Bug: CppWinRTCopyWinMDToOutputDirectory: Outputs mismatch when merged WinMD name differs from RootNamespace

[SnarkyCarbivore]

Version

2.0.220131.2

Summary

Problem

The CppWinRTCopyWinMDToOutputDirectory target has mismatched Inputs/Outputs:

• Inputs: @(_MdMergedOutput) — the merged WinMD (e.g. Contoso.Core.winmd)
• Outputs: $(CppWinRTProjectWinMD) — resolves to $(OutDir)$(RootNamespace).winmd (e.g. Contoso.App.winmd)
• Copy DestinationFiles: @(_MdMergedOutput->'$(OutDir)%(Filename)%(Extension)') — writes the correct file

When the merged WinMD filename differs from $(RootNamespace), the declared Output never matches the actual file written. MSBuild always considers the target out-of-date, causing cascading rebuilds in all downstream projects (.xbf copies, PRI regen, MSIX packaging, C# recompiles via CsWinRT).

This happens when a project's IDL files use a different root namespace than the project's RootNamespace property (e.g. IDL uses Contoso.Core but the project's RootNamespace is Contoso.App).

Fix

Change Outputs to a 1:1 transform matching the Copy task:

Outputs="@(_MdMergedOutput->'$(OutDir)%(Filename)%(Extension)')"

Also update FileWrites to match

Reproducible example

Expected behavior

No response

Actual behavior

No response

Additional comments

No response

[YexuanXiao]

2.0.220131.2 is a very old version, you should try updating to the latest version.

[SnarkyCarbivore]

Checked 2.0.250303.1 — the CppWinRTCopyWinMDToOutputDirectory target definition is identical to 2.0.220131.2. The Outputs still uses $(CppWinRTProjectWinMD) while Copy DestinationFiles uses the @(_MdMergedOutput) transform.