Attribute finder doesn't check datamodule when hparams is set
🐛 Bug
Issue is seen here too: #3233 (comment)
See: https://github.com/rnett/pytorch-lightning/blob/6e5f232f5cec2b5e635ae34fa365c6b969d0902e/pytorch_lightning/utilities/parsing.py#L177
In pytorch_lightning.utilities.parsing.lightning_hasattr (and getattr and setattr), because hasattr(model, 'hparams') is used in the elif, checking only continues (i.e. to the dataloader) if hparams is not present.  It does not continue if hparams is present, but does not have the attribute.
I can make a PR, but the semantics needs to be decided on first, especially when hparams is a dict: do we only see the attribute if it is already present in the dict?  This is particularly important for making setting and getting match.