Fix: hparams.yaml saved twice when using TensorBoardLogger (#5953)

pytorch_lightning/loggers/tensorboard.py

@@ -224,14 +224,12 @@ def log_graph(self, model: LightningModule, input_array=None):
     def save(self) -> None:
         super().save()
         dir_path = self.log_dir
-        if not self._fs.isdir(dir_path):
-            dir_path = self.save_dir
 
         # prepare the file path
         hparams_file = os.path.join(dir_path, self.NAME_HPARAMS_FILE)
 
-        # save the metatags file if it doesn't exist
-        if not self._fs.isfile(hparams_file):
+        # save the metatags file if it doesn't exist and the log directory exists
+        if self._fs.isdir(dir_path) and not self._fs.isfile(hparams_file):
             save_hparams_to_yaml(hparams_file, self.hparams)
 
     @rank_zero_only

tests/loggers/test_tensorboard.py

@@ -291,3 +291,15 @@ def test_tensorboard_finalize(summary_writer, tmpdir):
     logger.finalize("any")
     summary_writer().flush.assert_called()
     summary_writer().close.assert_called()
+
+
+def test_tensorboard_save_hparams_to_yaml_once(tmpdir):
+    model = BoringModel()
+    logger = TensorBoardLogger(save_dir=tmpdir, default_hp_metric=False)
+    trainer = Trainer(max_steps=1, default_root_dir=tmpdir, logger=logger)
+    assert trainer.log_dir == trainer.logger.log_dir
+    trainer.fit(model)
+
+    hparams_file = "hparams.yaml"
+    assert os.path.isfile(os.path.join(trainer.log_dir, hparams_file))
+    assert not os.path.isfile(os.path.join(tmpdir, hparams_file))