如何从 MSBuild 目标修改 ItemDefinitionGroup？

Question

我编写了一个 msbuild 脚本来编译 Google Protocol Buffers 文件：

<ItemGroup>
  <ProtocolBuffer Include="Whitelist.proto" />
  <ProtocolBuffer Include="Whitelist2.proto" />
</ItemGroup>
<ItemDefinitionGroup>
  <ProtocolBuffer>
    <ProtoPath>$(ProjectDir)</ProtoPath>
  </ProtocolBuffer>
</ItemDefinitionGroup>
<PropertyGroup>
  <ProtoC>$([System.IO.Path]::GetFullPath($(ProjectDir)..\ThirdParty\protobuf-2.4.1\protoc.exe))</ProtoC>
  <ProtoOutPath>$(IntDir)CompiledProtocolBuffers</ProtoOutPath>
</PropertyGroup>
<Target Name="CompileProtocolBuffers"
        BeforeTargets="ClCompile"
        Inputs="@(ProtocolBuffer)"
        Outputs="@(ProtocolBuffer->'$(ProtoOutPath)\%(FileName).pb.cc');@(ProtocolBuffer->'$(ProtoOutPath)\%(FileName).pb.h')">
  <MakeDir Directories="$(ProtoOutPath)" />
  <Exec
    Command="&quot;$(ProtoC)&quot; --proto_path=&quot;$([System.IO.Path]::GetDirectoryName(%(ProtocolBuffer.ProtoPath)))&quot; --cpp_out=&quot;$(ProtoOutPath)&quot; &quot;%(ProtocolBuffer.FullPath)&quot; --error_format=msvs"
        />
  <ItemGroup>
    <ClInclude Include="$(ProtoOutPath)\%(ProtocolBuffer.FileName).pb.h" />
    <ClCompile Include="$(ProtoOutPath)\%(ProtocolBuffer.FileName).pb.cc">
      <AdditionalIncludeDirectories>$(MSBuildThisDirectory)..\ThirdParty\protobuf-2.4.1\src</AdditionalIncludeDirectories>
      <PrecompiledHeader></PrecompiledHeader>
      <DisableSpecificWarnings>4244;4276;4018;4355;4800;4251;4996;4146;4305</DisableSpecificWarnings>
      <PreprocessorDefinitions>GOOGLE_PROTOBUF_NO_RTTI</PreprocessorDefinitions>
      <WarningLevel>Level3</WarningLevel>
    </ClCompile>
  </ItemGroup>
</Target>

这完美地编译了协议缓冲区文件，并将它们添加到编译器的输入中（耶！）。但是，我想要包含 .pb.h 文件的其他源文件需要知道这些文件是在哪里生成的——该生成位置需要放在包含路径中。

因此，当且仅当用户在其脚本中的某处包含 <ProtocolBuffer 项目时，我想添加生成位置（在本例中为 $(ProtoOutPath) 到 ClCompile 的 <AdditionalIncludeDirectories>。

这可能吗，还是我需要让想要使用这些生成的位的 .cpp 文件跳过箍？

Answer 1

阅读您的问题并认为“不可能那么难”。伙计，我错了吗。首先我想只是给它一个条件，但是由于评估顺序，当然不能在顶级条件中使用 ItemGroups。然后我认为也不可能将 ItemDefinitionGroup 放在目标中（因为那里可以使用条件）并在那里修改它。然后我意识到这可能就是你问这个问题的原因后，我在键盘上敲了几次头

也许有一个更简单的解决方案，但最后我想：如果没有任何效果，我最喜欢的 msbuild 玩具又名 CodeTaskFactory 必须能够修复它。确实如此（我希望，没有完全测试结果），但这一点也不简单。在这里，请确保在 C++ 构建开始之前在某处调用测试目标。

<!--Uncomment the below to define some ProtocolBuffers-->  
<!--<ItemGroup>
  <ProtocolBuffer Include="Whitelist.proto" />
  <ProtocolBuffer Include="Whitelist2.proto" />
</ItemGroup>-->

<!--Suppose these are your default include files defined in your C++ project-->
<ItemDefinitionGroup Label="DefaultIncludes">
  <ClCompile>
    <AdditionalIncludeDirectories>/path/to/x;/path/to/y</AdditionalIncludeDirectories>
  </ClCompile>
</ItemDefinitionGroup>

<!--Include at least one item so we can play with it-->
<ItemGroup>
  <ClCompile Include="iamaninclude"/>
</ItemGroup>

<!--Use code to append to AdditionalIncludeDirectories-->
<UsingTask TaskName="AppendMetadata" TaskFactory="CodeTaskFactory" 
           AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll">
  <ParameterGroup>
    <Append ParameterType="System.String" Required="true"/>
    <ItemList ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true"/>
    <OutputItemList ParameterType="Microsoft.Build.Framework.ITaskItem[]" Output="true" />
  </ParameterGroup>
    <Task>
        <Code>
        <![CDATA[
            const string dirz = "AdditionalIncludeDirectories";
            foreach( var item in ItemList )
            {
              var cur = item.GetMetadata( dirz );
              item.SetMetadata( dirz, cur + ";" + Append );
            }
            OutputItemList = ItemList;
        ]]>
    </Code>
  </Task>
</UsingTask>

<!--Main target-->  
<Target Name="Test">
  <!--stage 1: copy the itemgroup, then clear it:
  if an Output TaskParameter is an Itemgroup, apparently the content
  gets appended to the group instead of replacing it.
  Found no documentation about this whatsoever though???-->
  <ItemGroup Condition="@(ProtocolBuffer) != ''">
    <ClCompileCopy Include="@(ClCompile)"/>
    <ClCompile Remove="@(ClCompile)"/>
  </ItemGroup>

  <!--stage 2: append 'ProtoBufIncludeDir' to AdditionalIncludeDirectories,
  and append the result to the origiginal again-->
  <AppendMetadata ItemList="@(ClCompileCopy)" Append="ProtoBufIncludeDir" Condition="@(ProtocolBuffer) != ''">
    <Output ItemName="ClCompile" TaskParameter="OutputItemList"/>
  </AppendMetadata>

  <!--stage 3: use modified itemgroup-->
  <Message Text="@(ClCompile->'%(Identity): %(AdditionalIncludeDirectories)')"/>
</Target>

打印出来

iamaninclude: /path/to/x;/path/to/y

除非 ProtocolBuffer 不为空，否则它会打印

iamaninclude: /path/to/x;/path/to/y;ProtoBufIncludeDir