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Gotcha: MSBuild nested loops (double batching)

  • Articolo

I admit I didn’t get it on my first, quick, reading of “Inside the Microsoft Build Engine: Using MSBuild and Team Foundation Build” that MSBuild batching is somewhat counter-intuitive.

I needed to have a nested loop in my script, like this pseudo code:

 foreach (solution in solutionItemGroup) {

    foreach (configuration in solution.Configurations) {

        build solution's package using configuration

    }

}

It turned out that a naive solution doesn’t work: two different ItemGroup in the same Task are interpreted by MSBuild, like the following pseudo code:

 foreach (solution in solutionItemGroup) {

    build solution's package using configuration

}

foreach (configuration in solution.Configurations) {

    build solution's package using configuration

}

The solution I found is to work at the target level using a local property, an MSBuild 3.5 feature. MSBuild creates a first batch for the property, the outer loop, the a second, nested batch for the task at hand; some real code may better explain this.

 <Target Name="DeployToLocalServer" DependsOnTargets="MyResolveSolutionPaths">

    <PropertyGroup>

      <CurrentConfiguration>%(ConfigurationToBuild.FlavorToBuild)</CurrentConfiguration>

    </PropertyGroup>

    <MSBuild Projects="%(LocalSolutionToBuild.RootDir)%(LocalSolutionToBuild.Directory)%(LocalSolutionToBuild.Filename).Deployment.proj"

             Targets="Deploy"

             Properties="Configuration=$(CurrentConfiguration);OutDir=$(OutDir)"

             StopOnFirstFailure="$(StopOnFirstFailure)"

             ContinueOnError="false"

             Condition="'%(LocalSolutionToBuild.Deploy)'=='true'"

             />

</Target>

The CurrentConfiguration property batches (loops) on the ConfigurationToBuild; this property is used in the MSBuild task as a simple value ($ sign), and the interpreter over all its possible values before evaluating the batches in the task.

 

Happy Building!

Comments

  • Anonymous
    January 13, 2011
    This approach does not seem to work for me (in TFS 2010). Here I have outlined an approach which does work  kennyknecht.blogspot.com/.../nested-itemgroups-in-msbuild.html

  • Anonymous
    July 22, 2014
    So if we have a project with 4 Release Configurations and 3 Debug configurations, that loop is supposed to do for each Release and Debug. Can you please provide more detailed example? Thanks