Today I started writing my first build scripts in Ruby for a .NET project using Rake. This is what I came up with.

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require 'rake/clean'

EXTERNALS_DIR = File.expand_path('../Externals')
BUILD_DIR = File.expand_path('../Bin')
SOURCE_DIR = File.expand_path('../Source')
CLEAN.include(FileList[File.join(BUILD_DIR, '*')])

desc "Compiles the gemini sources"
task :build do
  gemini_solution = File.join(SOURCE_DIR, 'Gemini.sln')
  sh "msbuild /property:WarningLevel=4;OutDir=#{BUILD_DIR}/ #{gemini_solution}"
end

desc "Runs all the tests on the gemini code"
task :test do
  assemblies = all_spec_assemblies()
  xunit_console = File.join(EXTERNALS_DIR, "xUnit/xunit.console.exe")
  assemblies.each do |assembly|
      sh "#{xunit_console} #{assembly} /html #{assembly +'.UnitTests.html'}"
  end
end

task :default => [:clean, :build, :test]

def all_spec_assemblies()
  file_mask = File.join(BUILD_DIR, '*Specs.dll')
  FileList[file_mask]
end

I think this code demonstrates the qualities of Ruby as a scripting language and Rake as a build tool really well. It’s very descriptive and even more important it doesn’t have all the xml-slash-what-the-hell-is-going-on-here-noise around it. I know it’s a very simple solution, but I consider it a good start. Let’s look a bit more detailed at the parts of the script.

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EXTERNALS_DIR = File.expand_path('../Externals')
BUILD_DIR = File.expand_path('../Bin')
SOURCE_DIR = File.expand_path('../Source')

This part defines some directory constants that are used in the script. The rakefile is currently run from the directory ‘Build’ which is on the same level as ‘Externals’, ‘Bin’ and ‘Source’. Relative paths are expanded to absolute paths here.

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CLEAN.include(FileList[File.join(BUILD_DIR, '*')])

This tiny little code piece modifies the built-in :clean task and adds all files under the BUILD_DIR to it. Running ‘rake clean’ on the console will now delete all files from our build directory.

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desc "Compiles the gemini sources"
task :build do
  gemini_solution = File.join(SOURCE_DIR, 'Gemini.sln')
  sh "msbuild /property:WarningLevel=4;OutDir=#{BUILD_DIR}/ #{gemini_solution}"
end

This is the first task I’ve actually written on my own. It’s only a very small wrapper around msbuild that builds the solution file.

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desc "Runs all the tests on the gemini code"
task :test do
  assemblies = all_spec_assemblies()
  xunit_console = File.join(EXTERNALS_DIR, "xUnit/xunit.console.exe")
  assemblies.each do |assembly|
      sh "#{xunit_console} #{assembly} /html #{assembly +'.UnitTests.html'}"
  end
end

def all_spec_assemblies()
  file_mask = File.join(BUILD_DIR, '*Specs.dll') FileList[file_mask]
end

That little code is a small wrapper around xUnit.net which invokes the xunit.console.exe for each file it finds in the build directory that ends with ‘Spec.dll’. These are the assemblies which contain the BDD-style tests in our project.

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task :default => [:clean, :build, :test]

This last piece defines the :default build task. That’s the task which is run when you don’t specify a task directly when running rake from console. This will run all tasks in the order specified from left to right.

Conclusion

The Rake build engine rocks !!! Its really simple and descriptive API is fun and Rake doesn’t create a lot of ceremony around build scripts (Only around 30 lines of code in my current script). However, you should be aware of one thing: Coming from a language with a lot of IDE support (like C# in my case) to Ruby might not be as easy as it sounds. It took me quite a while to make the transition from Intellisense and Resharper to using IRB and reading RDoc in order to explore new APIs …