Rarely does a blog post get me all fired up like Giles Bowketts here. As part of the team working on improving debugging support for JRuby, it probably struck a particularly personal chord. Nothing like having your hard work publicly ridiculed to get you exicted. I might have ignored it, and maybe I probably should, but the post contains some truly exceptional BS that needs to be addressed.
First off, it claims to inspired by a good friend of mine. So Giles, to quote from that famous vice presedential debate: I know Jim Weirich, and you sir, are no Jim Weirich! Ok, so maybe Giles didn't actually claim to be Jim Weirich, but the fact that he even attributed Jim in any way while spouting such blatent poppycock just shouldn't be.
As part of my job I have the incredible good fortune to pair with Jim on a Rails project. At the risk of pointing out what should be obvious, we do write test cases. And, it's true, when we first started working together, we did not use a debugger. Most of the time, we didn't need one. But every so often, we would have a situation where we couldn't understand what some code was doing. More embarrassing still, sometimes it was even code that we wrote.
So, when confronted with such a situation, when we couldn't think of any more test cases to write, we would add statements like this to our code "puts DBG: #{some_value_we_want_to_see}". Wow, perty high tech, eh? And it worked. We could always solve our problem this way. Jim even had a little rake task that would comb thru the code to find DBG: in our code so we could easily remove these when we were done.
Then one day I got tired of us typing DBG: in our code and I said something like "Let's try using rdebug". And guess what: rdebug was often handier than adding puts statements to our code. We could inspect all kinds of stuff. Sometimes it helped us learn more about how Rails works, especially when it did things that were, umm, a little unexpected. It was a good thing. So much so, in fact, Jim spent some time working on getting it working better with emacs so it was even easier to use.
And, hard to believe tho it may be, it did not cause us to write less test cases. Every time we learned something while debugging, we could go back and write a test case which documented our learning. In the end it helped us to write more and better test cases because we were actively trying to do so.
So it should be obvious, but since it didn't seem to be I'll state it: debuggers are tools. Like any tool, if it helps you do your work better, you might want to use it. If it doesn't you probably shouldn't. Using a tool does not lead to bad habits, bad habits lead to using a tool incorrectly. And it's worth pointing out, the technique of classifying a technology or tool as bad because it can be used incorrectly is exactly the argument that I hear made against metaprogramming and run time type checking. Kind of ironic.
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