replaces any with unknown, adds test to show how optional chaining of…

… array items can result in undefined even though typescript says its not

x-pack/legacy/plugins/siem/server/lib/detection_engine/routes/rules/find_rules_status_route.ts

@@ -59,6 +59,10 @@ export const createFindRulesStatusRoute = (getClients: GetScopedClients): Hapi.S
           searchFields: ['alertId'],
         });
         const accumulated = await acc;
+
+        // Array accessors can result in undefined but
+        // this is not represented in typescript for some reason,
+        // https://github.com/Microsoft/TypeScript/issues/11122
         const currentStatus = convertToSnakeCase<IRuleStatusAttributes>(
           lastFiveErrorsForId.saved_objects[0]?.attributes
         );

x-pack/legacy/plugins/siem/server/lib/detection_engine/routes/utils.test.ts

@@ -6,6 +6,8 @@
 
 import Boom from 'boom';
 
+import { SavedObjectsFindResponse } from 'kibana/server';
+import { IRuleSavedAttributesSavedObjectAttributes, IRuleStatusAttributes } from '../rules/types';
 import {
   transformError,
   transformBulkError,
@@ -323,5 +325,19 @@ describe('utils', () => {
       const values = {};
       expect(convertToSnakeCase(values)).toEqual({});
     });
+    it('returns null when passed in undefined', () => {
+      // Array accessors can result in undefined but
+      // this is not represented in typescript for some reason,
+      // https://github.com/Microsoft/TypeScript/issues/11122
+      const values: SavedObjectsFindResponse<IRuleSavedAttributesSavedObjectAttributes> = {
+        page: 0,
+        per_page: 5,
+        total: 0,
+        saved_objects: [],
+      };
+      expect(
+        convertToSnakeCase<IRuleStatusAttributes>(values.saved_objects[0]?.attributes) // this is undefined, but it says it's not
+      ).toEqual(null);
+    });
   });
 });

x-pack/legacy/plugins/siem/server/lib/detection_engine/routes/utils.ts

@@ -222,8 +222,9 @@ export const getIndex = (getSpaceId: () => string, config: LegacyServices['confi
   return `${signalsIndex}-${spaceId}`;
 };
 
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-export const convertToSnakeCase = <T extends Record<string, any>>(obj: T): Partial<T> | null => {
+export const convertToSnakeCase = <T extends Record<string, unknown>>(
+  obj: T
+): Partial<T> | null => {
   if (!obj) {
     return null;
   }