[Controls] Omit null values from controlConfig if they cause validation errors (elastic#253131)

## Summary

Some pre-9.4 controls store values we've defined as `maybe` as `null`
instead of `undefined`. This PR strips null values during migration if
they're causing schema validation errors.

This was causing some controls to fail to migrate, and prevented
dashboards on serverless from being duplicated.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Author: Zacqary

src/platform/packages/shared/controls/controls-schemas/src/legacy_types.ts

@@ -44,13 +44,13 @@ export type LegacyStoredOptionsListExplicitInput = LegacyStoredDataControlState
     hideExists?: boolean;
     hideSort?: boolean;
   };
-  exclude?: boolean;
-  existsSelected?: boolean;
-  runPastTimeout?: boolean;
-  searchTechnique?: string;
-  selectedOptions?: Array<string | number>;
-  singleSelect?: boolean;
-  sort?: { by: string; direction: string };
+  exclude?: boolean | null;
+  existsSelected?: boolean | null;
+  runPastTimeout?: boolean | null;
+  searchTechnique?: string | null;
+  selectedOptions?: Array<string | number> | null;
+  singleSelect?: boolean | null;
+  sort?: { by: string; direction: string } | null;
 };
 
 export type LegacyStoredRangeSliderExplicitInput = LegacyStoredDataControlState & {

src/platform/plugins/shared/controls/server/transforms/options_list_control_transforms.test.ts

@@ -0,0 +1,68 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+import { createEmbeddableSetupMock } from '@kbn/embeddable-plugin/server/mocks';
+import { registerOptionsListControlTransforms } from './options_list_control_transforms';
+import type { DrilldownTransforms } from '@kbn/embeddable-plugin/common';
+
+const REF_NAME = 'test-data-view';
+
+const baseState = {
+  dataViewRefName: REF_NAME,
+  field_name: 'test',
+  title: 'Test',
+};
+
+const panelReferences = [{ name: REF_NAME, type: 'index-pattern', id: 'data-view-id' }];
+
+const getTransformOut = () => {
+  const embeddable = createEmbeddableSetupMock();
+  registerOptionsListControlTransforms(embeddable);
+
+  const [, transformsSetup] = embeddable.registerTransforms.mock.calls[0];
+  const { transformOut } = transformsSetup.getTransforms!({} as DrilldownTransforms);
+  return transformOut!;
+};
+
+describe('options list control transforms', () => {
+  describe('transformOut', () => {
+    const transformOut = getTransformOut();
+
+    it('omits null values while keeping non-null values', () => {
+      const result = transformOut(
+        {
+          ...baseState,
+          exclude: true,
+          sort: null,
+          existsSelected: null,
+          runPastTimeout: null,
+          searchTechnique: 'prefix',
+          selectedOptions: ['val'],
+          singleSelect: null,
+        },
+        panelReferences,
+        undefined,
+        undefined
+      );
+
+      expect(result).toMatchInlineSnapshot(`
+        Object {
+          "data_view_id": "data-view-id",
+          "exclude": true,
+          "field_name": "test",
+          "search_technique": "prefix",
+          "selected_options": Array [
+            "val",
+          ],
+          "title": "Test",
+        }
+      `);
+    });
+  });
+});

src/platform/plugins/shared/controls/server/transforms/options_list_control_transforms.ts

@@ -9,12 +9,13 @@
 
 import type { Reference } from '@kbn/content-management-utils';
 import { OPTIONS_LIST_CONTROL } from '@kbn/controls-constants';
-import type {
-  LegacyStoredOptionsListExplicitInput,
-  OptionsListDSLControlState,
+import {
+  type LegacyStoredOptionsListExplicitInput,
+  type OptionsListDSLControlState,
 } from '@kbn/controls-schemas';
 import type { EmbeddableSetup } from '@kbn/embeddable-plugin/server';
 import { convertCamelCasedKeysToSnakeCase } from '@kbn/presentation-publishing';
+import { omitBy } from 'lodash';
 import { transformDataControlIn, transformDataControlOut } from './data_control_transforms';
 
 const OPTIONS_LIST_REF_NAME = 'optionsListDataView' as const;
@@ -69,17 +70,23 @@ export const registerOptionsListControlTransforms = (embeddable: EmbeddableSetup
         } = convertCamelCasedKeysToSnakeCase<LegacyStoredOptionsListExplicitInput>(
           state as LegacyStoredOptionsListExplicitInput
         );
-        return {
-          ...dataControlState,
-          exclude,
-          ...{ sort: sort as OptionsListDSLControlState['sort'] },
-          exists_selected,
-          display_settings,
-          run_past_timeout,
-          search_technique: search_technique as OptionsListDSLControlState['search_technique'],
-          selected_options,
-          single_select,
-        };
+
+        // Optional legacy props may have been stored as `null` instead of `undefined`, so drop all
+        // null or undefined keys
+        return omitBy(
+          {
+            ...dataControlState,
+            exclude,
+            sort,
+            exists_selected,
+            display_settings,
+            run_past_timeout,
+            search_technique,
+            selected_options,
+            single_select,
+          },
+          (v) => v === null || v === undefined
+        ) as OptionsListDSLControlState;
       },
     }),
   });