Make the QueryTranslator a more integral part of the SearchEngine API

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

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

@@ -18,6 +18,15 @@ import { getVoidLogger } from '@backstage/backend-common';
 import { LunrSearchEngine } from './LunrSearchEngine';
 import { SearchEngine } from '../types';
 
+/**
+ * Just used to test the default translator shipped with LunrSearchEngine.
+ */
+class LunrSearchEngineForTranslatorTests extends LunrSearchEngine {
+  getTranslator() {
+    return this.translator;
+  }
+}
+
 describe('LunrSearchEngine', () => {
   let testLunrSearchEngine: SearchEngine;
 
@@ -27,16 +36,21 @@ describe('LunrSearchEngine', () => {
 
   describe('translator', () => {
     it('query translator invoked', async () => {
-      const translatorSpy = jest.spyOn(testLunrSearchEngine, 'translator');
+      // Given: Set a translator spy on the search engine.
+      const translatorSpy = jest.fn().mockReturnValue({
+        lunrQueryString: '',
+        documentTypes: [],
+      });
+      testLunrSearchEngine.setTranslator(translatorSpy);
 
-      // Translate query and ensure the translator was invoked.
-      await testLunrSearchEngine.translator({
+      // When: querying the search engine
+      testLunrSearchEngine.query({
         term: 'testTerm',
         filters: {},
         pageCursor: '',
       });
 
-      expect(translatorSpy).toHaveBeenCalled();
+      // Then: the translator is invoked with expected args.
       expect(translatorSpy).toHaveBeenCalledWith({
         term: 'testTerm',
         filters: {},
@@ -45,39 +59,54 @@ describe('LunrSearchEngine', () => {
     });
 
     it('should return translated query', async () => {
-      const mockedTranslatedQuery = await testLunrSearchEngine.translator({
+      const inspectableSearchEngine = new LunrSearchEngineForTranslatorTests({
+        logger: getVoidLogger(),
+      });
+      const translatorUnderTest = inspectableSearchEngine.getTranslator();
+
+      const actualTranslatedQuery = translatorUnderTest({
         term: 'testTerm',
         filters: {},
         pageCursor: '',
       });
 
-      expect(mockedTranslatedQuery).toMatchObject({
+      expect(actualTranslatedQuery).toMatchObject({
         documentTypes: ['*'],
         lunrQueryString: '+testTerm',
       });
     });
 
     it('should return translated query with 1 filter', async () => {
-      const mockedTranslatedQuery = await testLunrSearchEngine.translator({
+      const inspectableSearchEngine = new LunrSearchEngineForTranslatorTests({
+        logger: getVoidLogger(),
+      });
+      const translatorUnderTest = inspectableSearchEngine.getTranslator();
+
+      const actualTranslatedQuery = translatorUnderTest({
         term: 'testTerm',
         filters: { kind: 'testKind' },
         pageCursor: '',
       });
 
-      expect(mockedTranslatedQuery).toMatchObject({
+      expect(actualTranslatedQuery).toMatchObject({
         documentTypes: ['*'],
         lunrQueryString: '+testTerm +kind:testKind',
       });
     });
 
     it('should return translated query with multiple filters', async () => {
-      const mockedTranslatedQuery = await testLunrSearchEngine.translator({
+      const inspectableSearchEngine = new LunrSearchEngineForTranslatorTests({
+        logger: getVoidLogger(),
+      });
+      const translatorUnderTest = inspectableSearchEngine.getTranslator();
+
+      const actualTranslatedQuery = translatorUnderTest({
         term: 'testTerm',
         filters: { kind: 'testKind', namespace: 'testNameSpace' },
         pageCursor: '',
       });
 
-      expect(mockedTranslatedQuery).toMatchObject({
+      expect(actualTranslatedQuery).toMatchObject({
         documentTypes: ['*'],
         lunrQueryString: '+testTerm +kind:testKind +namespace:testNameSpace',
       });

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

@@ -33,6 +33,8 @@ type LunrResultEnvelope = {
   type: string;
 };
 
+type LunrQueryTranslator = (query: SearchQuery) => ConcreteLunrQuery;
+
 export class LunrSearchEngine implements SearchEngine {
   protected lunrIndices: Record<string, lunr.Index> = {};
   protected docStore: Record<string, IndexableDocument>;
@@ -43,7 +45,7 @@ export class LunrSearchEngine implements SearchEngine {
     this.docStore = {};
   }
 
-  translator: QueryTranslator = ({
+  protected translator: QueryTranslator = ({
     term,
     filters,
     types,
@@ -82,6 +84,10 @@ export class LunrSearchEngine implements SearchEngine {
     };
   };
 
+  setTranslator(translator: LunrQueryTranslator) {
+    this.translator = translator;
+  }
+
   index(type: string, documents: IndexableDocument[]): void {
     const lunrBuilder = new lunr.Builder();
     // Make this lunr index aware of all relevant fields.

plugins/search-backend-node/src/types.ts

@@ -59,7 +59,18 @@ export type QueryTranslator = (query: SearchQuery) => unknown;
  * concrete, search engine-specific queries.
  */
 export interface SearchEngine {
-  translator: QueryTranslator;
+  /**
+   * Override the default translator provided by the SearchEngine.
+   */
+  setTranslator(translator: QueryTranslator): void;
+
+  /**
+   * Add the given documents to the SearchEngine index of the given type.
+   */
   index(type: string, documents: IndexableDocument[]): void;
+
+  /**
+   * Perform a search query against the SearchEngine.
+   */
   query(query: SearchQuery): Promise<SearchResultSet>;
 }