validation metrics not logging properly

[jeremyjordan]

🐛 Bug

Validation metrics aren't being logged to the Trainer's logger.

To Reproduce

See Colab notebook: https://colab.research.google.com/drive/1O93pAD_cfSuVH6izyzrsn_xEe8v_2O7n?usp=sharing

Based on this test: https://github.com/PyTorchLightning/pytorch-lightning/blob/master/tests/trainer/test_eval_loop_logging_1_0.py

Code sample

from pytorch_lightning import Trainer
from tests.base.deterministic_model import DeterministicModel
import os
import torch
from pytorch_lightning.loggers import CSVLogger


class TestModel(DeterministicModel):
    def training_step(self, batch, batch_idx):
        acc = self.step(batch, batch_idx)
        acc = acc + batch_idx
        self.log('a', acc)
        self.log('b', acc, on_step=True, on_epoch=True)
        self.training_step_called = True
        return acc
    def validation_step(self, batch, batch_idx):
        acc = self.step(batch, batch_idx)
        acc = acc + batch_idx
        self.log('c', acc, on_step=False, on_epoch=True)
        self.log('d', acc, on_step=False, on_epoch=True)
        self.validation_step_called = True
        return acc
    def validation_step_end(self, acc):
        pass
    def validation_epoch_end(self, outputs):
        self.log('g', torch.tensor(2, device=self.device), on_epoch=True)
        self.validation_epoch_end_called = True
    def backward(self, trainer, loss, optimizer, optimizer_idx):
        loss.backward()


model = TestModel()
logger = CSVLogger("logs", name="my_exp_name")
trainer = Trainer(
    logger=logger,
    limit_train_batches=2,
    limit_val_batches=2,
    max_epochs=2,
    row_log_interval=1,
    weights_summary=None,
)
trainer.fit(model)

Expected behavior

Validation metric keys aren't present.

[jeremyjordan]

Fixed by #3763