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Diagnostics

Preview OpenAPI XmlComments Reviewed 2026-11-03 purview-dev/openapi-xmlcomments Star on GitHub agent-skills aspnetcore build-tooling csharp dotnet msbuild nuget openapi source-generator xml-comments xml-documentation

Diagnostics

Section titled “Diagnostics”

POAX001

Section titled “POAX001”
warning POAX001: 'T:Ambient.InjectedAttribute' is documented both in this project and in Lib.A.xml. If this
project's copy is public, the OpenAPI XML-comment cache throws "An item with the same key has already been added" at
run time; add <PurviewOpenAPIXmlCommentExclude Include="T:Ambient.InjectedAttribute" /> to drop the reference's copy.

Cause. The ID is documented in the API project itself and in exactly one referenced project. It is not a duplicate among the referenced documentation, so it was not removed before compile, but the generator also adds the API’s own public documented symbols, so it will collide.

Fix. Add the item the warning names to the API project:

<ItemGroup>
  <PurviewOpenAPIXmlCommentExclude Include="T:Ambient.InjectedAttribute" />
</ItemGroup>

The overlap is only visible after the API compiles, so the exclude takes effect on the next build.

False positives. The generator only reads the API’s public symbols, so an overlap with an internal type in the API does not fail. The warning cannot tell the two apart from the documentation file; silence it with MSBuildWarningsAsMessages if it is one of those (see Configuration).