notifications: catch errors in apply_matchers

Change-Id: I128d8a630d35f3c289fe2402c9173d2acd9cc529
JIRA-Ref: SUP-21074

cmk/base/events.py

@@ -12,6 +12,7 @@
 import socket
 import sys
 import time
+import traceback
 from collections.abc import Callable, Iterable, Mapping
 from typing import Any, cast
 from urllib.parse import quote, urlencode
@@ -485,7 +486,10 @@ def apply_matchers(
     all_timeperiods: TimeperiodSpecs,
 ) -> str | None:
     for matcher in matchers:
-        result = matcher(rule, context, analyse, all_timeperiods)
+        try:
+            result = matcher(rule, context, analyse, all_timeperiods)
+        except Exception:
+            return f"Error in matcher: {traceback.format_exc()}"
         if result is not None:
             return result
     return None

tests/unit/cmk/base/test_events.py

@@ -24,6 +24,7 @@
 from cmk.base.events import (
     _update_enriched_context_from_notify_host_file,
     add_to_event_context,
+    apply_matchers,
     convert_proxy_params,
     event_match_hosttags,
     raw_context_from_string,
@@ -484,3 +485,32 @@ def test_convert_proxy_params(
 ) -> None:
     params_dict = convert_proxy_params(params)
     assert params_dict["proxy_url"] == expected
+
+
+def test_apply_matchers_catches_errors() -> None:
+    rule = EventRule(
+        rule_id=NotificationRuleID("1"),
+        allow_disable=False,
+        contact_all=False,
+        contact_all_with_email=False,
+        contact_object=False,
+        description="Test rule",
+        disabled=False,
+        notify_plugin=("mail", NotificationParameterID("parameter_id")),
+    )
+
+    def raise_error() -> None:
+        raise ValueError("This is a test")
+
+    why_not = apply_matchers(
+        [
+            lambda *args, **kw: raise_error(),
+        ],
+        rule,
+        context={},
+        analyse=False,
+        all_timeperiods={},
+    )
+
+    assert isinstance(why_not, str)
+    assert "ValueError: This is a test" in why_not