From fafe4299f51c5c9991459f4a83ff96c3bfe23b02 Mon Sep 17 00:00:00 2001
From: Tianshu Wang <wang@tianshu.me>
Date: Fri, 11 Nov 2022 19:21:22 +0800
Subject: [PATCH] Make sure save_dir can be empty str (#15638)

(cherry picked from commit c53dc205ed0c1911295a2f741781920b840808d7)
---
 src/pytorch_lightning/callbacks/model_checkpoint.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/pytorch_lightning/callbacks/model_checkpoint.py b/src/pytorch_lightning/callbacks/model_checkpoint.py
index 8d0596e3bdccdc..2e7b9bbb27b293 100644
--- a/src/pytorch_lightning/callbacks/model_checkpoint.py
+++ b/src/pytorch_lightning/callbacks/model_checkpoint.py
@@ -574,7 +574,10 @@ def __resolve_ckpt_dir(self, trainer: "pl.Trainer") -> _PATH:
             return self.dirpath
 
         if len(trainer.loggers) > 0:
-            save_dir = trainer.loggers[0].save_dir or trainer.default_root_dir
+            if trainer.loggers[0].save_dir is not None:
+                save_dir = trainer.loggers[0].save_dir
+            else:
+                save_dir = trainer.default_root_dir
             name = trainer.loggers[0].name
             version = trainer.loggers[0].version
             version = version if isinstance(version, str) else f"version_{version}"