Assemble collections example

a.hbs

---
tags:
- a
- b
- c
---

Make a few pages like this, with the same or different tags in the front-matter.

assemblefile.js

var assemble = require('assemble');
var through = require('through2');
var extname = require('gulp-extname');
var File = require('vinyl');

/**
 * Create a new template type for caching and loading
 * "index" templates
 */

assemble.create('index', 'indices', {isRenderable: true});
assemble.indices('templates/indices/*.hbs');

/**
 * Task with:
 *  - 'tags' plugin, which currently only will generate a list (index) of tags from front-matter of all files in the task
 *  - 'extname' plugin for renaming extensions to 'html'
 */

assemble.task('default', function () {
  assemble.src('templates/*.hbs')
    .pipe(tags('basic'))
    .pipe(extname())
    .pipe(assemble.dest('result/'));
});

/**
 * 'tags' plugin
 *
 *   - in the main function, we push the file into a `files`
 *     array, then we push the file back into the stream
 *   - in the flush function we take the `files` array that we built up,
 *     then we create a new vinyl file using the template defined by the
 *     user in the task. in this case, the template name is `basic`
 */

function tags(template) {
  var files = [];
  return through.obj(function (file, enc, cb) {
    files.push(file);
    this.push(file);
    cb();
  }, function (cb) {
    var stream = this;
    var arr = [];

    // here, we add the tags from front-matter to an array.
    // we could make this more useful by also adding the dest
    // path of the file and other info.
    files.forEach(function (file) {
      arr = arr.concat(file.data.tags);
    });

    var tmpl = assemble.views.indices[template];
    tmpl.data.tags = arr;

    assemble.render(tmpl, function (err, content) {
      if (err) console.log(err);
      var file = new File({path : 'index.html'});
      // `data` needed for assemble
      file.data = {};
      file.contents = new Buffer(content);
      stream.push(file);
      cb();
    });
  });
}

basic.hbs

{{#tags}}
<span>{{.}}</span>
{{/tags}}