Emit warning on incorrect Objective name

CHANGELOG.md

@@ -19,6 +19,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 - [💥 Breaking change] `init` function is now required to be called before using autometrics (#89)
 - Prometheus exporters are now configured via `init` function (#89)
+- `Objective`s will now emit a warning when name contains characters other than alphanumeric and dash (#99)
 
 ### Deprecated
 

src/autometrics/objectives.py

@@ -1,4 +1,7 @@
+import logging
+
 from enum import Enum
+from re import match
 from typing import Optional, Tuple
 
 
@@ -89,3 +92,9 @@ def __init__(
         self.name = name
         self.success_rate = success_rate
         self.latency = latency
+
+        # Check that name only contains alphanumeric characters and hyphens
+        if match(r"^[\w-]+$", name) is None:
+            logging.getLogger().warning(
+                f"Objective name '{name}' contains invalid characters. Only alphanumeric characters and hyphens are allowed."
+            )

src/autometrics/test_objectives.py

@@ -0,0 +1,16 @@
+import logging
+
+from autometrics.objectives import Objective
+
+
+def test_objective_name_warning(caplog):
+    """Test that a warning is logged when an objective name contains invalid characters."""
+    caplog.set_level(logging.WARNING)
+    caplog.clear()
+    Objective("Incorrect name.")
+    assert len(caplog.records) == 1
+    assert caplog.records[0].levelname == "WARNING"
+    assert "contains invalid characters" in caplog.records[0].message
+    caplog.clear()
+    Objective("correct-name-123")
+    assert len(caplog.records) == 0