Fix support for `ModelCheckpoint` monitors with dots (#12783)

Co-authored-by: Carlos Mocholí <carlossmocholi@gmail.com>

CHANGELOG.md

@@ -135,7 +135,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - When using custom DataLoaders in LightningDataModule, multiple inheritance is resolved properly ([#12716](https://github.com/PyTorchLightning/pytorch-lightning/pull/12716))
 
 
--
+- Fixed support for `ModelCheckpoint` monitors with dots ([#12783](https://github.com/PyTorchLightning/pytorch-lightning/pull/12783))
 
 
 ## [1.6.1] - 2022-04-13

pytorch_lightning/callbacks/model_checkpoint.py

@@ -517,9 +517,12 @@ class ModelCheckpoint(Callback):
                 if auto_insert_metric_name:
                     filename = filename.replace(group, name + "={" + name)
 
+                # support for dots: https://stackoverflow.com/a/7934969
+                filename = filename.replace(group, f"{{0[{name}]")
+
                 if name not in metrics:
                     metrics[name] = 0
-            filename = filename.format(**metrics)
+            filename = filename.format(metrics)
 
         if prefix:
             filename = cls.CHECKPOINT_JOIN_CHAR.join([prefix, filename])

tests/checkpointing/test_model_checkpoint.py

@@ -452,6 +452,12 @@ def test_model_checkpoint_format_checkpoint_name(tmpdir):
     )
     assert ckpt_name == "epoch=003-val_acc=0.03"
 
+    # dots in the metric name
+    ckpt_name = ModelCheckpoint._format_checkpoint_name(
+        "mAP@0.50={val/mAP@0.50:.4f}", {"val/mAP@0.50": 0.2}, auto_insert_metric_name=False
+    )
+    assert ckpt_name == "mAP@0.50=0.2000"
+
 
 class ModelCheckpointExtensionTest(ModelCheckpoint):
     FILE_EXTENSION = ".tpkc"