17632 FIX local: Don't create crash reports for invalid user data

CMK-22111

Change-Id: I47b0c45d72da344056fb4e35b8a4b928ad3c30d6

Author: mo-ki

.werks/17632

@@ -0,0 +1,13 @@
+Title: local: Don't create crash reports for invalid user data
+Class: fix
+Compatible: compat
+Component: checks
+Date: 1742560138
+Edition: cre
+Level: 1
+Version: 2.2.0p41
+
+The check plugin dealing with the output of local checks (deployed on the monitored host) created crash reports in case it encountered invalid data.
+These crash reports are not actionable for Checkmk.
+
+The service now goes to an UNKNOWN state, providing some details in the service page.

cmk/base/plugins/agent_based/local.py

@@ -400,9 +400,17 @@ def discover_local(section: LocalSection) -> DiscoveryResult:
 
 def check_local(item: str, params: Mapping[str, Any], section: LocalSection) -> LocalCheckResult:
     if (local_error := section.errors.get(item)) is not None:
-        raise ValueError(
-            (f'Invalid local check line: "{local_error.output}". Reason: {local_error.reason}')
+        # Do *not* raise an exception here. Users will send us crash reports if we do.
+        yield Result(
+            state=State.UNKNOWN,
+            summary=f"Invalid data: {local_error.output!r}",
+            details=(
+                "The monitoring site got invalid data from a local check on the monitored host.\n"
+                f"Invalid data: {local_error.output!r}\n"
+                f"Reason: {local_error.reason}"
+            ),
         )
+        return
 
     local_result = section.data.get(item)
     if local_result is None:

tests/unit/cmk/base/plugins/agent_based/test_local.py

@@ -31,6 +31,25 @@ def test_invalid_metric_name_does_not_crash() -> None:
     ]
 
 
+def test_error_does_not_raise() -> None:
+    assert list(
+        local.check_local(
+            "MyService",
+            {},
+            local.parse_local([["ARGL", "MyService", "-", "Whopwhop"]]),
+        )
+    ) == [
+        Result(
+            state=State.UNKNOWN,
+            summary="Invalid data: 'ARGL MyService - Whopwhop'",
+            details=(
+                "The monitoring site got invalid data from a local check on the monitored host.\n"
+                "Invalid data: 'ARGL MyService - Whopwhop'\nReason: Invalid plugin status ARGL."
+            ),
+        )
+    ]
+
+
 @pytest.mark.parametrize(
     "check_line,expected_components",
     [