feat!: remove Cursor#transformStream

NODE-2324

Author: Thomas Reggi

src/cursor/cursor.ts

@@ -1,6 +1,6 @@
 import { emitDeprecatedOptionWarning } from '../utils';
 import { ReadPreference, ReadPreferenceLike } from '../read_preference';
-import { Transform, PassThrough, Readable } from 'stream';
+import { Readable } from 'stream';
 import { deprecate } from 'util';
 import { MongoError, AnyError } from '../error';
 import {
@@ -886,32 +886,9 @@ export class Cursor<
 
   /** Return a modified Readable stream including a possible transform method. */
   stream(options?: CursorStreamOptions): CursorStream {
-    // TODO: replace this method with transformStream in next major release
     return new CursorStream(this, options);
   }
 
-  /**
-   * Return a modified Readable stream that applies a given transform function, if supplied. If none supplied,
-   * returns a stream of unmodified docs.
-   */
-  transformStream(options?: CursorStreamOptions): Transform {
-    const streamOptions: typeof options = options || {};
-    if (typeof streamOptions.transform === 'function') {
-      const stream = new Transform({
-        objectMode: true,
-        transform(chunk, encoding, callback) {
-          if (streamOptions.transform) {
-            this.push(streamOptions.transform(chunk));
-          }
-          callback();
-        }
-      });
-      return this.stream().pipe(stream);
-    }
-
-    return this.stream(options).pipe(new PassThrough({ objectMode: true }));
-  }
-
   /**
    * Execute the explain for the cursor
    *

test/functional/cursor.test.js

@@ -4121,7 +4121,7 @@ describe('Cursor', function () {
         .then(() => collection.insertMany(docs))
         .then(() => {
           cursor = collection.find();
-          return cursor.transformStream(transformParam);
+          return cursor.stream(transformParam);
         })
         .then(stream => {
           stream.on('data', function (doc) {
@@ -4141,7 +4141,7 @@ describe('Cursor', function () {
     });
   };
 
-  it('transformStream should apply the supplied transformation function to each document in the stream', function (done) {
+  it('stream should apply the supplied transformation function to each document in the stream', function (done) {
     const configuration = this.configuration;
     const client = configuration.newClient({ w: 1 }, { poolSize: 1, auto_reconnect: false });
     const expectedDocs = [
@@ -4152,15 +4152,15 @@ describe('Cursor', function () {
     const config = {
       client: client,
       configuration: configuration,
-      collectionName: 'transformStream-test-transform',
+      collectionName: 'stream-test-transform',
       transformFunc: doc => ({ _id: doc._id, b: doc.a.b, c: doc.a.c }),
       expectedSet: new Set(expectedDocs)
     };
 
     testTransformStream(config, done);
   });
 
-  it('transformStream should return a stream of unmodified docs if no transform function applied', function (done) {
+  it('stream should return a stream of unmodified docs if no transform function applied', function (done) {
     const configuration = this.configuration;
     const client = configuration.newClient({ w: 1 }, { poolSize: 1, auto_reconnect: false });
     const expectedDocs = [