MAUI Xaml SourceGen breaks when nullable is enabled and <WarningsAsErrors>Nullable</WarningsAsErrors> is set

[Jakar510]

Description

MAUI Xaml SourceGen breaks when nullable is enabled and <WarningsAsErrors>Nullable</WarningsAsErrors> is set in the csproj.

Steps to Reproduce

Setup your csproj something like:

<TargetFrameworks>net10.0-android;net10.0-ios;net10.0-maccatalyst</TargetFrameworks> <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net10.0-windows10.0.19041.0</TargetFrameworks> <!-- Uncomment to also build the tizen app. You will need to install tizen by following this: https://github.com/Samsung/Tizen.NET --> <!-- <TargetFrameworks>$(TargetFrameworks);net10.0-tizen</TargetFrameworks> --> <UseMaui>true</UseMaui> <SingleProject>true</SingleProject> <ImplicitUsings>enable</ImplicitUsings> <Nullable>enable</Nullable> <AllowUnsafeBlocks>true</AllowUnsafeBlocks> <GeneratedFolder>Generated</GeneratedFolder> <MauiXamlInflator>SourceGen</MauiXamlInflator> <!-- <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles> --> <!-- <CompilerGeneratedFilesOutputPath>Generated</CompilerGeneratedFilesOutputPath> --> <MauiEnableXamlCBindingWithSourceCompilation>true</MauiEnableXamlCBindingWithSourceCompilation> <NoWarn>$(NoWarn);1701;1702;1591;IDE0079;IDE0046;CA2208;IL2121;CS1573;CS1591;CA1416</NoWarn> <WarningsAsErrors>Nullable;CS0114;CS0108</WarningsAsErrors> <AllowUnsafeBlocks>True</AllowUnsafeBlocks>

Try to run the build in release. debug has issues too but sometimes still builds and runs.

Link to public reproduction project repository

No response

Version with bug

10.0.11

Is this a regression from previous behavior?

No, this is something new

Last version that worked well

No response

Affected platforms

iOS, Android

Affected platform versions

iOS 26.1 / Android 16

Did you find any workaround?

Disable <WarningsAsErrors>Nullable</WarningsAsErrors>

Relevant log output

[StephaneDelcroix]

We have <TreatWarningsAsErrors>true</TreatWarningsAsErrors> on all our projects and tests and never experienced that. Could you please provide a really simple sample project we could use ?

[Jakar510]

I'll look into it

[dotnet-policy-service]

Hi @@Jakar510. We have added the "s/needs-repro" label to this issue, which indicates that we require steps and sample code to reproduce the issue before we can take further action. Please try to create a minimal sample project/solution or code samples which reproduce the issue, ideally as a GitHub repo that we can clone. See more details about creating repros here: https://github.com/dotnet/maui/blob/main/.github/repro.md

This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[dotnet-policy-service]

Hi @@Jakar510. We have added the "s/needs-info" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.