Incorrect handling of binary content from stdout

[Glebka]

Hi.

gulp-exec plugin corrupts binary data that come from stdout. See example gulpfile.js below.

gulp.task("extractAlpha", function() {
  var options = {
    continueOnError: false,
    pipeStdout: true,
    encoding: 'binary'
  };
  return gulp
    .src("./*.png")
    .pipe(
        exec(
          "convert <%= file.path %> -alpha extract -",
          options
        )
      )    
    .pipe(gulp.dest('out/'));    
});

Here you can see extractAlpha task that uses convert CLI tool from ImageMagick distribution. It extracts alpha channel as a separate image and outputs the result to the stdout.
When I run this task I get corrupted image in the output folder. Note, that I've specified encoding: 'binary' option for exec but it doesn't help.

The root cause of the issue is here:

gulp-exec/index.js

Line 38 in 8f934d9

file.contents = new Buffer(stdout); // FRAGILE: if it wasn't a buffer it is now

Providing an encoding when creating a Buffer should fix the issue.

Will create PR for this soon.

This issue occurs on:
Windows 8.1, NodeJS v8.11.2

[robrich]

Thanks for the PR. It also sounds like you've outgrown gulp-exec as gulp spends a lot of time loading the file contents and piping things around which you're not using. You may want to swap to:

const exec = require('child_process').exec;
const glob = require('glob');
const promisify = require('util').promisify;

const execAsPromise = promisify(exec);

gulp.task("extractAlpha", function(cb) {
  glob("./*.png", function (err, files) {
    let promises = files.map(file => execAsPromise(`convert ${file} -alpha extract > out/${file}`));
    Promise.all(promises).then(cb);
  });
});

[Glebka]

Thanks for advice :) I am new to gulp and just playing with it to understand how it works.
Well, actually I am trying to modify the code of that guy because he uses make for generating shapes from png images. Just trying to replace make with gulp because I am too lazy to install make on Windows :)