refactor(pipeline): Improve state file naming conventions for clarity and uniqueness

- Enhanced state file naming to include the processor's sanitized name, ensuring uniqueness when multiple processors are saved in the same directory.
- Updated tests to reflect changes in state file naming, verifying that filenames now include the processor name and step indices to prevent conflicts.
- Added a new test to validate state file naming when using multiple processors, ensuring distinct filenames for each processor's state files.

src/lerobot/processor/pipeline.py

@@ -416,12 +416,13 @@ class RobotProcessor(ModelHubMixin):
         """
         os.makedirs(destination_path, exist_ok=True)
 
-        # Determine config filename - sanitize the processor name for filesystem
+        # Sanitize processor name for use in filenames
-        if config_filename is None:
+        import re
-            # Sanitize name - replace any character that's not alphanumeric or underscore
-            import re
 
-            sanitized_name = re.sub(r"[^a-zA-Z0-9_]", "_", self.name.lower())
+        sanitized_name = re.sub(r"[^a-zA-Z0-9_]", "_", self.name.lower())
+
+        # Use sanitized name for config if not provided
+        if config_filename is None:
             config_filename = f"{sanitized_name}.json"
 
         config: dict[str, Any] = {
@@ -463,12 +464,12 @@ class RobotProcessor(ModelHubMixin):
                     for key, tensor in state.items():
                         cloned_state[key] = tensor.clone()
 
-                    # Always include step index to ensure unique filenames
+                    # Include pipeline name and step index to ensure unique filenames
-                    # This prevents conflicts when the same processor type is used multiple times
+                    # This prevents conflicts when multiple processors are saved in the same directory
                     if registry_name:
-                        state_filename = f"step_{step_index}_{registry_name}.safetensors"
+                        state_filename = f"{sanitized_name}_step_{step_index}_{registry_name}.safetensors"
                     else:
-                        state_filename = f"step_{step_index}.safetensors"
+                        state_filename = f"{sanitized_name}_step_{step_index}.safetensors"
 
                     save_file(cloned_state, os.path.join(destination_path, state_filename))
                     step_entry["state_file"] = state_filename

tests/processor/test_pipeline.py

@@ -630,7 +630,7 @@ def test_mixed_json_and_tensor_state():
 
         # Check that both config and state files were created
         config_path = Path(tmp_dir) / "robotprocessor.json"  # Default name is "RobotProcessor"
-        state_path = Path(tmp_dir) / "step_0.safetensors"
+        state_path = Path(tmp_dir) / "robotprocessor_step_0.safetensors"
         assert config_path.exists()
         assert state_path.exists()
 
@@ -1735,7 +1735,7 @@ def test_error_multiple_configs_no_filename():
 
 
 def test_state_file_naming_with_indices():
-    """Test that state files include step indices to avoid conflicts."""
+    """Test that state files include pipeline name and step indices to avoid conflicts."""
     # Create multiple steps of same type with state
     step1 = MockStepWithTensorState(name="norm1", window_size=5)
     step2 = MockStepWithTensorState(name="norm2", window_size=10)
@@ -1755,14 +1755,18 @@ def test_state_file_naming_with_indices():
         state_files = sorted(Path(tmp_dir).glob("*.safetensors"))
         assert len(state_files) == 3
 
-        # Files should be named with indices
+        # Files should be named with pipeline name prefix and indices
-        expected_names = ["step_0.safetensors", "step_1.safetensors", "step_2.safetensors"]
+        expected_names = [
+            "robotprocessor_step_0.safetensors",
+            "robotprocessor_step_1.safetensors",
+            "robotprocessor_step_2.safetensors",
+        ]
         actual_names = [f.name for f in state_files]
         assert actual_names == expected_names
 
 
 def test_state_file_naming_with_registry():
-    """Test state file naming for registered steps includes both index and name."""
+    """Test state file naming for registered steps includes pipeline name, index and registry name."""
 
     # Register a test step
     @ProcessorStepRegistry.register("test_stateful_step")
@@ -1799,10 +1803,10 @@ def test_state_file_naming_with_registry():
             state_files = sorted(Path(tmp_dir).glob("*.safetensors"))
             assert len(state_files) == 2
 
-            # Should include both index and registry name
+            # Should include pipeline name, index and registry name
             expected_names = [
-                "step_0_test_stateful_step.safetensors",
+                "robotprocessor_step_0_test_stateful_step.safetensors",
-                "step_1_test_stateful_step.safetensors",
+                "robotprocessor_step_1_test_stateful_step.safetensors",
             ]
             actual_names = [f.name for f in state_files]
             assert actual_names == expected_names
@@ -1995,6 +1999,42 @@ def test_config_filename_special_characters():
         assert json_files[0].name == expected_name
 
 
+def test_state_file_naming_with_multiple_processors():
+    """Test that state files are properly prefixed with pipeline names to avoid conflicts."""
+    # Create two processors with state
+    step1 = MockStepWithTensorState(name="norm", window_size=5)
+    preprocessor = RobotProcessor([step1], name="PreProcessor")
+
+    step2 = MockStepWithTensorState(name="norm", window_size=10)
+    postprocessor = RobotProcessor([step2], name="PostProcessor")
+
+    # Process some data to create state
+    for i in range(3):
+        transition = create_transition(reward=float(i))
+        preprocessor(transition)
+        postprocessor(transition)
+
+    with tempfile.TemporaryDirectory() as tmp_dir:
+        # Save both processors to the same directory
+        preprocessor.save_pretrained(tmp_dir)
+        postprocessor.save_pretrained(tmp_dir)
+
+        # Check that all files exist and are distinct
+        assert (Path(tmp_dir) / "preprocessor.json").exists()
+        assert (Path(tmp_dir) / "postprocessor.json").exists()
+        assert (Path(tmp_dir) / "preprocessor_step_0.safetensors").exists()
+        assert (Path(tmp_dir) / "postprocessor_step_0.safetensors").exists()
+
+        # Load both back and verify they work correctly
+        loaded_pre = RobotProcessor.from_pretrained(tmp_dir, config_filename="preprocessor.json")
+        loaded_post = RobotProcessor.from_pretrained(tmp_dir, config_filename="postprocessor.json")
+
+        assert loaded_pre.name == "PreProcessor"
+        assert loaded_post.name == "PostProcessor"
+        assert loaded_pre.steps[0].window_size == 5
+        assert loaded_post.steps[0].window_size == 10
+
+
 def test_override_with_device_strings():
     """Test overriding device parameters with string values."""