Startup Technology Consultant and UI/UX Expert

Learn more about gulp.js, the streaming build system

Introduction

Gulp-data proposes a common API for attaching data to the file object for other plugins to consume. With gulp-data you can generate a data object from a variety of sources: json, front-matter, database, anything... and set it to the file object for other plugins to consume.

Many plugins, such as gulp-swig or gulp-jade allow for JSON data to be passed via their respective options parameter. However, frequently what you want is the ability to dynamically set the data based off the file name or some other attribute of the file. Without using another plugin, this becomes problematic - as the number of ways of getting at data (via JSON files, front-matter, data bases, promises, etc) increases, the more plugin authors have to update their APIs to support these sources. The gulp-data plugin aims to standardize a method that is generic enough to encapsulate these data sources into a single data property attached to the file object. It's really up to you as to where your data comes from, a JSON file, from a front-matter section of the file, or even a database, gulp-data doesn't really care.

However, for this to be effective, I'm asking plugin devs that receive data through the options parameter to make a small change to additionally accept this data through the file.data property. (See below)

Important Update

Thanks to the help of @izaakschroeder we've reached version 1.0 (now 1.0.1). Some important changes have been added, primarily support for promises, and error handling. The examples below have been updated to reflect these changes.

Usage

First, install gulp-data as a development dependency:

npm install --save-dev gulp-data

Then, add it to your gulpfile.js:

var gulp = require('gulp')
var swig = require('gulp-swig')
var data = require('gulp-data')
var fm = require('front-matter')
var path = require('path')
var MongoClient = require('mongodb').MongoClient
var fs = require('fs')

/*
  Get data via JSON file, keyed on filename.
*/
gulp.task('json-test', function() {
  return gulp
    .src('./examples/test1.html')
    .pipe(
      data(function(file) {
        return JSON.parse(
          fs.readFileSync('./examples/' + path.basename(file.path) + '.json')
        )
      })
    )
    .pipe(swig())
    .pipe(gulp.dest('build'))
})

/*
  Get data via front matter
*/
gulp.task('fm-test', function() {
  return gulp
    .src('./examples/test2.html')
    .pipe(
      data(function(file) {
        var content = fm(String(file.contents))
        file.contents = new Buffer(content.body)
        return content.attributes
      })
    )
    .pipe(swig())
    .pipe(gulp.dest('build'))
})

/*
  Get data via database, keyed on filename.
*/
gulp.task('db-test', function() {
  return gulp
    .src('./examples/test3.html')
    .pipe(
      data(function(file, cb) {
        MongoClient.connect(
          'mongodb://127.0.0.1:27017/gulp-data-test',
          function(err, db) {
            if (err) return cb(err)
            cb(
              undefined,
              db
                .collection('file-data-test')
                .findOne({ filename: path.basename(file.path) })
            )
          }
        )
      })
    )
    .pipe(swig())
    .pipe(gulp.dest('build'))
})

API

data(dataFunction)

dataFunction

Type: Function

Define a function that returns a data object via a callback function. Could return JSON from a file, or an object returned from a database.

You can return the data object:

data(function(file) {
  return { foo: file.path }
})

You can return a promise:

data(function(file) {
  return promise
})

You can feed a result object through the callback:

data(function(file, callback) {
  return callback(undefined, { foo: 'bar' })
})

You can feed a promise object through the callback:

data(function(file, callback) {
  return callback(undefined, promise)
})

You can throw an error:

data(function(file) {
  throw new Error('my-error')
})

You can raise an error via the callback:

data(function(file, callback) {
  return callback('error')
})

Note to gulp plugin authors

If your plugin needs a data object, one that normally gets passed in via your options parameter, I'm asking if you could please update the plugin to accept data from the file.data property. Here's how you can do it:

gulp-swig usually accepts data via its options.data parameter, but with a small change, it checks to see if there's a file.data property and if so, merges it into the data object.

var data = opts.data || {}
if (file.data) {
  data = _.extend(file.data, data)
  // or just data = file.data if you don't care to merge. Up to you.
}

Author

@colynb

Contributors

Libraries Using `gulp-data`

Gulp Starter (a delicious blend of tasks and build tools)

License

MIT License

gulp-data