A small example of a "Vinyl adapter" that replaces `gulp.src`. Demonstrates how to create a stream for a "fake" (in-memory only) file.

gulpfile.js

import gulp from 'gulp';
import Vinyl from 'vinyl';
import vinylAdapter from './vinyl-adapter';

gulp.task('build', () => {
  const file = new Vinyl({
    path: 'hello.js',
    contents: Buffer.from(`console.log('👋');`)
  });

  // Output hello.js to the dist directory.
  return vinylAdapter(file).pipe(gulp.dest('dist'));
});

vinyl-adapter.js

import { PassThrough } from 'node:stream';
import Vinyl from 'vinyl';

/**
 * Create a stream from a Vinyl file.
 *
 * Typically, `gulp.src` is used to create a stream of Vinyl files.
 * Use this function when you need to work backwards i.e. you already
 * have a reference to a Vinyl file and want to start streaming it.
 */
export default function(file) {
  if (!Vinyl.isVinyl(file)) {
    throw new Error('The specified file is not a Vinyl.');
  }

  const stream = new PassThrough({ objectMode: true });
  stream.end(file);
  return stream;
}

Some discussion about "vinyl adapters" here.