test(prometheus): check emitted labels instead of wrapper types, close the admission match

The exclude-labels test now emits through the spend and provider budget
metrics and checks the scrape keeps all their labels. The admission match
arms end in assert_never so the match is exhaustive.

litellm/integrations/prometheus.py

@@ -15,7 +15,7 @@ from types import MappingProxyType
 from typing import TYPE_CHECKING, Any, Final, Literal, Protocol, TypeAlias, TypeVar, cast
 
 from pydantic import BaseModel
-from typing_extensions import ReadOnly, TypedDict
+from typing_extensions import ReadOnly, TypedDict, assert_never
 
 import litellm
 from litellm._internal_context import with_service_target
@@ -229,12 +229,14 @@ class _LabeledMetric:
     def remove(self, *labelvalues: object) -> None:
         match self._tracker:
             case SharedPrometheusSeriesAdmissions():
-                return
+                pass
             case BoundedPrometheusSeriesTracker():
                 kept_values: Final = self._kept_values(labelvalues)
                 with self._tracker.lock:
                     self._tracker.forget_series(self._metric_name, kept_values)
                     self._metric.remove(*kept_values)
+            case _:
+                assert_never(self._tracker)
 
     def _admits(self, kept_values: tuple[str, ...]) -> bool:
         match self._tracker:
@@ -246,6 +248,8 @@ class _LabeledMetric:
                 return self._tracker.admit_series(
                     metric=self._metric, metric_name=self._metric_name, label_values=kept_values, limits=self._limits
                 )
+            case _:
+                assert_never(self._tracker)
 
     def _kept_values(self, values: tuple[object, ...]) -> tuple[str, ...]:
         return tuple(

tests/unit/enterprise/integrations/test_prometheus.py

@@ -689,9 +689,8 @@ def test_exclude_only_hardcoded_label_drops_all_labels(reset_prometheus_exclude_
 
 
 def test_exclude_labels_does_not_touch_unrelated_metrics(reset_prometheus_exclude_settings):
-    """A metric that never declares the excluded label is left as a plain prometheus metric,
-    not wrapped, so no behavior changes for it."""
-    from litellm.integrations.prometheus import _LabeledMetric
+    """A metric that never declares the excluded label keeps every one of its own labels in the scrape."""
+    from prometheus_client import generate_latest
 
     clear_prometheus_registry()
     litellm.prometheus_metrics_config = None
@@ -699,10 +698,15 @@ def test_exclude_labels_does_not_touch_unrelated_metrics(reset_prometheus_exclud
     litellm.prometheus_exclude_labels = ["guardrail_name"]
 
     logger = PrometheusLogger()
+    spend_labels = {name: f"{name}-value" for name in PrometheusMetricLabels.get_labels("litellm_spend_metric")}
+    logger.litellm_spend_metric.labels(**spend_labels).inc(1.5)
+    logger.litellm_provider_remaining_budget_metric.labels("anthropic").set(5.0)
 
-    assert not isinstance(logger.litellm_spend_metric, _LabeledMetric)
-    assert not isinstance(logger.litellm_provider_remaining_budget_metric, _LabeledMetric)
-    assert isinstance(logger.litellm_guardrail_latency_metric, _LabeledMetric)
+    scrape = generate_latest(REGISTRY).decode()
+    spend_line = next(line for line in scrape.splitlines() if line.startswith("litellm_spend_metric_total{"))
+    assert all(f'{name}="{value}"' in spend_line for name, value in spend_labels.items())
+    assert spend_line.endswith(" 1.5")
+    assert 'litellm_provider_remaining_budget_metric{api_provider="anthropic"} 5.0' in scrape
 
 
 # ==============================================================================