How to sort files in gulp plugin - sorting

Question

I am writing a gulp plugin which sorts files in stream in order following a comment annotation in each file. I successfully sorted it but I don't know (because maybe I don't understand streams so deeply) how to return ordered stream to gulp pipeline.
Now, I have this and it works.
var through = require('through2');
module.exports = function (options) {
var graph = [],
files = {};
var orderedStream = through.obj();
var sortingStream = through.obj(function (file, enc, cb) {
//file.isNull() and file.isStream() code [...]
//get dependencies [...]
//graph.push(file with dependencies) [...]
files[file.path] = file;
cb();
}, function (cb) {
var ordered = toposort(graph).reverse();
async.eachSeries(ordered, function (filePath, callback) {
orderedStream.write(files[filePath], callback);
}, function () {
cb();
});
});
return {
findOrder : function () {
return sortingStream;
},
sortFiles : function () {
return orderedStream;
}
}
};
Usage of this approach is not as straightforward as I want. You have to use it like this (it works):
gulp.task('default', function () {
var scripts = myPlugin();
return gulp.src('src/**/*js')
.pipe(scripts.findOrder())
.pipe(scripts.sortFiles())
.pipe(concat('build.js'))
.pipe(gulp.dest('dist'));
});
I hope there is a solution which allows to use my plugin as follows:
gulp.task('default', function () {
return gulp.src('src/**/*js')
.pipe(myPlugin())
.pipe(concat('build.js'))
.pipe(gulp.dest('dist'));
});
I experimented a lot but I couldn't come up with any working solution. Any help is appreciated. Thank you.

Answer 1

When you have to first check all the stream then do something with it before returning it, use the flush function in order to provide the stream.
Here is an example:
var through = require('through2');
var files = [];
through.obj(function (chunk, enc, cb) {
//store chunk in the files variable, do not push them onto the stream with this.push
files.push(chunk);
cb();
}, function (cb) {
//here is the flush function, files is now correctly provided
files.sort(); // do what you want with the array
//now you can push whatever you want into the stream
this.push(files[0]);
cb();
});