Well-known metadata not available when dynamically creating items

[nickwalkmsft]

Well-known item metadata is not available during item creation for dynamically defined items (items defined within a Target). I am not super familiar with msbuild but this was surprising to me.

Steps to reproduce

Project file

<Project>

    <!-- Regular ol' items containing metadata defined from well-known metadata. %(Filename) and other
         well-known metadata exist during creation, so ArbitraryMetadata is defined with the value of
         Filename as expected -->
    <ItemGroup>
        <MyFileItems Include="myfiles\*" ArbitraryMetadata="%(Filename)" />
    </ItemGroup>

    <Target Name="MyTarget">

        <!-- Works as expected -->
        <Message Importance="high" Text="%(MyFileItems.Identity) -> %(MyFileItems.ArbitraryMetadata)" />

        <!-- Now dynamically (within the Target) define another item list the same way -->
        <ItemGroup>
            <MyDynamicFileItems Include="myfiles\*" ArbitraryMetadata="%(Filename)" />
        </ItemGroup>

        <!-- Unexpected: ArbitraryMetdata is empty, because %(Filename) and all other well-known metadata
             was not defined during creation -->
        <Message Importance="high" Text="%(MyDynamicFileItems.Identity) -> %(MyDynamicFileItems.ArbitraryMetadata)" />

        <!-- Note that %(Filename) and other well-known metadata *is* available now that the item list has
             already been created -->
         <Message Importance="high" Text="%(MyDynamicFileItems.Identity) -> %(MyDynamicFileItems.Filename)" />
    </Target>

</Project>

Directory contents:

/
- repro.proj
- myfiles/
     - file1
     - file2
     - file3

Command line

msbuild repro.proj /t:MyTarget

Expected behavior

Prints:

  myfiles\file1 -> file1
  myfiles\file2 -> file2
  myfiles\file3 -> file3
  myfiles\file1 -> file1
  myfiles\file2 -> file2
  myfiles\file3 -> file3
  myfiles\file1 -> file1
  myfiles\file2 -> file2
  myfiles\file3 -> file3

Actual behavior

Prints:

  myfiles\file1 -> file1
  myfiles\file2 -> file2
  myfiles\file3 -> file3
  myfiles\file1 -> 
  myfiles\file2 -> 
  myfiles\file3 -> 
  myfiles\file1 -> file1
  myfiles\file2 -> file2
  myfiles\file3 -> file3

Environment data

msbuild /version output:

Microsoft (R) Build Engine version 15.4.8.50001 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

15.4.8.50001

OS info:
Microsoft Windows [Version 10.0.16299.192]

If applicable, version of the tool that invokes MSBuild (Visual Studio, dotnet CLI, etc):

I'm seeing this behavior everywhere - VS, dotnet, running msbuild manually.

[manio143]

I've encountered this today when creating a target which would include content created in a previous target.
The Filename metadata was not available within the item group definition but it was available in the step right after.

Not working

<Target Name="IncludeFrontendDist" AfterTargets="YarnBuild">
  <ItemGroup>
    <Content Include="$(SolutionDir)/../frontend/dist/*">
      <TargetPath>wwwroot/%(Filename)%(Extension)</TargetPath>
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
  </ItemGroup>
</Target>

Working

<Target Name="IncludeFrontendDist" AfterTargets="YarnBuild">
  <ItemGroup>
    <FrontendFiles Include="$(SolutionDir)/../frontend/dist/*" />
    <Content Include="@(FrontendFiles)">
      <TargetPath>wwwroot/%(FrontendFiles.Filename)%(FrontendFiles.Extension)</TargetPath>
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
  </ItemGroup>
</Target>

Moreover, due to this being an ASP.NET Core application with some Razor content, the error message was very confusing, because it was pulling Filename property from previously defined Content items.

Two assets found targeting the same path with incompatible asset kinds:
'..\frontend\dist\file1.js' with kind 'All'
'..\frontend\dist\file2.js' with kind 'All'
for path 'PreviouslyInContent.cshtml'

[KalleOlaviNiemitalo]

There was a warning added in #8581. Does that trigger in your scenario?

[manio143]

No, the warning was not shown. My MSBuild version (SDK 7.0.302) 17.6.1+8ffc3fe3d
That PR will make it into the next SDK release I think.