Simplify base classes by using stream _construct methods

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

.changeset/search-om-manniskan-ginge.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-search-backend-node': patch
+---
+
+Updated indexer and decorator base classes to take advantage of features introduced in Node.js v16; be sure you are running a [supported version of Node.js](https://backstage.io/docs/releases/v1.8.0#node-16-and-18).

plugins/search-backend-node/src/indexing/BatchSearchEngineIndexer.ts

@@ -34,26 +34,10 @@ export type BatchSearchEngineOptions = {
 export abstract class BatchSearchEngineIndexer extends Writable {
   private batchSize: number;
   private currentBatch: IndexableDocument[] = [];
-  private initialized: Promise<undefined | Error>;
 
   constructor(options: BatchSearchEngineOptions) {
     super({ objectMode: true });
     this.batchSize = options.batchSize;
-
-    // @todo Once node v15 is minimum, convert to _construct implementation.
-    this.initialized = new Promise(done => {
-      // Necessary to allow concrete implementation classes to construct
-      // themselves before calling their initialize() methods.
-      setImmediate(async () => {
-        try {
-          await this.initialize();
-          done(undefined);
-        } catch (e) {
-          assertError(e);
-          done(e);
-        }
-      });
-    });
   }
 
   /**
@@ -73,6 +57,20 @@ export abstract class BatchSearchEngineIndexer extends Writable {
    */
   public abstract finalize(): Promise<void>;
 
+  /**
+   * Encapsulates initialization logic.
+   * @internal
+   */
+  async _construct(done: (error?: Error | null | undefined) => void) {
+    try {
+      await this.initialize();
+      done();
+    } catch (e) {
+      assertError(e);
+      done(e);
+    }
+  }
+
   /**
    * Encapsulates batch stream write logic.
    * @internal
@@ -82,13 +80,6 @@ export abstract class BatchSearchEngineIndexer extends Writable {
     _e: any,
     done: (error?: Error | null) => void,
   ) {
-    // Wait for init before proceeding. Throw error if initialization failed.
-    const maybeError = await this.initialized;
-    if (maybeError) {
-      done(maybeError);
-      return;
-    }
-
     this.currentBatch.push(doc);
     if (this.currentBatch.length < this.batchSize) {
       done();
@@ -111,12 +102,6 @@ export abstract class BatchSearchEngineIndexer extends Writable {
    */
   async _final(done: (error?: Error | null) => void) {
     try {
-      const maybeError = await this.initialized;
-      if (maybeError) {
-        done(maybeError);
-        return;
-      }
-
       // Index any remaining documents.
       if (this.currentBatch.length) {
         await this.index(this.currentBatch);

plugins/search-backend-node/src/indexing/DecoratorBase.ts

@@ -24,25 +24,8 @@ import { Transform } from 'stream';
  * @public
  */
 export abstract class DecoratorBase extends Transform {
-  private initialized: Promise<undefined | Error>;
-
   constructor() {
     super({ objectMode: true });
-
-    // @todo Once node v15 is minimum, convert to _construct implementation.
-    this.initialized = new Promise(done => {
-      // Necessary to allow concrete implementation classes to construct
-      // themselves before calling their initialize() methods.
-      setImmediate(async () => {
-        try {
-          await this.initialize();
-          done(undefined);
-        } catch (e) {
-          assertError(e);
-          done(e);
-        }
-      });
-    });
   }
 
   /**
@@ -68,6 +51,20 @@ export abstract class DecoratorBase extends Transform {
    */
   public abstract finalize(): Promise<void>;
 
+  /**
+   * Encapsulates initialization logic.
+   * @internal
+   */
+  async _construct(done: (error?: Error | null | undefined) => void) {
+    try {
+      await this.initialize();
+      done();
+    } catch (e) {
+      assertError(e);
+      done(e);
+    }
+  }
+
   /**
    * Encapsulates simple transform stream logic.
    * @internal
@@ -77,13 +74,6 @@ export abstract class DecoratorBase extends Transform {
     _: any,
     done: (error?: Error | null) => void,
   ) {
-    // Wait for init before proceeding. Throw error if initialization failed.
-    const maybeError = await this.initialized;
-    if (maybeError) {
-      done(maybeError);
-      return;
-    }
-
     try {
       const decorated = await this.decorate(document);