OpenAPI XML source generator "slow"

[martincostello]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

From anecdotal usage of building a number of my OSS projects with .NET 10 preview 2 with the new OpenAPI XML source generator enabled, it feels like the build times have increased by double digit number of seconds.

Exact numbers at this stage are hard to quantity as issues in preview 2 (#61019, #61035, #61037, #61042) prevent me from successfully compiling these projects with the generator enabled, so it may be that the perf impact on build times is related to the errors being emitted, but the build feels slower when watching the SDK do its thing in a terminal window for dotnet build.

Discussed this with @captainsafia earlier and she said filing an issue on "vibes" was fine as a starting point for a more detailed investigation into any performance improvements that could be made to the source generator.

PRs for .NET 10 where I've tried out the source generator:

• Update to .NET 10 martincostello/adventofcode#2106
• Update to .NET 10 martincostello/alexa-london-travel-site#3114
• Update to .NET 10 martincostello/api#2207
• Update to .NET 10 martincostello/openapi-extensions#264

Expected Behavior

Compile times for projects are not perceptibly impacted when the OpenAPI XML documentation source generator runs.

Steps To Reproduce

Nothing concrete yet due to the referenced issues blocking successful compilation.

Exceptions (if any)

No response

.NET Version

10.0.100-preview.2.25164.34

Anything else?

No response