[Runtime field editor] Fix preview error when not enough privileges (#115070)

src/plugins/index_pattern_field_editor/__jest__/client_integration/field_editor_flyout_preview.test.ts

@@ -366,6 +366,7 @@ describe('Field editor Preview panel', () => {
           subTitle: 'First doc - subTitle',
           title: 'First doc - title',
         },
+        documentId: '001',
         index: 'testIndex',
         script: {
           source: 'echo("hello")',

src/plugins/index_pattern_field_editor/public/components/preview/field_preview_context.tsx

@@ -335,6 +335,7 @@ export const FieldPreviewProvider: FunctionComponent = ({ children }) => {
       document: params.document!,
       context: `${params.type!}_field` as FieldPreviewContext,
       script: params.script!,
+      documentId: currentDocId,
     });
 
     if (currentApiCall !== previewCount.current) {

src/plugins/index_pattern_field_editor/public/lib/api.ts

@@ -16,11 +16,13 @@ export const initApi = (httpClient: HttpSetup) => {
     context,
     script,
     document,
+    documentId,
   }: {
     index: string;
     context: FieldPreviewContext;
     script: { source: string } | null;
     document: Record<string, any>;
+    documentId: string;
   }) => {
     return sendRequest<FieldPreviewResponse>(httpClient, {
       path: `${API_BASE_PATH}/field_preview`,
@@ -30,6 +32,7 @@ export const initApi = (httpClient: HttpSetup) => {
         context,
         script,
         document,
+        documentId,
       },
     });
   };

src/plugins/index_pattern_field_editor/server/routes/field_preview.ts

@@ -6,8 +6,8 @@
  * Side Public License, v 1.
  */
 
+import { estypes } from '@elastic/elasticsearch';
 import { schema } from '@kbn/config-schema';
-import { HttpResponsePayload } from 'kibana/server';
 
 import { API_BASE_PATH } from '../../common/constants';
 import { RouteDependencies } from '../types';
@@ -26,6 +26,7 @@ const bodySchema = schema.object({
     schema.literal('long_field'),
   ]),
   document: schema.object({}, { unknowns: 'allow' }),
+  documentId: schema.string(),
 });
 
 export const registerFieldPreviewRoute = ({ router }: RouteDependencies): void => {
@@ -39,30 +40,41 @@ export const registerFieldPreviewRoute = ({ router }: RouteDependencies): void =
     async (ctx, req, res) => {
       const { client } = ctx.core.elasticsearch;
 
-      const body = JSON.stringify({
-        script: req.body.script,
-        context: req.body.context,
-        context_setup: {
-          document: req.body.document,
-          index: req.body.index,
-        } as any,
-      });
+      const type = req.body.context.split('_field')[0] as estypes.MappingRuntimeFieldType;
+      const body = {
+        runtime_mappings: {
+          my_runtime_field: {
+            type,
+            script: req.body.script,
+          },
+        },
+        size: 1,
+        query: {
+          term: {
+            _id: req.body.documentId,
+          },
+        },
+        fields: ['my_runtime_field'],
+      };
 
       try {
-        const response = await client.asCurrentUser.scriptsPainlessExecute({
-          // @ts-expect-error `ExecutePainlessScriptRequest.body` does not allow `string`
+        const response = await client.asCurrentUser.search({
+          index: req.body.index,
           body,
         });
 
-        const fieldValue = response.body.result as any[] as HttpResponsePayload;
+        const fieldValue = response.body.hits.hits[0]?.fields?.my_runtime_field ?? '';
 
         return res.ok({ body: { values: fieldValue } });
-      } catch (error) {
+      } catch (error: any) {
         // Assume invalid painless script was submitted
         // Return 200 with error object
         const handleCustomError = () => {
           return res.ok({
-            body: { values: [], ...error.body },
+            body: {
+              values: [],
+              error: error.body.error.failed_shards[0]?.reason ?? {},
+            },
           });
         };
 

test/api_integration/apis/index_pattern_field_editor/field_preview.ts

@@ -12,11 +12,14 @@ import { FtrProviderContext } from '../../ftr_provider_context';
 import { API_BASE_PATH } from './constants';
 
 const INDEX_NAME = 'api-integration-test-field-preview';
+const DOC_ID = '1';
 
 export default function ({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
   const es = getService('es');
 
+  const document = { foo: 1, bar: 'hello' };
+
   const createIndex = async () => {
     await es.indices.create({
       index: INDEX_NAME,
@@ -35,6 +38,15 @@ export default function ({ getService }: FtrProviderContext) {
     });
   };
 
+  const addDoc = async () => {
+    await es.index({
+      index: INDEX_NAME,
+      id: DOC_ID,
+      body: document,
+      refresh: 'wait_for',
+    });
+  };
+
   const deleteIndex = async () => {
     await es.indices.delete({
       index: INDEX_NAME,
@@ -42,12 +54,13 @@ export default function ({ getService }: FtrProviderContext) {
   };
 
   describe('Field preview', function () {
-    before(async () => await createIndex());
+    before(async () => {
+      await createIndex();
+      await addDoc();
+    });
     after(async () => await deleteIndex());
 
     describe('should return the script value', () => {
-      const document = { foo: 1, bar: 'hello' };
-
       const tests = [
         {
           context: 'keyword_field',
@@ -77,6 +90,7 @@ export default function ({ getService }: FtrProviderContext) {
           const payload = {
             script: test.script,
             document,
+            documentId: DOC_ID,
             context: test.context,
             index: INDEX_NAME,
           };