Dotnet 10 requires interceptors feature

[rouke-broersma]

1. .NET 10 now has interceptors enabled by default.
2. ASP.NET 10 Core features like AddOpenApi/MapOpenApi and Minimal API Validation use interceptors for their purposes.
3. Stryker uses Roslyn 4.14 where interceptors are disabled by default.
4. ASSUMPTION: The authors of Stryker need to opt-in to use interceptors, otherwise anything Stryker attempts to recompile, if it uses interceptors, will fail to compile with "CS9137, message: The 'interceptors' feature is not enabled in this namespace."

Originally posted by @aannenko in #3379 (comment)

[rouke-broersma]

We most likely need to enable a roslyn compiler feature for this. We need to determine if this can safely be enabled by default for dotnet 8-10. We also need to determine if this needs to be configurable by users.

[dupdob]

I am still trying to figure out how the interception location is defined. Anyway, it looks like mutating code containing intercepted method(s) will create a lot of 'interesting' situations 😱.

[rouke-broersma]

It looks like consumers do need to explicitly opt in to interceptors in their source project using the interceptors namespaces msbuild property. We need to capture this msbuild property and it looks like we need to pass it into CSharpParseOptions.WithFeatures(...)

We also need to capture InterceptorsPreviewNamespaces

Source: https://stackoverflow.com/questions/79816934/microsoft-aspnetcore-openapi-10-0-0-the-interceptors-feature-is-not-enabled

dotnet/roslyn#70935

Since users need to explicitly opt in anyway by setting the msbuild property this seems pretty safe to add in that regard. In regards to what it does to syntax trees? I don't even want to think about that yet 🫣

[rouke-broersma]

We should also add an integration test. Create a new target project using dotnet new webapi and ensuring interceptors are enabled. Replace one of the current integration target projects with this, copy the existing content into the new project, avoids adding more runtime. First change the integration test, confirm that it's failing, then imply the fix, confirm it's working.

[dupdob]

I am still trying to figure out how the interception location is defined. Anyway, it looks like mutating code containing intercepted method(s) will create a lot of 'interesting' situations 😱.

I realize interception is typically by source generator that will process the files after the mutation. This would only be an issue when interception is done manually. But interception location description does not appear to be documented...
overall this feature still feel half backed