assetgraph

AssetGraph

AssetGraph is an extensible, node.js <http://nodejs.org/>_-based framework for manipulating and optimizing web pages and web applications. It's the core of the third generation of the production builder tool we are using at One.com for some of our web apps. It's in a working state, but as indicated by the pre-1.0.0 version number, still likely to undergo changes.

Check out the slides from a presentation of AssetGraph <http://gofish.dk/assetgraph.pdf>_ held at the Öresund JavaScript Meetup <http://www.meetup.com/The-Oresund-JavaScript-Meetup/>_ on June 16th, 2011.

The complete AssetGraph-based build system mentioned in the slides can be found here <https://github.com/One-com/assetgraph-builder>_.

Features

• Build an asset graph programmatically or load it from disk or a remote server via http.
• Find explicit dependencies between JavaScript and CSS roll them out as <script> and <link rel='stylesheet'> tags in your HTML. For now only the ExtJS 4 syntax and a homegrown one.include syntax are supported, but the parsing phase can be adapted to almost any syntax. More script loaders will be added later.
• Bundle and inline CSS and JavaScript.
• Create a cache manifest with references to all the assets your web app needs to be usable offline.
• Move all CSS, JavaScript, image assets etc. to a static dir and rename them to md5.extension so the web server can be configured to set a far-future Cache-Control.
• Help getting your static assets on a CDN by allowing you to easily rewrite all references to them.
• Use Graphviz to visualize your dependencies at any step.
• Using the separate assetgraph-sprite transform <https://github.com/One-com/assetgraph-sprite>_: Optimize CSS background images by creating sprite images. The spriting is guided by a set of custom CSS properties with a -one-sprite prefix.

The observation that inspired the project is that most of the above optimizations are easily expressed in terms of graph manipulations, where the nodes are the assets (HTML, CSS, images, JavaScript...) and the edges are the relations between them, e.g. anchor tags, image tags, favorite icons, css background-image properties and so on.

AssetGraph provides a basic data model that allows you to populate, query, and manipulate the graph at a high level of abstraction. Additionally, each individual asset can be inspected and massaged using a relevant API: DOM for HTML (using jsdom <https://github.com/tmpvar/jsdom>), CSSOM for CSS (using NV's CSSOM module <https://github.com/NV/CSSOM>), and an abstract syntax tree for JavaScript (powered by UglifyJS <https://github.com/mishoo/UglifyJS/>_' parser).

Installation

Make sure you have node.js and npm <http://npmjs.org/>_ installed, then run::

$ npm install assetgraph

API documentation

A work in progress. Look here <http://gofish.dk/assetgraph/api.html>_.

Querying the graph

AssetGraph supports a flexible syntax for finding assets and relations in a populated graph using the findAssets and findRelations methods. Both methods take a query object as the first argument. Below are some basic examples.

Get an array containing all assets in the graph::

var allAssets = assetGraph.findAssets();

Find assets by type::

var htmlAssets = assetGraph.findAssets({type: 'Html'});

Find assets by matching a regular expression against the url::

var localImageAssets = assetGraph.findAssets({url: /^file:.*\.(?:png|gif|jpg)$/});

Find assets by predicate function::

var orphanedJavaScriptAssets = assetGraph.findAssets(function (asset) {
    return asset.type === 'JavaScript' && assetGraph.findRelations({to: asset}).length === 0;
});

Find all HtmlScript (

var allHtmlScriptRelations = assetGraph.findRelations({type: 'HtmlScript'});

Query objects have "and" semantics, so all conditions must be met for a multi-criteria query to match::

var textBasedAssetsOnGoogleCom = assetGraph.findAssets({
    isText: true,
    url: /^https?:\/\/(?:www\.)google\.com\//
});

Find assets by existence of incoming relations (experimental feature)::

var importedCssAssets = assetGraph.findAssets({type: 'Css', incoming: {type: 'CssImport'}})

Relation queries can contain nested asset queries when querying the to and from properties.

Find all HtmlAnchor () relations pointing at local images::

assetGraph.findRelations({
    type: 'HtmlAnchor',
    to: {isImage: true, url: /^file:/}
});

Transforms and workflows

AssetGraph comes with a collection of premade "transforms" that you can use as high level building blocks when putting together your build procedure. Most transforms work on a set of assets or relations and usually accept a query object so they can be scoped to work on only a specific subset of the graph.

Usually you'll start by loading some initial assets from disc or via http using the loadAssets transform, then get the related assets added using the populate transform, then do the actual processing. Eventually you'll probably write the resulting assets back to disc.

Thus the skeleton looks something like this::

var AssetGraph = require('assetgraph'),
    transforms = AssetGraph.transforms;

new AssetGraph({root: '/the/root/directory/'}).queue(
    transforms.loadAssets('*.html'), // Load all Html assets in the root dir
    transforms.populate({followRelations: {type: 'HtmlAnchor'}}), // Follow <a href=...>
    // More work...
    transforms.writeAssetsToDisc({type: 'Html'}) // Overwrite existing files
).run(finishedCallback);

In the following sections the built-in transforms are documented individually:

transforms.addCacheManifest([queryObj])

Add a CacheManifest asset to each Html asset in the graph (or to all Html assets matched by queryObj if provided). The cache manifests will contain relations to all assets reachable by traversing the graph through relations other than HtmlAnchor.

transforms.bundleAssets({type: 'Css'|'JavaScript', incoming: {type: ...}}[, strategyName])

Bundle Css or JavaScript assets. At the very minimum the query object must specify both the type of asset to bundle and the type of the including relations (HtmlStyle or HtmlScript), but can include additional criteria.

The strategyName (string) parameter can be either:

oneBundlePerIncludingAsset (the default) Each unique asset pointing to one or more of the assets being bundled will get its own bundle. This can lead to duplication if eg. several Html assets point to the same sets of assets, but guarantees that the number of http requests is kept low.

sharedBundles Create as many bundles as needed, optimizing for combined byte size of the bundles rather than http requests. Warning: Not as well tested as oneBundlePerIncludingAsset.

Note that a conditional comment within an Html asset conveniently counts as a separate including asset, so in the below example ie.css and all.css won't be bundled together:

<![if IE]><link rel='stylesheet' href='ie.css'><![endif]-->
<link rel='stylesheet' href='all.css'>

The created bundles will be placed at the root of the asset graph with names derived from their unique id (for example file://root/of/graph/124.css) and will replace the original assets.

transforms.compileCoffeeScriptToJavaScript([queryObj])

Finds all CoffeeScript assets in the graph (or those specified by queryObj), compiles them to JavaScript assets and replaces the originals.

transforms.compressJavaScript([queryObj[, compressorName[, compressorOptions]]])

Compresses all JavaScript assets in the graph (or those specified by queryObj).

The compressorName (string) parameter can be either:

uglify (the default and the fastest) The excellent UglifyJS <https://github.com/mishoo/UglifyJS>_ compressor. If provided, the compressorOptions object will be passed to UglifyJS' ast_squeeze command.

yuicompressor Yahoo's YUICompressor though Tim-Smart's node-yuicompressor module <https://github.com/Tim-Smart/node-yui-compressor>_. If provided, the compressorOptions object will be passed as the second argument to require('yui-compressor').compile.

closurecompiler Google's Closure Compiler through Tim-Smart's node-closure module <https://github.com/Tim-Smart/node-closure>_. If provided, the compressorOptions object will be passed as the second argument to require('closure-compiler').compile.

transforms.convertCssImportsToHtmlStyles([queryObj])

Finds all Html assets in the graph (or those specified by queryObj), finds all CssImport relations (@import url(...)) in inline and external CSS and converts them to HtmlStyle relations directly from the Html document.

Effectively the inverse of transforms.convertHtmlStylesToInlineCssImports.

Example::

<style type='text/css'>
    @import url(print.css) print;
    @import url(foo.css);
    body {color: red;}
</style>

is turned into::

body {color: red;}

transforms.convertHtmlStylesToInlineCssImports([queryObj])

Finds all Html assets in the graph (or those specified by queryObj), finds all outgoing, non-inline HtmlStyle relations (<link rel='stylesheet' href='...'>) and turns them into groups of CssImport relations (@import url(...)) in inline stylesheets. A maximum of 31 CssImports will be created per inline stylesheet.

Example::

 <link rel='stylesheet' href='foo.css'>
 <link rel='stylesheet' href='bar.css'>

is turned into::

 <style type='text/css'>
     @import url(foo.css);
     @import url(bar.css);
 </style>

This is a workaround for the limit of 31 stylesheets in Internet Explorer <= 8 <http://social.msdn.microsoft.com/Forums/en-US/iewebdevelopment/thread/ad1b6e88-bbfa-4cc4-9e95-3889b82a7c1d/>_. This transform allows you to have up to 31*31 stylesheets in the development version of your HTML and still have it work in older Internet Explorer versions.

transforms.drawGraph(fileName)

Uses the Graphviz dot command through node-graphviz <https://github.com/glejeune/node-graphviz>_ to render the current contents of the graph and writes the result to fileName. The image format is automatically derived from the extension and can be any of these <http://www.graphviz.org/doc/info/output.html>_. Using .svg is recommended.

Requires Graphviz to be installed, sudo apt-get install graphviz on Debian/Ubuntu.

transforms.executeJavaScriptInOrder(queryObj[, context])

Experimental: For each asset matched by (or those matched by queryObj), find all reachable JavaScript assets and execute them in order.

If the context parameter is specified, it will be used as the execution context <http://nodejs.org/docs/latest/api/vm.html#vm.runInContext>_. Otherwise a new context will be created using vm.createContext <http://nodejs.org/docs/latest/api/vm.html#vm.createContext>.

transforms.externalizeRelations([queryObj])

Finds all inline relations in the graph (or those matched by queryObj) and makes them external. The file names will be derived from the unique ids of the assets.

For example::

 <script>foo = 'bar';</script>
 <style type='text/css'>body {color: maroon;}</style>

could be turned into::

 <script src='4.js'></script>
 <link rel='stylesheet' href='5.css'>

transforms.flattenStaticIncludes(queryObj)

Finds all Html assets in the graph (or those matched by queryObj), finds all JavaScript and Css assets reachable through HtmlScript, HtmlStyle, JavaScriptOneInclude, and JavaScriptExtJsRequire relations and rolls them out as plain HtmlScript (<script src='...'>) and HtmlStyle (<link rel='stylesheet' href='...'>) relations.

If your project uses deeply nested one.include statements, this transform allows you to create a "development version" that works in a browser. Refer to the buildDevelopment script from AssetGraph-builder <https://github.com/One-com/assetgraph-builder/blob/master/bin/buildDevelopment>_.

For example::

<head></head>
<body>
    <script>one.include('foo.js');</script>
</body>

where foo.js contains::

one.include('bar.js');
one.include('quux.css');
var blah = 'baz';
...

is turned into::

<head>
    <link rel='stylesheet' href='quux.css'>
</head>
<script src='bar.js'></script>
<script src='foo.js'></script>

transforms.inlineCssImagesWithLegacyFallback([queryObj[, sizeThreshold]])

Finds all Html assets in the graph (or those matched by queryObj), finds all directly reachable Css assets, and converts the outgoing CssImage relations (background-image etc.) to data: urls, subject to these criteria:

1. If sizeThreshold is specified, images with a greater byte size won't be inlined.

2. To avoid duplication, images referenced by more than one CssImage relation won't be inlined.

If any image is inlined an Internet Explorer-only version of the stylesheet will be created and referenced from the Html asset in a conditional comment.

For example::

assetGraph.runTransform(transforms.inlineCssImagesWithLegacyFallback(), cb);

where assetGraph contains an Html asset with this fragment::

<link rel='stylesheet' href='foo.css'>

and foo.css contains::

body {background-image: url(small.png);}

will be turned into::

<!--[if IE]><link rel="stylesheet" href="foo.css"><![endif]-->
<!--[if !IE]>--><link rel="stylesheet" href="1234.css"><!--<![endif]-->

where 1234.css is a copy of the original foo.css with the images inlined as data: urls::

body {background-image: url(data;image/png;base64,iVBORw0KGgoAAAANSUhE...)}

The file name 1234.css is just an example. The actual asset file name will be derived from the unique id of the copy and be placed at the root of the assetgraph.

transforms.inlineRelations([queryObj])

Inlines all relations in the graph (or those matched by queryObj). Only works on relation types that support inlining, for example HtmlScript, HtmlStyle, and CssImage.

Example::

assetGraph.runTransform(transforms.inlineRelations({type: ['HtmlStyle', 'CssImage']}));

where assetGraph contains an Html asset with this fragment::

<link rel='stylesheet' href='foo.css'>

and foo.css contains::

body {background-image: url(small.png);}

will be turned into::

<style type='text/css'>body {background-image: url(data;image/png;base64,iVBORw0KGgoAAAANSUhE...)}</style>

Note that foo.css and the CssImage will still be modelled as separate assets after being inlined, so they can be manipulated the same way as when they were external.

transforms.loadAssets(fileName|wildcard|url|Asset[, ...])

Add new assets to the graph and make sure they are loaded. Several syntaxes are supported, for example::

transforms.loadAssets('a.html', 'b.css') // Relative to assetGraph.root
transforms.loadAssets(new AssetGraph.assets.JavaScript({
    url: "http://example.com/index.html",
    text: "var foo = bar;" // The source is specified, won't be loaded
});

file:// urls support wildcard expansion::

transforms.loadAssets('file:///foo/bar/*.html') // Wildcard expansion
transforms.loadAssets('*.html') // assetGraph.root must be file://...

transforms.mergeIdenticalAssets([queryObj])

Compute the MD5 sum of every asset in the graph (or those specified by queryObj and remove duplicates. The relations pointing at the removed assets are updated to point at the copy that is kept.

For example::

assetGraph.runTransform(transforms.mergeIdenticalAssets(), cb);

where assetGraph contains an Html asset with this fragment::

<head>
    <style type='text/css'>body {background-image: url(foo.png);}</style>
</head>
<body>
    <img src='bar.png'>
</body>

will be turned into the following if foo.png and bar.png are identical::

<head>
    <style type='text/css'>body {background-image: url(foo.png);}</style>
</head>
<body>
    <img src='foo.png'>
</body>

and the bar.png asset will be removed from the graph.

transforms.minifyAssets([queryObj])

Minify all assets in the graph, or those specified by queryObj. Only has an effect for asset types that support minification, and what actually happens also varies:

Html and Xml: Pure-whitespace text nodes are removed immediately.

Json, JavaScript, and Css: The asset gets marked as minified (isPretty is set to false), which doesn't affect the in-memory representation (asset.parseTree), but is honored when the asset is serialized. For JavaScript this only governs the amount of whitespace (UglifyJS' beautify parameter); for how to apply variable renaming and other compression techniques see transforms.compressJavaScript.

transforms.moveAssets

transforms.moveAssetsInOrder

transforms.moveAssetsToNewRoot

transforms.parallel

transforms.populate

transforms.postProcessBackgroundImages

transforms.prettyPrintAssets(queryObj)

The inverse of transforms.minifyAssets.

transforms.removeAssets

transforms.removeRelations

transforms.setAssetContentType

transforms.setAssetEncoding

transforms.setAssetExtension

transforms.setHtmlImageDimensions

transforms.startOverIfAssetSourceFilesChange

transforms.stats

transforms.writeAssetsToDisc

transforms.writeAssetsToStdout

License

AssetGraph is licensed under a standard 3-clause BSD license -- see the LICENSE-file for details.

Changelog

v0.3.8

• Release 0.3.8. (Andreas Lind Petersen)
• Changed glob dependency to ~2.0.7 (2.0.7 disappeared from the npm repo?). (Andreas Lind Petersen)
• Added transforms.setHtmlImageDimensions. (Andreas Lind Petersen)
• transforms.inlineCssImagesWithLegacyFallback: Default to non-inline Html assets to avoid processing HtmlStyle relations in existing conditional comments. (Andreas Lind Petersen)
• Now working on 0.3.8. (Andreas Lind Petersen)