Tuesday, November 16, 2010

Migrating to FAKE

I finally finished migrating the SolrNet build scripts from MSBuild to FAKE. I did not do this out of a whim or just because I was bored, but because the MSBuild script was getting out of hand. At only 246 lines, it became unmaintainable. I admit I'm not a MSBuild expert, but a build script shouldn't be that hard. Just visually parsing the script was a daunting task.

This screenshot compares the FAKE and the equivalent MSBuild scripts side by side:


Even if you can't read it, I bet you can tell which is which.

XML-based DSLs like MSBuild and NAnt have only one advantage: being easily parsable by tools. But if you're going to do any sort of manual maintenance of the script, embedded DSLs in a real language will beat XML progamming every time.

I wrote the original build script for SolrNet in MSBuild for two reasons: no external dependencies, so it wouldn't place any burden on potential contributors; and being a NAnt user, I wanted to learn MSBuild.

But I should have known better: most of my NAnt scripts have evolved over the years to be mostly calls to MSBuild to compile solutions and embedded Boo to handle any logic.

Speaking of Boo, Phantom looks very nice. I picked FAKE over Phantom kind of arbitrarily, mostly because I'm really digging F# right now. But I'm keeping an eye on Phantom. Boo's macros and compiler extensibility are used in Phantom, and Boo's type inference and optional duck-typing make it an excellent language for a build system. And Boo is so small that you can fit the runtime and the compiler in under 2MB, so it's not an issue to distribute it.

Another option is Rake. Albacore and rake-dotnet implement the common .net-building tasks in Rake. But I really don't want to introduce a dependency on Ruby just to build the project.

Then there's PSake. PowerShell is quite powerful and I really like the concept of piping objects instead of lines of text as in unix shells. In the context of a build script, one of the main advantages of using a shell is that it's dead easy to call external programs, so "integrating" with ILMerge, Zip, etc is just a matter of calling the executable in question with the parameters you need, just as you would do it on the command line. No wrappers needed. And PowerShell is ubiquitous enough as to not consider it a dependency. But... I still can't get myself to like PowerShell's syntax. I know this is totally subjective, but I feel just like Jim here. Scripts involving .net are particularly ugly. And my first experience with PowerShell was bumpy to say the least.

Another (lesser for me) issue with PowerShell is that it currently doesn't run on Mono. It's not like I'm building SolrNet on Mono right now, but I certainly don't want to knowingly work against it.

So why did I pick FAKE and F# instead of all the others I mentioned?

  • F# is statically typed and has global type inference. If there is a type error in my script, it won't run. At the same time, type inference gives the code a scripty feel. I didn't have to declare a single type in the build script (you can see it here).
  • I can write my build script on VS2010, complete with intellisense, automatic error checking and debugging.
  • FAKE defines a simple, terse, functional EDSL to manage common build tasks.
  • FAKE is trivially extensible: just write a regular F# function (or .net method in any language) and invoke it. No particular structure or attributes needed. In just a few lines I defined some helper functions to manipulate XML and start/stop Solr to run integration tests.
  • F# works on Mono.
  • No external dependencies: F# is included in any default VS2010 install. And now that F# is Apache-licensed, it will soon be included in Mono (therefore also Ubuntu) and MonoDevelop.

I've also been contributing a few things to FAKE lately:

  • Enhancements to the MSBuild integration.
  • Enhancements to the ILMerge integration.
  • Gallio integration.
  • Simpler shell exec functions and some shell-like functions similar to Ruby's FileUtils.
  • A couple of bugfixes.

Bottom line: a few years ago all there was to build .net projects was MSBuild and NAnt. Nowadays there's a lot of choice. Make sure you do your research and pick the build system that's right for your project and for you.


Unknown said...

Do you use TFS server? if so how can you run FAKE scripts on it?

Mauricio Scheffer said...

@Dror Helper: please use the mailing list for questions about FAKE: http://groups.google.com/group/fsharpMake