如何从MSBuild目标修改ItemDefinitionGroup？

Question

我有一个用于编译Google Protocol Buffers文件的msbuild脚本:

<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>

这会完美地编译协议缓冲区文件,并将它们添加到编译器的输入中(是的!).但是,我想要包含.pb.h文件的其他源文件需要知道生成这些文件的位置 - 生成位置需要放在包含路径上.

因此,当且仅当用户<ProtocolBuffer在其脚本中的某处包含了一个项目时,我想添加生成位置(在本例中$(ProtoOutPath)为ClCompile的<AdditionalIncludeDirectories>.

这是可能的还是我需要制作想要使用这些生成的位跳过箍的.cpp文件？

Answer 1

阅读你的问题,并认为"不能那么难".伙计,我错了.首先我想只是给它一个条件,但当然由于评估顺序,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,在我意识到这可能是你提出这个问题的原因之后,我几次把头放在键盘上:(顺便说一句,你知道包含一个不存在的目录并不是真正的问题,因为编译器会高兴地忽略它吗？)

也许有一个更简单的解决方案,但最后我想:如果没有任何作用,我最喜欢的msbuild玩具又名CodeTaskFactory必须能够解决它.它确实(我希望,没有完全测试结果),但它根本不是直截了当的.在这里,确保在C++构建开始之前在某处调用Test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>

这打印

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

除非ProtocolBuffer不为空,否则它会打印出来

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