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Keynote: The Asset Pipeline and Our Postmodern Hybrid JavaScript Future
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Keynote: The Asset Pipeline and Our Postmodern Hybrid JavaScript Future
by David Heinemeier HanssonIn this keynote presentation, titled "The Asset Pipeline and Our Postmodern Hybrid JavaScript Future," delivered by David Heinemeier Hansson at RailsConf 2011, the focus is primarily on the new features introduced in Rails 3.1, particularly the Asset Pipeline. This feature is designed to enhance how developers manage assets like JavaScript, CSS, and images within their Rails applications, addressing long-standing frustrations with asset organization.
Key points discussed in the presentation include:
- The Motivation for the Asset Pipeline: Hansson emphasizes that the motivation for improvements in Rails often stems from identifying pain points in development. He highlights the clutter that arises from unsystematic organization of JavaScript files, comparing it to a messy junk drawer that becomes hard to work with over time.
- Grouping and Organization: The presentation emphasizes the importance of organizing files in logical groupings rather than clustering them chaotically. Hansson proposes the idea of a rule where directories should ideally house no more than 13 files, reinforcing a tidy organizational structure.
- Improvements over Previous Methods: With Rails 3.1, the Asset Pipeline replaces the earlier approach that involved a single large JavaScript file with a more structured method of organizing assets into three main categories: application-specific assets, library assets, and vendor assets, which significantly reduces clutter.
- Centralized Dependency Management: The presentation illustrates how the Asset Pipeline allows for better dependency management using tools like Bundler, enabling smooth handling of JavaScript and stylesheets without manual intervention.
- Introduction of CoffeeScript: Hansson concludes by discussing CoffeeScript, a more user-friendly syntax for JavaScript that allows for cleaner and more maintainable code, ultimately enhancing the developer experience.
In conclusion, Hansson asserts that the Asset Pipeline not only provides a much-needed solution to asset organization challenges but also encourages developers to create cleaner and more enjoyable coding experiences. The separation and management of assets along with the introduction of CoffeeScript signal a significant step towards a more cohesive and efficient Rails development environment.
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Alright, so Rails 3.1 is just around the corner, and it includes a lot of wonderful features.
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I am going to talk mainly about one of those wonderful features today, but I'm sure we'll have plenty of information about the rest.
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This talk is entitled "The Asset Pipeline and Our Postmodern Hybrid JavaScript Future."
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Let's start with the first part, the Asset Pipeline, which is by far my favorite new element in Rails 3.1.
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I think it's going to have a huge impact on how we all create Rails applications moving forward.
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But before we go into the mechanics of how it works, I want to focus a little bit on the origins of how this came about.
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All of the things that I try to work on in Rails start out as problems; something that's just a nagging sense that this stuff could be better.
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There's a direct pain, something that jumps out at me when I'm looking at a Rails code base and thinking, 'This is really not good enough.' We have to do better here.
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A lot of the time, that pain is actually visual—I'll be looking at a piece of code and it just offends me.
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There's something here that's supposed to be simpler and cleaner; why is this a mess?
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We've been going through this cycle over and over again with Rails, and that's how we usually release new versions.
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We reduce pain by taking it out and leaving it with something more pleasurable. I think that's a good cycle to be in when you're trying to design a framework.
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It's essential to focus on the problems and the pain points, because then you know when you're done.
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It’s easy to get carried away while programming as a framework builder, and before you know it, you have much more than that original pain.
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We try really hard not to have too much clutter. The features that go into a new version of Rails arise from someone being personally annoyed about the old way.
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One of the things that I've been annoyed about for a long time is this mess. This is a directory in Basecamp containing all the JavaScript files in one big lump named 'JavaScript'.
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Seeing this image, I thought, 'This is terrible! Why are all these files in one big lump?'
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When you dive into it, it offends you even more; look at these files, for example, calendar date.js, calendar date format, calendar date select.
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This is a unit of work that should be grouped together, but the only way we're grouping it is by underscores.
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That's a pretty poor form of grouping.
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Not only that, but it is at a completely different level of abstraction than, say, fancy Zoom, which is another library just dumped into the same directory.
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I have code that I wrote right next to code that somebody else wrote. That doesn't feel right.
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These elements might both be library code, but they feel like they should be separate.
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It gets worse when you look at other elements, for example, milestones.js. This is JavaScript that belongs to a single controller.
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We're mixing levels of abstraction that have nothing to do with each other; it's just a big cluster.
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It's a junk drawer; it's not that junk drawers aren’t useful, they sometimes have useful tools.
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If you have to go into a junk drawer to get something, that's not a great way to start the day.
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You want the measuring tape to be together with other things that have to do with measuring and cutting, not mixed with rubber bands or pencils.
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I've found a general rule: if you have more than 13 things together, it's not good.
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When looking at files, methods, or directories, as soon as we get above that, it feels messy. When it feels messy, you need to push back.
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Folders have this problem of the boiling frog—you slowly get boiled.
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No folders start out with 20 files. They start out with two files; you add one more, and then you have three.
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Then you add a few more, and suddenly you have 15. You think, 'How did I get here?'.
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I felt this project was nice and clean at the start, and then something happened. It wasn't clean anymore.
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So how do we combat this? How can we enforce this metric?
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What if we just had folders that could only hold 13 files? You couldn't add another file to it.
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It sounds arbitrary, which is often how laws come to be—arbitrary restrictions that don’t explain their reasoning.
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You want a rule in place to ensure you develop a clean application, but also want justification for why the rule exists.
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We had a similar problem with REST, applied to controllers. Controllers had a tendency to accumulate over 13 methods.
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Just adding one more method doesn’t feel bad, but before you know it, you have too many.
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So we put a natural restriction of six.
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If you go over six methods, it feels wrong because you’re somehow breaking the conventions established.
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We should think about ways to apply this to the JavaScript junk drawer problem. At least it's better than the previous method.
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What we used to have was a single megabyte file where everything got dumped into. I much prefer junk drawer development to trash bin development.
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The reason we got there was because we had the JavaScript include tag, which included everything.
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This made it easy to have all those files in one big directory since it would concatenate everything and cache it nicely.
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We solved the concatenation and speed problem, but we also made it very easy to create the mess you see now.
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This is a powerful insight: people will do what's easy.
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Right now, it's easy to write the script include tag and include everything.
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If we could somehow flip that around so that something else becomes easy, then we're on the right path.
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In any case, the conclusion is that treating JavaScript and stylesheets as second-class citizens is not a winning strategy.
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Web applications and web developers need to acknowledge that we can't ignore these assets.
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These divisions between front-end and back-end development shouldn't remain; they should blend.
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What’s the solution? It takes inspiration from what I believe is one of the greatest innovations of Ruby on Rails.
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Two pivotal innovations in Rails that encourage us to write clean applications are empty folders and empty files.
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When you have a place for everything, and it all has its place, everything feels nice.
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When everything is a big mess, you dread working with it, especially with that JavaScript folder.
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The 'Broken Window' theory applies when everything is piled together. No one cares for individual files when there’s mess.
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When everything is clean and organized, people care; no one wants to trash a pristine codebase.
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With the Asset Pipeline, we're introducing a collection of innovations: empty folders across different areas.
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The Asset Pipeline will deal efficiently with images, stylesheets, and JavaScripts, ensuring everything has a home.
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For instance, app/assets would house JavaScript that relates strictly to the application.
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Libraries that are not application-specific would reside in lib/assets, keeping things tidy.
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Finally, vendor assets would house third-party libraries.
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Just having three different places for these assets is a huge improvement.
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I went from having 40 files in one folder to about 15 in each. Below 13 still feels messy but is much better.
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The Asset Pipeline is highly extendable. You can set a new configuration in application.rb or in an initializer.
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You can easily add paths to your asset pipeline, making them accessible from anywhere.
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For example, if you take Disneyland as a source with a Goofy image, you can access that via the asset pipeline.
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Here’s an example of how I applied this while converting apps to Rails 3.1.
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I worked with a gem, signal ID, that manages all the login logic for our applications.
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The gem has an app/assets directory containing a JavaScript subdirectory with namespaced assets.
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This means we can hide JavaScript files that the app should not need to know about.
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Previously, you'd have to manually dump these files into the same junk drawer you've seen.
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Now, you just go to your application, find the app/assets/javascript folder, and require signal ID.
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By doing so, you ensure that the app gets only the necessary dependencies.
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This centralized management of dependencies through Bundler enables smoother operation for both JavaScript and stylesheets.
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Also, there's no need to manually copy assets into the public directory anymore.
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With Rails 3.1, the new jQuery Rails gem takes care of this and allows for easy integration.
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By keeping essential libraries organized, we can manage updates and dependencies much easier.
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This brings us to CoffeeScript, which is the new JavaScript framework default in Rails.
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There’s been a lot of discussion around making JavaScript development more user-friendly and enjoyable.
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CoffeeScript is a response to all of that, allowing for cleaner syntax and less boilerplate.
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Its substantial reductions in line noise create a friendlier development experience.
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For example, its use of significant whitespace creates clarity.
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This isn't to say that Ruby is abandoning its roots or its elements.
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Instead, it's expanding what developers can do and how they can do it.
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CoffeeScript allows us to move towards a more expressive JavaScript, enhancing its usability.
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As developers, we now have the capability to write cleaner, more maintainable code.
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This is not merely about writing JavaScript; it's about crafting a better experience overall.
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Let’s move forward with the Asset Pipeline, a solution bringing order to JavaScript and CSS.
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Thank you!
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