MsBuild finding directories if not given as parameter

I’m a lazy developer. Being lazy does not mean I avoid to work. It means that I like to reflect things I am doing and optimize and atomize stuff to get more time on the valuable tasks. Code generation is a tool I tend to use quite regularly and T4 is at most my generator of choice.

Generated files can cause a lot of merging conflicts. So they are not to be checked into my source control system (currently my choice is HG/Mercurial).

For the build server this means the files do not exist when the repository is freshly checked out – they need to be generated during the build right before the compile happens.

With code generation I usually tend to use a pattern that is for example also used by ASP.NET MVC Views/Controller generation: If there is a local directory containing code generation templates, use it. Otherwise utilize the system wide templates.

MsBuild version 4.0 comes with a feature called property functions. This allows to place for instance a “find directories” inside a property group.

I use them to:

  • Allow to set a system wide template directory using the command line/the MsBuild API.
  • If no directory is set use a local directory.
  • If non of the above is applied set a fallback default.

Here is the XML snippet that shows how to use the pattern:

<?xml version="1.0" encoding="utf-8"?>
<Project
    DefaultTargets="Generate"
	ToolsVersion="4.0"
	xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

	<PropertyGroup>
		<RootFolder>..\src</RootFolder>
		<CodeGeneratorDir
			Condition=" '$(CodeGeneratorDir)' == '' " />
		<LocalCodeGeneratorDir>
			CodeGenerationTemplates
		</LocalCodeGeneratorDir>
		<CodeGeneratorDirFallback>
			C:\CodeGenerationTemplates
		</CodeGeneratorDirFallback>
	</PropertyGroup>

	<ItemGroup>
		<ModelFiles
			Include="..\src\**\*.xdml"
		/>
		<TemplateDirectory
			Include="$(CodeGeneratorDir);"
		/>
		<TemplateDirectory
			Condition=" '$(CodeGeneratorDir)' == '' "
			Include="$([System.IO.Directory]::GetDirectories(
				&quot;$(RootFolder)&quot;,
				&quot;$(LocalCodeGeneratorDir)&quot;,
				System.IO.SearchOption.AllDirectories))"
		/>
		<TemplateDirectory
			Condition=" '@(TemplateDirectory)' == '' "
			Include="$(CodeGeneratorDirFallback)"
		/>
	</ItemGroup>

	<Target Name="Generate">
		<Message Text="@(TemplateDirectory)" />
		<Message Text="@(ModelFiles)" />
  </Target>

</Project>

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