What are the purposes of vinyl-buffer and gulp-streamify in gulp?

Question

As the documentation says, they both deal with transforming non-stream plugins to stream.

What I try to understand is, if I can use the .pipe() method on something, doesn't it mean it's a stream?

If so, what do I convert to what here?

vinyl-source-stream example:

(from: https://www.npmjs.com/package/vinyl-buffer)

var browserify = require('browserify')
var source = require('vinyl-source-stream')
var buffer = require('vinyl-buffer')
var uglify = require('gulp-uglify')
var size = require('gulp-size')
var gulp = require('gulp')

gulp.task('build', function() {
  var bundler = browserify('./index.js')

  return bundler.pipe()
    .pipe(source('index.js'))
    .pipe(buffer()) // <---------------------- why?
    .pipe(uglify())
    .pipe(size())
    .pipe(gulp.dest('dist/'))
})

gulp-streamify example:

(from: https://www.npmjs.com/package/vinyl-source-stream)

var source = require('vinyl-source-stream')
var streamify = require('gulp-streamify')
var browserify = require('browserify')
var uglify = require('gulp-uglify')
var gulp = require('gulp')

gulp.task('browserify', function() {
  var bundleStream = browserify('index.js').bundle()

  bundleStream
    .pipe(source('index.js'))
    .pipe(streamify(uglify())) // <----------- why?
    .pipe(gulp.dest('./bundle.js'))
})

Answer 1

One semi-useful example is to think about putting out a campfire with a bucket of water. To put out the fire you would want to completely fill up the bucket before dumping it on the fire rather putting a few drops in the bucket and then dumping lots of little drops over time on the fire. This metaphor doesn't capture everything but the big idea is this: you need a FULL bucket of water before you can put out the fire.

That "uglify" plugin works the same way. Imagine some enormous JS file you'd want to compress/uglify.

It will take a little bit of time to load the whole codebase & you definitely wouldn't want to try minifying each line as it comes in, right? Imagine you load a single line, minify it, load another line, minify it, etc etc-- it'd be a mess. You can't stream it (you need a full "bucket" of code before you can uglify it.) To uglify that file properly you'd need to load all that code first before attempting to uglify it.

Since Gulp is a "streaming" build system, you can't use uglify unless you have some mechanism to turn the stream into a buffer (& when it's done emit a stream.) Both tools you mention make this possible.

Here's the flow: STREAM > (BUFFER) > {perform some work on the whole "buffered" file} > STREAM > {other gulp work, etc }

To your specific question, you can use .pipe() because vinyl-buffer/gulp-streamify help "convert" streams to buffers then buffers to streams. They're different approaches to accomplish essentially the same thing.