MSBuild - Comparing ItemGroups metadata

Question

I am attempting to write a build script for our source tree. This tree consists of a (large) number of solutions with assembly references between them. I have created an I

Answer 1

Ah. Stumbled on an answer whilst playing around with this.

Firstly, I was investigating this post about getting the intersection of two item groups. I therefore changed my OutputNames item group to have the same Identity as the OutputProjects ItemGroup:

<OutputNames Include="$(MSBuildProjectDirectory)\Solution1\Project1A\Project1A.csproj">
  <OutputFolder>ArbitraryFolder1</OutputFolder>
</OutputNames>
<OutputNames Include="$(MSBuildProjectDirectory)\Solution2\Project2B\Project2B.csproj">
  <OutputFolder>ArbitraryFolder2</OutputFolder>
</OutputNames>

This let me batch on %(Identity) and get the intersection like this:

<Message Condition="'%(Identity)' != '' and
         '@(OutputProjects)' != '' and
         '@(OutputNames)' != ''"
         Text="Found a match for %(Identity)" />

However, when also referring to the OutputFolder metadata in the same Task, that became part of the batching as well resulting in the following never printing to the output:

<Message Condition="'%(Identity)' != '' and
         '@(OutputProjects)' != '' and
         '@(OutputNames)' != ''"
         Text="Found a match for %(Identity): %(OutputNames.OutputFolder)" />

But, by using a transform over the property instead of direct access, it isn't treated as part of the batching:

<Message Condition="'%(Identity)' != '' and
         '@(OutputProjects)' != '' and
         '@(OutputNames)' != ''"
         Text="Found a match for %(Identity): @(OutputNames->'%(OutputFolder)')" />

Therefore, I can do the following to update my metadata:

  <!-- Now override specific projects OutputTo metadata -->
  <OutputProjects Condition="'%(Identity)' != '' AND
                             '@(OutputProjects)' != '' AND
                             '@(OutputNames)' != ''">
    <OutputTo>@(OutputNames->'%(OutputFolder)')</OutputTo>
  </OutputProjects>