Trainer property `log_dir` cannot be accessed before model is bound to trainer
🐛 Bug
Tentatives to access a Trainer instance's log_dir property prior to calling fit results in an error:
TypeError: expected str, bytes or os.PathLike object, not NoneType
Accessing log_dir only works after calling fit (or from within the training loop itself, once the setup required by fit has been executed).
To Reproduce
See bug reproduced with the BoringModel here.
Expected behavior
The Trainer's log_dir property should be accessible as soon as the Trainer is instantiated.
If this isn't possible because of some implementation detail, the documentation should at least be updated to clearly state this limitation.