Convention over confusion

November 19, 2013 . By Reuven

One of the most celebrated phrases that has emerged from Ruby on Rails is “convention over configuration.” The basic idea is that software can traditionally be used in many different ways, and that we can customize it using configuration files. Over the years, configuration files for many types of software have become huge; installing software might be easy, but configuring it can be difficult. Moreover, given the option, everyone will configure software differently. This means that when you join a new project, you need to learn that project’s specific configuration and quirks.

“Convention over configuration” is the idea that we can make everyone’s lives easier if we agree to restrict our freedom. Ruby on Rails does this by telling you precisely what your directories will be named, and where they will be located. Rails tells you what to call your database tables, your class names, and even your filenames. The Ruby language, while generally quite open and flexible, also enforces certain conventions: Class and module names must begin with capital letters, for example.

It can take some time for developers to accept these conventions. Indeed, I was one of them: When I first started to work with Rails, I was somewhat offended to be told precisely what my database column names would be, especially when those names contradicted advice that I had heard and adopted years ago. (The advice was to prefix every column in a database table with the name of the table, which would make it more easily readable in joins.  Thus the primary key of the “People” table would be person_id, followed by person_first_name, person_last_name, and so forth.)  Over time, I have grown not only to use these Rails conventions, but to enjoy working with them; it turns out that people can changes pretty easily, at least when it comes to these arbitrary decisions.

The real benefit of such conventions has nothing to do with my own work. Rather, it reduces the need for communication among people working on the same project. If everyone does it the same way, then there are fewer things to negotiate, and we can all concentrate on the real problems, rather than the ones which are relatively arbitrary.

Back in college, I was the editor of the student newspaper. We, like many newspapers, used the AP Stylebook to determine the style that we would use. The AP Stylebook was our bible; whatever it said, we did.  Of course, we also had our own local style, to cover things that AP didn’t, such as building names and numbers (e.g., we could refer to “Building 54″). In some cases, I personally disagreed with the AP Stylebook, especially when it came to the “Oxford comma.” But by keeping that rule, we were able to download articles from the Washington Post and LA Times, and stick them into our newspaper with minimal editing. Again, I prefer the serial comma, and use it in my personal writing. By adhering to a standard, I was able to ensure consistency in our writing, and reduce the workload of the (already hard-working) newspaper staff.

Twice in the last few weeks, I’ve been reminded of the benefits of convention over configuration — both times, when developers on projects I inherited decided to flout the rules. Their decisions weren’t wrong, but they were so wildly different from the conventions of Rails that they caused trouble, delays, and bugs.

The first case had to do with the Rails “asset pipeline,” a part of Rails which handles static assets such as JavaScript and CSS files. The idea is that you create a file called application.js, and that file then tells Rails about all of the JavaScript files used by your application. Before deploying a new version of your application, Rails combines all of these files into one big file, thus improving site performance (by reducing the number of files to download) and improving caching. The asset pipeline is a great idea, and it even works well — but in many cases, getting it to work correctly can be difficult and painful, particularly if you’re new to Rails.

So you can imagine my surprise when I looked for the application.js file, and didn’t find it.  That was bad enough, but the asset pipeline mechanism, as well as the deployment scripts I was developing, got rather confused by the absence of application.js. When I confronted the original developer about this, he told me that actually, he liked to call it something else entirely, reflecting the name of the application and client. Why? He didn’t really have a technical reason; it was all for reasons of aesthetics. The fact is that the rest of the Rails ecosystem expected application.js, though, so his decision meant that the rest of the software needed to be configured in a special, different way.

As a way of justifying his decision, the other developer told me, “Conventions shouldn’t be a boundary when developing.”  No, just the opposite — the idea is that conventions are there to limit you, to tell you to work in a way that everyone else works, so that things will be smoother.  In much of the world, we drive on the right side of the road.  This is utterly random; as numerous countries (e.g., England) have proven, you can drive on the other side of the road just fine — but only so long as everyone is doing it.  The moment everyone decides on their own conventions, big problems can occur.

When Biblical Hebrew wants to describe anarchy, it uses the phrase, “People did whatever was right in their own eyes.”

Something similar occurred with another project where I inherited code from someone else: One of my favorite things about Ruby on Rails is the fact that it runs the application in an “environment.”  The three standard environments are development (which is optimized for developer speed, not for execution speed), production (which is optimized for execution speed), and test (which is meant for testing). The environments aren’t meant to change the application logic, but rather the way in which the application behaves.  For example, I recently changed the way in which e-mail is sent to users of my dissertation software, the Modeling Commons. When I send the e-mail in the “production” environment, the e-mail is actually sent — but when I do so within the “development” environment, the e-mail is opened in a browser, so that I can examine it.  This is standard and expected behavior; all Rails applications have development, production, and test environments — and some even havea  “staging” environment, in which we prepare things.

My client’s software, which I inherited from someone else, decided to do something a bit different: The code was meant to be used on several different sites, each with slightly different logic.  The developer decided to use Rails environments in order to distinguish between the logical functions.  Thus, if you run the application under the “xyz” environment, you’ll get one logical path, and if you run the application under the “abc” environment, you’ll get another logical path.

It’s hard to describe the number of surprises and problems that this seemingly small decision has created: It means that we can’t really test the application using the normal Rails tools, because nothing will work correctly in the “test” environment. It means that the Phusion Passenger server that we installed to run the application needs an additional, special configuration parameter (not normally needed in production) to find the right database, and execute with the correct algorithms. It means that when you’re trying to trace through the logic of the application, you need to check the environment.

Basically, all of the things that you can assume about most Rails applications aren’t true in this one.

Now, the point of me writing this isn’t to say that I’m brilliant and that other developers are stupid — although it is true that Reuven’s First Law of Consulting states that a new consultant on a project must call his predecessor a moron.  Rather, it’s to point to the fact that conventions are there for a reason, and that if you insist on ignoring them, you’ll be increasing the learning curve that other developers will need to work on your application.  Now, if you have oodles of time and money, that’s just fine — but as a general rule, a developer’s time is a software company’s greatest expense, and anything you can do to increase productivity, and  decrease the need for explanations and communication, is worthwhile.

By the way, this is the whole reason why one of the Python mantras is, “There’s only one way to do it” — a direct contrast with the Ruby and Perl mantra, “There’s more than one way to do it.” Having a single, common way to do things makes everyone’s code more similar readable, and easier to understand. It doesn’t stop you from doing brilliant and interesting things, but does ask that you demonstrate your brilliance within the context of established practice.

Of course, this doesn’t mean that conventions are written in stone, or that they are unchangeable.  But if and when you ignore them, it should be for good reason.  Even if you’re right, think about whether you’re so right that it’s worth having multiple people learn your way of doing things, instead of the way that they’re used to doing them.

What do you think?  Have you see these sorts of issues in your work?  Let me know!

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