Stories about Software


Good Magic and Bad Magic

Not too long ago, I was working with a web development framework that I had inherited on a project, and I was struggling mightily with it to get it to work. The functionality was not discoverable at all, and it was provided almost exclusively via inheritance rather than composition. Runtime debugging was similarly fruitless, as a great deal of functionality was obfuscated via heavy use of reflection and a lot “squishing” of the application to fit into a forms over data paradigm (binding the GUI right to data sources, for instance). Generally, you would find some kind of prototype class/form to look at, try to adapt it to what you were doing and struggle for a few hours before reverse engineering the fact that you weren’t setting some random property defined in an ancestor class properly. Until you set this string property to “asdffdsa,” absolutely nothing would work. When you finally figured out the answer, the reaction wasn’t one of triumph but indignation. “Really?!? That’s what just ate the last two hours of my life?!?”

I remember a different sort of experience when I started working Web API. With that technology, I frequently found myself thinking things like “this seems like it should work,” and then, lo and behold, it did. In other words, I’d write a bit of code or give something a name that I figured would make sense in context, and things just kind of magically worked. It was a pretty heady feeling, and comparing these two experiences is a study in contrast.

One might say that this a matter of convention and configuration. After all, having to set some weird, non-discoverable string property is really configuration, and a lot of the newer web frameworks, Web API included, rely heavily on convention. But I think it goes beyond that and into the concepts that I’ll call “good and bad magic.” And the reason I say it’s not the same is that one could pretty easily establish non-intuitive conventions and have extremely clear, logical configurations.

When I talk about “magic,” I’m talking about things in a code base or application behind the scenes. This is “magic” in the sense that you can’t spell “automagically” without “magic.” In a MVC or Web API application, the routing conventions and ways that views and controllers are selected are magic. You create FooController and FooView in the right places, and suddenly, when you navigate to app/Foo, things just work. If you want to customize and change things, you can, but it’s not a battle. By default, it does what it seems like it ought to do. The dark side of is the application I described in the first paragraph — the one in which all of the other classes were working because of some obscure setting of a cryptically named property defined in a base class. When you define your own class, everything blows up because you’re not setting this property. It seems like a class should just work, but due to some hidden hocus-pocus, it actually doesn’t.

The reason I mention all this is to offer some advice based on my own experience. When you’re writing code for other developers (and you almost always are because, sooner or later, someone besides you will be maintaining your code or invoking it), think about whether your code hides some magic from others. This will most likely be the case if you’re writing framework or utility code, but it can always apply. If your code is, in fact, doing things that will seem magical to others, ask yourself if it’s good magic or bad magic. A good way to answer this question for yourself is to ask yourself how likely you think it will be that you’ll need to explain what’s going on to people that use your code. If you find yourself thinking, “oh, yeah, they’ll need some help — maybe even an instruction manual,” you’re forcing bad magic on them. If you find yourself thinking, “if they do industry standard things, they’ll figure it out,” you might be in good shape.

I say you might be in good shape because it’s possible you think others will understand it, but they won’t. This comes with practice, and good magic is hard. Bad magic is depressingly easy. So if you’re going to do some magic for your collaborators, make sure it’s good magic because no magic at all is better than bad magic.

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4 Comments on "Good Magic and Bad Magic"

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Geoff Mazeroff

Reminds me a bit of the phrase “falling into the pit of success,” which is a goal when writing anything, especially an API. Thanks for sharing your thoughts!

Erik Dietrich

I really like that phrase a lot. I think it’s an important thing to strive for, especially if you’re a senior or architect type. To me, that’s the mark of a highly productive team member — one that makes it so other team members can’t help but succeed.

Thomas Lassanske

“Falling into the pit of success” would be the opposite of “climbing the mountain of fail”. 😉

Erik Dietrich