fix: keyError when Prometheuse metric name is normalized

prom_metric_name was only changed for _create_prometheus_metric and
not _add_prometheus_sample.

mqtt_exporter/main.py

@@ -86,18 +86,16 @@ def _create_prometheus_metric(prom_metric_name):
         if settings.MQTT_EXPOSE_CLIENT_ID:
             labels.append("client_id")
 
-        prom_metric_name = _normalize_prometheus_metric_name(prom_metric_name)
-
-        try:
-            prom_metrics[prom_metric_name] = Gauge(
-                prom_metric_name, "metric generated from MQTT message.", labels
-            )
-            LOG.info("creating prometheus metric: %s", prom_metric_name)
-        except ValueError as error:
-            LOG.error("unable to create prometheus metric '%s': %s", prom_metric_name, error)
+        prom_metrics[prom_metric_name] = Gauge(
+            prom_metric_name, "metric generated from MQTT message.", labels
+        )
+        LOG.info("creating prometheus metric: %s", prom_metric_name)
 
 
 def _add_prometheus_sample(topic, prom_metric_name, metric_value, client_id):
+    if prom_metric_name not in prom_metrics:
+        return
+
     labels = {settings.TOPIC_LABEL: topic}
     if settings.MQTT_EXPOSE_CLIENT_ID:
         labels["client_id"] = client_id
@@ -165,7 +163,12 @@ def _parse_metrics(data, topic, client_id, prefix=""):
             .replace("/", "_")
         )
         prom_metric_name = re.sub(r"\((.*?)\)", "", prom_metric_name)
-        _create_prometheus_metric(prom_metric_name)
+        prom_metric_name = _normalize_prometheus_metric_name(prom_metric_name)
+        try:
+            _create_prometheus_metric(prom_metric_name)
+        except ValueError as error:
+            LOG.error("unable to create prometheus metric '%s': %s", prom_metric_name, error)
+            return
 
         # expose the sample to prometheus
         _add_prometheus_sample(topic, prom_metric_name, metric_value, client_id)

tests/functional/test_expose_metrics.py

@@ -20,10 +20,10 @@ def _exec(client_id, mocker):
     userdata = {"client_id": client_id}
     msg = mocker.Mock()
     msg.topic = "zigbee2mqtt/garage"
-    msg.payload = '{"temperature": "23.5", "humidity": "40.5"}'
+    msg.payload = '{"temperature°C": "23.5", "humidity": "40.5"}'
     main.expose_metrics(None, userdata, msg)
 
-    temperatures = main.prom_metrics["mqtt_temperature"].collect()
+    temperatures = main.prom_metrics["mqtt_temperatureC"].collect()
     humidity = main.prom_metrics["mqtt_humidity"].collect()
 
     return temperatures, humidity