refactor: apply review suggestions

Signed-off-by: Camila Belo <camilaibs@gmail.com>

.changeset/two-owls-cry.md

@@ -1,6 +1,5 @@
 ---
 '@backstage/plugin-search-backend-module-elasticsearch': patch
-'@backstage/plugin-search-backend-module-pg': patch
 ---
 
 Throws `MissingIndexError` when no index of type exist.

plugins/search-backend-module-elasticsearch/src/engines/ElasticSearchSearchEngine.test.ts

@@ -813,7 +813,7 @@ describe('ElasticSearchSearchEngine', () => {
             filters: {},
           }),
       ).rejects.toThrow(
-        'Missing index for unknown__search. This means there are no documents to search through',
+        'Missing index for unknown__search. This means there are no documents to search through.',
       );
     });
   });

plugins/search-backend-module-pg/src/PgSearchEngine/PgSearchEngine.test.ts

@@ -271,21 +271,6 @@ describe('PgSearchEngine', () => {
         limit: 26,
       });
     });
-
-    it('should throws missing index error', async () => {
-      database.transaction.mockImplementation(fn => fn(tx));
-      database.query.mockResolvedValue([]);
-      await expect(
-        async () =>
-          await searchEngine.query({
-            term: 'testTerm',
-            types: ['unknown'],
-            filters: {},
-          }),
-      ).rejects.toThrow(
-        'Missing index for unknown. This means there are no documents to search through',
-      );
-    });
   });
 });
 

plugins/search-backend-module-pg/src/PgSearchEngine/PgSearchEngine.ts

@@ -15,7 +15,6 @@
  */
 import { PluginDatabaseManager } from '@backstage/backend-common';
 import { SearchEngine } from '@backstage/plugin-search-backend-node';
-import { MissingIndexError } from '@backstage/plugin-search-backend-node';
 import {
   SearchQuery,
   IndexableResultSet,
@@ -93,12 +92,6 @@ export class PgSearchEngine implements SearchEngine {
       this.databaseStore.query(tx, pgQuery),
     );
 
-    if (pgQuery?.types && !rows.length) {
-      throw new MissingIndexError(
-        `Missing index for ${pgQuery.types}. This means there are no documents to search through.`,
-      );
-    }
-
     // We requested one result more than the page size to know whether there is
     // another page.
     const { page } = decodePageCursor(query.pageCursor);

plugins/search-backend-node/src/engines/LunrSearchEngine.test.ts

@@ -959,7 +959,7 @@ describe('LunrSearchEngine', () => {
             filters: {},
           }),
       ).rejects.toThrow(
-        'Missing index for unknown. This means there are no documents to search through',
+        "Missing index for unknown. This could be because the index hasn't been created yet or there was a problem during index creation.",
       );
     });
   });

plugins/search-backend-node/src/engines/LunrSearchEngine.ts

@@ -170,7 +170,7 @@ export class LunrSearchEngine implements SearchEngine {
 
     if (documentTypes?.length && !indexKeys.length) {
       throw new MissingIndexError(
-        `Missing index for ${documentTypes?.toString()}. This means there are no documents to search through.`,
+        `Missing index for ${documentTypes?.toString()}. This could be because the index hasn't been created yet or there was a problem during index creation.`,
       );
     }
 

plugins/search-backend/src/service/router.ts

@@ -19,7 +19,7 @@ import Router from 'express-promise-router';
 import { Logger } from 'winston';
 import { z } from 'zod';
 import { errorHandler } from '@backstage/backend-common';
-import { InputError } from '@backstage/errors';
+import { ErrorResponseBody, InputError } from '@backstage/errors';
 import { Config } from '@backstage/config';
 import { JsonObject, JsonValue } from '@backstage/types';
 import { getBearerTokenFromAuthorizationHeader } from '@backstage/plugin-auth-node';
@@ -33,10 +33,7 @@ import {
   IndexableResultSet,
   SearchResultSet,
 } from '@backstage/plugin-search-common';
-import {
-  SearchEngine,
-  MissingIndexError,
-} from '@backstage/plugin-search-backend-node';
+import { SearchEngine } from '@backstage/plugin-search-backend-node';
 import { AuthorizedSearchEngine } from './AuthorizedSearchEngine';
 
 const jsonObjectSchema: z.ZodSchema<JsonObject> = z.lazy(() => {
@@ -134,7 +131,7 @@ export async function createRouter(
     '/query',
     async (
       req: express.Request,
-      res: express.Response<SearchResultSet | string>,
+      res: express.Response<SearchResultSet | ErrorResponseBody>,
     ) => {
       const parseResult = requestSchema.safeParse(req.query);
 
@@ -161,8 +158,9 @@ export async function createRouter(
 
         res.send(filterResultSet(toSearchResults(resultSet)));
       } catch (error) {
-        if (error instanceof MissingIndexError) {
-          res.status(400).json(error.message);
+        if (error.name === 'MissingIndexError') {
+          // re-throw and let the default error handler middleware captures it and serializes it with the right response code on the standard form
+          throw error;
         }
 
         throw new Error(