Shannon Deminick's blog all about web development

NDepend review = pretty cool!

June 21, 2013 23:47

For a while I’ve been wanting to automate some reporting from our build process to show some fairly simple statistical information such as

  • Obsoleted code
  • Internal code planned to be made public
  • Code flagged to be obsoleted
  • Code flagged as experimental

NOTE: some of the above are based on our own internal c# attributes

Originally I was just going to write some code to show me this which would have been fairly straight forward but I knew that NDepend had a code query language and natively outputs reports and can be integrated into the build process, so I figured I’d give it a go.

So I went and installed NDepend and ran the analysis against my current project … I wasn’t quite prepared for the amount of information it gave me! :)


I quickly found out that the reports that I wanted to create were insanely simple to write. I then lost a large part of my day exploring the reports it generates OOTB and I realized I hadn’t even touched the surface of the information this tool could give me. I was mostly interested in statistical analysis but this will also happily tell you about how bad or good your code is, how much test coverage you’ve got, what backwards compatibility you broke with your latest release, what code is most used in your project and what code isn’t used at all… and the list goes on and on.

To give you an example of the first report I wanted to write, here’s all I wrote to give me what methods in my codebase were obsoleted:

from m in JustMyCode.Methods where m.HasAttribute("System.ObsoleteAttribute") select m

What’s cool about the report output is that you can output to HTML or XML, so if you want to publish it on your site you can just write some XSLT to make it look the way you want.

Project comparison

Another really great feature that I thought would be fun to automate is the code analysis against previous builds so you know straight away if you are breaking compatibility with previous releases. I think it has great potential but what I did discover is that in some cases the OOTB queries for this aren’t perfect. It will tell you what public types, methods, and fields have been removed or changed and the query is pretty straightforward but… In many cases when we’re trying to maintain backwards compatibility while creating new APIs we’ll remove a type’s methods/properties and just make the legacy type inherit from the new API class (or some other trickery similar to that). This might break compatibility if people are using reflection or specific type checking but it wont break the API usage which I’m mostly interested in. I haven’t figured it out yet but I’m sure there’s some zany NDepend query I can write to check that.


So now that I know I can extract all this info, it’s time to decide what to export. Thankfully NDepend comes fully equipped with it’s own MSBuild integration so automating the report output should be pretty straightforward. I also noticed that if you wanted to be ultra careful you can integrate it with your build server and have your builds fail if some of your queries cause errors, like the above: If you break compatibility the build will fail. Or anything you want really, like failing the build if we detect you’ve written a method that has too many lines of code.

Pretty cool indeed!

I was going to use NDepend just to output reports which it clearly does without issue. What I didn’t realize was how much detail you can get about your code with this tool. There’s some tools in there that were a bit over my head but I suppose if you are working on really huge projects and need anything from just a snapshot or insane details into what dependencies your code has on other code it’ll do that easily as well.

The UI is a bit overwhelming at first and could probably do with some work but TBH I’m not sure how else you’d display that much information nicely. Once I figured out how the whole query and reporting structures work then it was dead simple.

Happy reporting :)