Remove nameless collectors from the registry on unregister

When a collector is registered under support_collectors_without_names
with no metric names, register() appends it to _collectors_without_names
in addition to the usual bookkeeping. unregister() only cleaned up
_collector_to_names and _names_to_collectors, so the collector stayed in
_collectors_without_names and kept being collected.

A normal collect() no longer returned the collector's metrics, but
RestrictedRegistry.collect() -- which seeds its collector set from
_collectors_without_names -- still did, so an unregistered collector's
samples reappeared under restricted_registry(). unregister() now also
drops the collector from that list.

Add test_unregister_removes_no_names_collector, asserting a nameless
collector is no longer collected by a restricted registry after it has
been unregistered.

Signed-off-by: Sean Kim <skim8705@gmail.com>

Author: sean-kim05

prometheus_client/registry.py

@@ -61,6 +61,8 @@ def unregister(self, collector: Collector) -> None:
             for name in self._collector_to_names[collector]:
                 del self._names_to_collectors[name]
             del self._collector_to_names[collector]
+            if collector in self._collectors_without_names:
+                self._collectors_without_names.remove(collector)
 
     def _get_names(self, collector):
         """Get names of timeseries the collector produces and clashes with."""

tests/test_core.py

@@ -960,6 +960,21 @@ def test_unregister_works(self):
         registry.unregister(s)
         Gauge('s_count', 'help', registry=registry)
 
+    def test_unregister_removes_no_names_collector(self):
+        registry = CollectorRegistry(support_collectors_without_names=True)
+
+        class NamelessCollector:
+            def collect(self):
+                return [GaugeMetricFamily('foo', 'help', value=42)]
+
+        collector = NamelessCollector()
+        registry.register(collector)
+        registry.unregister(collector)
+        # A nameless collector must be removed from the collectors-without-names
+        # list too, otherwise a restricted registry keeps collecting it after it
+        # was unregistered.
+        self.assertEqual([], list(registry.restricted_registry(['foo']).collect()))
+
     def custom_collector(self, metric_family, registry):
         class CustomCollector:
             def collect(self):