Warning in MAUI when referencing a project with GenerateDocumentationFile true

[mattjohnsonpint]

Description

If you create a project reference from a MAUI project to a class library, and that project is generating XML documentation files, you get the following build warnings - two for each reference (one for iOS, one for maccatalyst):

Xamarin.Shared.Sdk.targets(1439, 3): The file '/Users/matt/Code/MyMauiApp/ClassLibrary1/bin/Debug/net6.0/ClassLibrary1.xml' does not specify a 'PublishFolderType' metadata, and a default value could not be calculated. The file will not be copied to the app bundle.
Xamarin.Shared.Sdk.targets(1439, 3): The file '/Users/matt/Code/MyMauiApp/ClassLibrary1/bin/Debug/net6.0/ClassLibrary1.xml' does not specify a 'PublishFolderType' metadata, and a default value could not be calculated. The file will not be copied to the app bundle.

Steps to Reproduce

1. Create a new MAUI app (dotnet new maui, etc.)
2. Add a class library project to the same solution
3. Put some XML summary comments on the public members in that class library project.
4. Set <GenerateDocumentationFile>true</GenerateDocumentationFile> (per this) in the csproj for the class library project
5. Reference the class library project from the MAUI app.
6. Compile and see the warnings

Version with bug

Release Candidate 3 (current)

Last version that worked well

Unknown/Other

Affected platforms

iOS, macOS

Affected platform versions

any

Did you find any workaround?

I think this may be related or similar to xamarin/xamarin-macios#14939, but the workaround there did not work for me, and I'm not sure if this is MAUI specific or not.

Relevant log output

No response

[VincentBu]

repro with vs main build(32522.39.main)

[mattjohnsonpint]

I've created a workaround. Add this to the .csproj of the app (or place in a custom .targets file, etc.):

  <!-- Workaround for https://github.com/dotnet/maui/issues/7272 -->
  <Target Name="_SetPublishFolderTypeNoneOnDocFileItems" BeforeTargets="_ComputePublishLocation">
    <ItemGroup>
      <ResolvedFileToPublish Update="@(DocFileItem)" PublishFolderType="None" />
    </ItemGroup>
  </Target>

That will set the PublishFolderType metadata to None on all DocFileItem items (the generated XML doc files), and prevent the warning. (ResolvedFileToPublish is the list that the ComputeBundleLocation task uses, within the _ComputePublishLocation target, so updating it before that runs takes care of this.)

I believe something like this should be done somewhere in Xamarin.Shared.Sdk.targets for a permanent fix, but perhaps somewhere else is more appropriate.

[mattjohnsonpint]

Just an update, My workaround above did remove the warning, but it also broke everything because I was mistaken in thinking @(DocFileItem) will still be available. It's not. Here's one that actually works.

  <!-- Workaround for https://github.com/dotnet/maui/issues/7272 -->
  <Target Name="_SetPublishFolderTypeNoneOnDocFileItems" BeforeTargets="_ComputePublishLocation">
    <ItemGroup>
      <ResolvedFileToPublish
        Update="@(ResolvedFileToPublish)"
        Condition="'%(ResolvedFileToPublish.Extension)' == '.xml' And '%(ResolvedFileToPublish.PublishFolderType)' == ''"
        PublishFolderType="None" />
    </ItemGroup>
  </Target>

Though, it does presume that any .xml file that doesn't have a PublishFolderType set already must have it set to None. Is there a better way to know if a file was a generated doc file, at this point in the build process?

[mattjohnsonpint]

FYI, this happens not just on MAUI, but also with an app made via dotnet new ios. Should I close this and open a new issue on https://github.com/xamarin/xamarin-macios?

[jfversluis]

If it also happens on iOS without .NET MAUI involved then yes please move it there. Thanks!