What's Up With All These Changes in Rails?

Yesterday, there was a blog post entitled "What the Hell is Happening to Rails" that stayed at the number one spot on Hacker News for quite a while. The post and many (but not most) the comments on the post reflect deep-seated concern about the recent direction of Rails. Others have addressed the core question about change in the framework, but I'd like to address questions about specific changes that came up in the post and comments.

The intent of this post is not to nitpick the specific arguments that were made, or to address the larger question of how much change is appropriate in the framework, but rather to provide some background on some of the changes that have been made since Rails 2.3 and to explain why we made them.

Block Helpers

I too get a feeling of "change for the sake of change" from Rails at times. That's obviously not something they're doing, as all the changes have some motivation, but at times it feels a bit like churn. At one point in time, you did forms like <%= form .... and then they switched to <% form .... do and now they've switched back to <%= form ... do again. Also, the upgrade to Rails 3 is not an easy one. Yeah, you get some nice stuff, but because it's so painful, it's not happening for a lot of people, which is causing more problems.

Prior to Rails 3.0, Rails never used <= form_for because it was technically very difficult to make it work. I wrote a post about it in Summer 2009 that walked through the technical problems. The short version is that every ERB template is compiled into a Ruby method, and reliably converting &lt%= with blocks proved to be extremely complicated.

However, knowing when to use <% and when to use <= caused major issues for new developers, and it was a major 3.0 priority to make this work. In addition, because of the backwards compatibility issue, we went to extreme Ruby-exploiting lengths to enable deprecation warnings about the change, so that we could fix the issue for new apps, but also not break old apps.

The night José and I figured out how to do this (the Engine Yard party at Mountain West RubyConf 2009), we were pretty close to coming to the conclusion that it couldn't be done short of using a full language parser in ERB, which should give you some sense of how vexing a problem it was for us.


The general disregard for improving performance, inherited from Ruby, is also something endemic from a while back.

Yes, there have been some performance regressions in Rails 3.0. However, the idea that the Rails core team doesn't care about performance, and neither does the Ruby team doesn't pass the smell test.

Aaron Patterson, the newest core team member, worked full time for almost a year to get the new ActiveRecord backend into decent performance shape. Totally new code often comes with some performance regressions, and the changes to ActiveRecord were important and a long-time coming. Many of us didn't see the magnitude of the initial problem until it was too late for 3.0, but we take the problem extremely seriously.

Ruby core ("MRI") itself has sunk an enormous amount of time into performance improvements in Ruby 1.9, going so far as to completely rewrite the core VM from scratch. This resulted in significant performance improvements, and the Ruby team continues to work on improvements to performance and to core systems like the garbage collector.

The Ruby C API poses some long-term problems for the upper-bound of Ruby performance improvements, but the JRuby and Rubinius projects are showing how you can use Ruby C extensions inside a state-of-the-art virtual machine. Indeed, the JRuby and Rubinius projects show that the Ruby community both cares about, and is willing to invest significant energy into improving the performance of Ruby.

Heroku and the Asset Pipeline

The assets pipeline feels horrible, it's really slow. I upgraded to Rails 3.1rc, realized it fights with Heroku unless upgrading to the Cedar stack

The problem with Heroku is that the default Gemfile that comes with Rails 3.1 currently requires a JavaScript runtime to boot, even in production. This is clearly wrong and will be fixed posthaste. Requiring Rails apps to have node or a compiled v8 in production is an unacceptable burden.

On the flip side, the execjs gem, which manages compiling CoffeeScript (and more importantly minifying your JavaScript), is actually a pretty smart piece of work. It turns out that both Mac OSX and Windows ship with usable JavaScript binaries, so in development, most Rails users will already have a JavaScript library ready to use.

It's worth noting that a JavaScript engine is needed to run "uglify.js", the most popular and most effective JavaScript minifier. It is best practice to minify your JavaScript before deployment, so you can feel free to format and comment your code as you like without effecting the payload. You can learn more about minification in this excellent post by Steve Souders from a few years back. Rails adding minification by default is an unambiguous improvement in the workflow of Rails applications, because it makes it easy (almost invisible) to do something that everyone should be doing, but which has previously been something of a pain.

Again, making node a dependency in production is clearly wrong, and will be removed before the final release.

Change for Change's Sake

The problem with Rails is not the pace of change so much as the wild changes of direction it takes, sometimes introducing serious performance degradations into official releases. Sometimes it's hard to see a guiding core philosophy other than the fact they want to be on the shiny edge

When Rails shipped, it came with a number of defaults:

  • ActiveRecord
  • Test::Unit
  • ERB
  • Prototype

Since 2004, alternatives to all of those options have been created, and in many cases (Rspec, jQuery, Haml) have become somewhat popular. Rails 3.0 made no changes to the defaults, despite much clamoring for a change from Prototype to jQuery. Rails 3.1 changed to jQuery only when it became overwhelmingly clear that jQuery was the de facto standard on the web.

As someone who has sat in on many discussions about changing defaults, I can tell you that defaults in Rails are not changed lightly, and certainly not "to be on the shiny edge." In fact, I think that Rails is more conservative than most would expect in changing defaults.

Right, but the problem is that there doesn't seem to be a 'right' way, That's the problem. We were all prototype a few years ago, now it jquery ... we (well I) hadn't heard of coffeescript till a few months ago and now its a default option in rails, The way we were constructing ActiveRecord finders had been set all through Rails 2, now we've changed it, the way we dealt with gems was set all through rails 2 now its changed completely in Rails 3. I like change, I like staying on the cutting edge of web technologies, but I don't want to learn something, only to discard it and re-do it completely to bring it up to date with a new way of doing things all the time.

First, jQuery has become the de facto standard on the web. As I said earlier, Rails resisted making this change in 3.0, despite a lot of popular demand, and the change to jQuery is actually an example of the stability of Rails' default choices over time, rather than the opposite.

Changes to gem handling evolved as the Rails community evolved to use gems more. In Rails 1, all extensions were implemented as plugins that got pulled out of svn and dumped into your project. This didn't allow for versioning or dependencies, so Rails 2 introduced first-class support for Rails plugins as gems.

During the Rails 2 series, Rails added a dependency on Rack, which caused serious problems when Rails was used with other gems that rely on Rack, due to the way that raw Rubygems handles dependency activation. Because Rails 3 uses gem dependencies more extensively, we spent a year building bundler, which adds per-application dependency resolution to Rubygems. This was simply the natural evolution of the way that Rails has used dependencies over time.

The addition of CoffeeScript is interesting, because it's a pretty young technology, but it's also not really different from shipping a new template handler. When you create a new Rails app, the JavaScript file is a regular JS file, and the asset compilation and dependency support does not require CoffeeScript. Shipping CoffeeScript is basically like shipping Builder: should you want it, it's there for you. Since we want to support minification out of the box anyway, CoffeeScript doesn't add any new requirements. And since it's just there in the default Gemfile, as opposed to included in Rails proper like Builder, turning it off (if you really want to) is as simple as removing a line in your Gemfile. Nothing scary here.

ActiveRecord Changes

The way we were constructing ActiveRecord finders had been set all through Rails 2, now we've changed it


The Rails core team does seem to treat the project as if it's a personal playground

One of the biggest problems with ActiveRecord was the way it internally used Strings to represent queries. This meant that changes to queries often required gsubing String to make simple changes. Internally, it was a mess, and it expressed itself in the public API in how conditions were generated, and more importantly how named scopes were created.

One goal of the improvements in Rails 3 was to get rid of the ad-hoc query generation in Rails 2 and replace it with something better. ActiveRelation, this library, was literally multiple years in the making, and a large amount of the energy in the Rails 3.0 process was spent on integrating ActiveRelation.

From a user-facing perspective, we wanted to unify all of the different ways that queries were made. This means that scopes, class methods, and one-time-use queries all use the same API. As in the <= case, a significant amount of effort was spent on backwards compatibility with Rails 2.3. In fact, we decided to hold onto support for the old API as least as long as Rails 3.2, in order to soften the community transition to the new API.

In general, we were quite careful about backwards compatibility in Rails 3.0, and while a project as complex as Rails was not going to be perfect in this regard, characterizing the way we handled this as "irresponsible" or "playground" disregards the tremendous amount of work and gymnastics that the core team and community contributors put into supporting Rails 2.3 APIs across the entire codebase when changes were made.