Deprecate reporting.index setting

docs/settings/reporting-settings.asciidoc

@@ -261,7 +261,9 @@ For information about {kib} memory limits, see <<production, using {kib} in a pr
 [cols="2*<"]
 |===
 | `xpack.reporting.index`
-  | Reporting uses a weekly index in {es} to store the reporting job and
+  | *deprecated* This setting is deprecated and will be removed in 8.0. Multitenancy by changing
+  `kibana.index` will not be supported starting in 8.0. See https://ela.st/kbn-remove-legacy-multitenancy[8.0 Breaking Changes]
+  for more details. Reporting uses a weekly index in {es} to store the reporting job and
   the report content. The index is automatically created if it does not already
   exist. Configure this to a unique value, beginning with `.reporting-`, for every
   {kib} instance that has a unique <<kibana-index, `kibana.index`>> setting. Defaults to `.reporting`.

x-pack/plugins/reporting/server/config/index.test.ts

@@ -0,0 +1,42 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { config } from './index';
+import { applyDeprecations, configDeprecationFactory } from '@kbn/config';
+
+const CONFIG_PATH = 'xpack.reporting';
+
+const applyReportingDeprecations = (settings: Record<string, any> = {}) => {
+  const deprecations = config.deprecations!(configDeprecationFactory);
+  const deprecationMessages: string[] = [];
+  const _config: any = {};
+  _config[CONFIG_PATH] = settings;
+  const migrated = applyDeprecations(
+    _config,
+    deprecations.map((deprecation) => ({
+      deprecation,
+      path: CONFIG_PATH,
+    })),
+    (msg) => deprecationMessages.push(msg)
+  );
+  return {
+    messages: deprecationMessages,
+    migrated,
+  };
+};
+
+describe('deprecations', () => {
+  ['.foo', '.reporting'].forEach((index) => {
+    it('logs a warning if index is set', () => {
+      const { messages } = applyReportingDeprecations({ index });
+      expect(messages).toMatchInlineSnapshot(`
+        Array [
+          "\\"xpack.reporting.index\\" is deprecated. Multitenancy by changing \\"kibana.index\\" will not be supported starting in 8.0. See https://ela.st/kbn-remove-legacy-multitenancy for more details",
+        ]
+      `);
+    });
+  });
+});

x-pack/plugins/reporting/server/config/index.ts

@@ -4,6 +4,7 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
+import { get } from 'lodash';
 import { PluginConfigDescriptor } from 'kibana/server';
 import { ConfigSchema, ReportingConfigType } from './schema';
 export { buildConfig } from './config';
@@ -20,5 +21,14 @@ export const config: PluginConfigDescriptor<ReportingConfigType> = {
     unused('poll.jobCompletionNotifier.intervalErrorMultiplier'),
     unused('poll.jobsRefresh.intervalErrorMultiplier'),
     unused('kibanaApp'),
+    (settings, fromPath, log) => {
+      const reporting = get(settings, fromPath);
+      if (reporting?.index) {
+        log(
+          `"${fromPath}.index" is deprecated. Multitenancy by changing "kibana.index" will not be supported starting in 8.0. See https://ela.st/kbn-remove-legacy-multitenancy for more details`
+        );
+      }
+      return settings;
+    },
   ],
 };