User Story: Source generators are added to common libraries to improve performance

[samsp-msft]

Source Generators are a new technology that was added to Roslyn in the .NET 5 timeframe, but we have not yet utilized them by creating generators to assist with runtime and framework features. We will work to define customer scenarios in more detail here with customer development.

Code that uses runtime reflection and reflection.emit causes issues for Trimming and Native AOT. Source generators can be used to generate alternative code at build time that is static so can be used in conjunction with Trimming and AOT. Work on trimming ASP.NET apps has revealed where there are current limitations that can be solved by source generators.

[YairHalberstadt]

Trimming / Blazor / Native & Mono AOT – source generators can be used to convert code that does reflection.emit at runtime to source generators which will create code at build time rather than runtime. The generated code can then be analyzed by the illinker or native AOT enabling those scenarios.
Dependency Injection – is an important part of ASP.NET startup that could be replaceable with code generation at build time.

I have a project which does DI entirely at compile time via source generators: https://github.com/YairHalberstadt/stronginject

It's ideal for use cases which want to avoid any reflection, so great for trimming, blazor, and AOT. It's not a drop in replacement for Asp.Net DI, but maybe might serve as some inspiration.

There's plenty of other open source projects using source generators for things like serialization, and other reflection usages. I think it would be awesome if Microsoft could help with spreading the word about these projects, and possibly contributing, rather than creating competing alternatives!

Thanks for all the good work!

[danmoseley]

Any community feedback on @samsp-msft prioritization above?

[richlander]

I'd like to see the BCL and ASP.NET options prioritized separately. I don't think its useful to stack rank those together.

[danmoseley]

@samsp-msft We should break these into separate user stories, probably one per source ge erator -- as they need to be costed, prioritized, owned separately. Can we do that?.