Determine if MSBuild CoreCompile will run and call custom target

Question

This seems like an obvious thing to want to do but I have pulled most of my hair out trying to find any examples on the web or do it myself.

I have a c# solution with 19 projects and a Jenkins build server running a build script to drive MSBuild. MSBuild will of course determine what does and does not need to be compiled based on inputs versus outputs.

I am trying to create a custom target to conditionally update the AssemblyInfo.cs of those projects MSBuild is going to compile to increment the file versions. Of course I want to leave the projects not being compiled alone.

I know how to inject a target prior to the CoreBuild that runs every time so if there is some variable I can test to see if a compile will occur that can work. I also know how to determine if a compile ran and therefore conditionally do some post processing which is possible but not ideal.

How can I tweak my build process to achieve this?

Since it seems there's no straight answer to the question, does anyone know how to perform the same logic as MSBuild to determine what projects require a rebuild?

Answer 1

In the end the solution was a combination of Sayed Ibrahim Hashimi's blog entry and information from the MSDN Forum entry 'Execute target when (core)compile will execute'.

I basically took Sayed's injection method to get my target to run 'extend-corecompile.proj' on all projects without having to edit each proj file but replaced it's contents with an override for 'CoreCompileDependsOn' that points to a custom target that adopts the same inputs and outputs as the 'CoreCompile' target. The end result is a target that only runs when 'CoreCompile' will run while being centrally managed in the build script.

Thanks to all for their input and here is the skeleton code I used in 'extend-corecompile.proj':

<!--The following property group adds our custom post-target to the post compile call list -->
<PropertyGroup>
    <TargetsTriggeredByCompilation>
        $(TargetsTriggeredByCompilation);
        CustomPostTarget
    </TargetsTriggeredByCompilation>
</PropertyGroup>

<!--The following property group adds our custom pre-target to CoreCompileDependsOn to ensure it is called before CoreCompile -->
<PropertyGroup>
    <CoreCompileDependsOn>
        $(CoreCompileDependsOn);
        CustomPreTarget
    </CoreCompileDependsOn>
</PropertyGroup>

<!-- The following custom pre-target has the same inputs and outputs as CoreCompile so that it will only run when CoreCompile runs.
    Because we have injected this file and Targets are resolved in sequence we know this Target will fire before CoreCompile.-->
<Target Name="CustomPreTarget" 
    Inputs="$(MSBuildAllProjects);
            @(Compile);                               
            @(_CoreCompileResourceInputs);
            $(ApplicationIcon);
            $(AssemblyOriginatorKeyFile);
            @(ReferencePath);
            @(CompiledLicenseFile);
            @(EmbeddedDocumentation); 
            $(Win32Resource);
            $(Win32Manifest);
            @(CustomAdditionalCompileInputs)"
    Outputs="@(DocFileItem);
             @(IntermediateAssembly);
             @(_DebugSymbolsIntermediatePath);                 
             $(NonExistentFile);
             @(CustomAdditionalCompileOutputs)">
    <!--Do pre-compilation processing here-->
</Target>

<!--This target will be called by CoreCompile-->
<Target Name="CustomPostTarget" >
    <!--Do post-compilation processing here-->
</Target>

Not sure what will happen if CoreCompile fails, does it still call our target? I guess in time we'll find out :)

Answer 2

I just blogged the answer to this at http://sedodream.com/2012/07/28/MSBuildHowToExecuteATargetAfterCoreCompilePart2.aspx but I've pasted the solution for you below.

A couple of months ago I wrote a blog post MSBuild how to execute a target after CoreCompile in which I describe how you can execute a target if the CoreCompile target is executed, if CoreCompile is skipped then so will your other target. The draw back of the approach that I outlined in my previous post was that it required you to edit your .csproj/.vbproj/etc file itself. So if you had a scenario where you were building multiple projects then you would have to edit all of the project files. In this post I’ll describe how you can perform the same customization without having to edit the project file itself.

Before we get to the solution for this particular case let me describe an extensibility hook that the C# and VB projects have. Most of the logic for building C# and VB projects is captured in the MSBuild targets file at C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets. If you take a look in that file you will notice at the top an import looking like the one below.

<Import Project="$(CustomBeforeMicrosoftCommonTargets)" Condition="'$(CustomBeforeMicrosoftCommonTargets)' != '' and Exists('$(CustomBeforeMicrosoftCommonTargets)')"/>

This statement will import a file (located at the value for CustomBeforeMicrosoftCommonTargets) if the property is not empty and the file exists. The default value for CustomBeforeMicrosoftCommonTargets is C:\Program Files (x86)\MSBuild\v4.0\Custom.Before.Microsoft.Common.targets. So if you drop an MSBuild file at that location it will modify the build process for every C#/VB project built on that machine. Alternatively if you do not want (or cannot due to ACLs) then you can drop the file somewhere else and then specify its location by overriding the CustomBeforeMicrosoftCommonTargets property. This is the approach that I will take here. I have created a sample solution which consists of two projects ProjA and ProjB. I also have a build script, build.proj, to automate the build for this. Below is the entire contents of build.proj.

build.proj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <FileToInject Condition=" '$(FileToInject)'=='' ">$(MSBuildThisFileDirectory)extend-corecompile.proj</FileToInject>
  </PropertyGroup>

  <ItemGroup>
    <ProjectsToBuild Include="ProjA\ProjA.csproj"/>
    <ProjectsToBuild Include="ProjB\ProjB.csproj"/>
  </ItemGroup>

  <Target Name="Build">
    <MSBuild Projects="@(ProjectsToBuild)"
             Properties="CustomBeforeMicrosoftCommonTargets=$(FileToInject)" />   
  </Target>

  <Target Name="Clean">
    <MSBuild Projects="@(ProjectsToBuild)" Targets="Clean"/>
  </Target>

  <Target Name="Rebuild" DependsOnTargets="Clean;Build"/>

</Project>

In the Build target above I use the MSBuild task to build both ProjA and ProjB. As you can see I am passing the property CustomBeforeMicrosoftCommonTargets=$(FileToInject) which points to extend-corecompile.proj. By passing this property when ProjA, and ProjB, is built it will automatically import the extend-corecompile.proj file for the build process. You can see the contents of extend-corecompile.proj below.

extend-corecompile.proj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <TargetsTriggeredByCompilation>
      $(TargetsTriggeredByCompilation);
      MyCustomTarget
    </TargetsTriggeredByCompilation>
  </PropertyGroup>

  <Target Name="MyCustomTarget">
    <Message Text="MyCustomTarget called" Importance ="high"/>
  </Target>

</Project>

This project file uses the technique outlined in my previous blog post to execute the MyCustomTarget only if CoreCompile is executed.

Note: You can get the latest version of this sample at https://github.com/sayedihashimi/sayed-samples/tree/master/ExtBuildMultiple.