Fix AttributeError: 'NoneType' object has no attribute 'finalize' on TPU

[chizuchizu]

Fix AttributeError: 'NoneType' object has no attribute 'finalize'

What does this PR do?

Issue

import pytorch_lightning as pl

my_model = MyLightningModule()
trainer = pl.Trainer(tpu_cores=8, logger=None)
trainer.fit(my_model)

If you run the code written above, you will get the error below.

/opt/conda/lib/python3.7/site-packages/pytorch_lightning/plugins/training_type/tpu_spawn.py in _close_logger(self, trainer)
    236     def _close_logger(self, trainer) -> None:
    237         if hasattr(trainer, "logger"):
--> 238             trainer.logger.finalize("success")
    239 
    240     @property

AttributeError: 'NoneType' object has no attribute 'finalize'

This bug is caused by not being able to handle the case where the attribute logger exists and logger.finalize does not.

CHANGE

pytorch_lightning/plugins/training_type/tpu_spawn.py the 249th line

BEFORE

def _close_logger(self, trainer) -> None:
    if hasattr(trainer, "logger"):
        trainer.logger.finalize("success")

AFTER

def _close_logger(self, trainer) -> None:
    if hasattr(trainer, "logger.finalize"):
        trainer.logger.finalize("success")

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
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• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

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Did you have fun?

This is the first pull request to OSS in my life. So, of course, yes:)

[codecov]

Codecov Report

Merging #6221 (8af16be) into master (ff16104) will decrease coverage by 3%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #6221    +/-   ##
=======================================
- Coverage      94%     90%    -3%     
=======================================
  Files         161     161            
  Lines       11486   11376   -110     
=======================================
- Hits        10745   10275   -470     
- Misses        741    1101   +360     

[Borda]

mind add chlog :]
also pls keep the bullet-list form template

[chizuchizu]

@Borda

Thanks for the review.

I've added bulle-list and CHANGELOG.md.

[tchaton]

Thanks for resolving my bug :)