.8)	success	✅
install-pkg (windows-2022, fabric, 3.10)	success	✅
install-pkg (windows-2022, pytorch, 3.8)	success	✅
install-pkg (windows-2022, pytorch, 3.10)	success	✅
install-pkg (windows-2022, lightning, 3.8)	success	✅
install-pkg (windows-2022, lightning, 3.10)	success	✅
install-pkg (windows-2022, notset, 3.8)	success	✅
install-pkg (windows-2022, notset, 3.10)	success	✅

These checks are required after the changes to src/lightning/fabric/cli.py.

🟢 link-check

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markdown-link-check	success	✅

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---

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[codecov]

Codecov Report

Merging #16818 (aa42b9f) into master (83b8899) will decrease coverage by 21%.
The diff coverage is 100%.

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #16818     +/-   ##
=========================================
- Coverage      81%      59%    -21%     
=========================================
  Files         416      411      -5     
  Lines       31736    31271    -465     
=========================================
- Hits        25559    18512   -7047     
- Misses       6177    12759   +6582