I switched to Ruby and Rake for my .NET build over the last few months and it’s been freakin’ awesome! I came from msbuild .targets and “programming in XML”. I’ve basically stumbled upon a successful rake build along the way (and copied liberally from other projects). You can reference the whole thing and I’ll snip in each section as I explain it.

Running on the Windows command line

For .NET projects, having a Ruby environment on your workstation or on the build agent is probably uncommon. I recommend checking in a complete Ruby environment (use one of the zip archives). You should make a few batch files to invoke the Ruby/Rake toolset really easily.

CALL "%~dp0\ruby\bin\rake.bat" %*

This will call the Rake batch file in your Ruby environment, which is setup to invoke the Rake application. It defaults to using rakefile.rb and the default task. You can make other batch files to easily invoke other tasks/configurations. For example, a Debug build of the CI tasks…

CALL "%~dp0\build.bat" configuration=Debug ci %*

Let’s jump into the rakefile to see how some of those parameters are handled.

configuration = ENV['configuration'] || 'Release'
version       = ENV['version'] || '0.0.5.0'

These lines will check the environment variables, including anything passed in on the command line, or use the default. Here I’m allowing a ‘configuration’ (for an msbuild task, more on that later) and a ‘version’ to come in from the outside world (my build engine).

Safe paths for Windows

Unfortunately, a lot of Windows applications, even native commands, do not handle relative file paths well. It certainly adds extra code every time you work with a path, but it’s going to save you in the long run.

I start by defining the solution root, which is where my rakefile lives. And any other paths that will be commonly used throughout this build. I also put any static paths that might need to be changed per-branch front and center so they’re easier to change.

solution_root = File.expand_path(File.dirname(__FILE__))
output_path   = File.join(solution_root, "bin/#{configuration}")
drop_root     = '//development-nas/my-project/trunk'

Some Windows applications don’t even respect the POSIX forward-slash directory separator. A helper method like this goes a long way in a Windows build.

def windows_path(path)
    path.gsub('/', '\\')
end

We have this method because we have some files, CommonAssemblyInfo and others (coming up), that need to be modified. But, because we’re using TFS, the files on the build agent are read-only. And I have no intention of checking these back in, so tf checkout #{path} is overkill (and requires undo or checkin, not interested).

def un_tfs(path)
    if File.exists?(path)
        File.chmod(644, path)
        puts "Making #{path} writeable"
    end
end

Clean/Clobber and FileLists

The FileList is a lazy file collection defined by “glob”, or wildcard, patterns. And it supports a ton of great transformations. They’re great when you need to use a list in multiple tasks. If you define a regular list for, say, the specs and publish_specs tasks… this will execute immediately, before running the build task.

spec_assemblies = Dir.glob("./#{output_path}/*.Specifications.dll")

You’ll get a list of 0 items, or worse, if you didn’t clobber the last build’s output, you could get the last build’s list. And that can wreak havoc when your next build adds/removes expected spec assemblies. Define it instead with FileList and it won’t be resolved until you iterate over it.

spec_assemblies = FileList["./#{output_path}/*.Specifications.dll"]

The rake/clean file defines two built-in FileLists, CLEAN & CLOBBER, used in built-in tasks, clean & clobber. Read the documentation and understand the difference. Clobber is dead simple when you have a single OutputPath (in msbuild parlance).

CLOBBER = FileList["./#{output_path}/*"]

Finally, the tasks!

The default task must be defined and is used when you run rake without any parameters. I like this to be quick, but useful, usually a simple build & test. I’ll define the exact TeamCity build tasks here, too, so that my configuration is one step: Rake runner; task = ‘ci’ or ‘release’.

task :default => [ :clean, :build, :test ]
task :ci      => [ :clobber, :assemblyinfo, :build, :test,                :xmlupdate, :deploy ]
task :release => [ :clobber, :assemblyinfo, :build, :test, :verification, :xmlupdate, :deploy, :msi ]

I’m doing a lot of common .NET build tasks. You can reference the Albacore wiki for information on the build, assemblyinfo, and test tasks. I’m using a custom task of my own for rewriting the VC++ application resource and C# application configuration files. And the deploy & prune task is another package I maintain.

Let’s look at one tricky task, made possibly by Ruby dynamism, the verification_tests task. Notice how it depends on (=>) an array of strings defined earlier? Those correspond to mspec tags that we use to categorize special tests. We need to provide a test results report for each tag… we could try to define each task individually

mspec :lct_tests => :build do |mspec|
  results_path = File.join(output_path, "LCT_#{version}.verificationresults.html")
  mspec.options ["--html \"#{results_path}\"", "--include \"LCT\""]
  mspec.assemblies mspec_assemblies
end

mspec :fat_tests => :build do |mspec|
  results_path = File.join(output_path, "FAT_#{version}.verificationresults.html")
  mspec.options ["--html \"#{results_path}\"", "--include \"FAT\""]
  mspec.assemblies mspec_assemblies
end

But, look at the duplication! Instead, because we know that we want the same exact task parameters, we’ll loop through the array and dynamically create a task per name!

verification_test_tags.each do |name|
  mspec name => :build do |mspec|
    results_path = File.join(output_path, "#{name}_#{version}.verificationresults.html")
    mspec.options ["--html \"#{results_path}\"", "--include \"#{name}\""]
    mspec.assemblies mspec_assemblies
  end
end

What’s next?

You should dive headfirst into Albacore! And stay tuned, because I’ll post some enhancements in the coming weeks/months…

  • Commit the apprc and appconfig tasks to Albacore
  • Manage and publish the version from inside this build
  • Extract the TeamCity methods into a gem
  • Wrap the InstallShield stuff into a gem