Perf: Skip GetAttributes() for non-viable component properties

[ToddGrun]

During tag helper discovery, ComponentTagHelperProducer.GetProperties() calls GetAttributes() on every property to check for [Parameter]. This triggers expensive attribute binding and NullableWalker analysis in the Roslyn compiler for each call.

Properties that are private, static, indexers, or lack a public setter will always be Ignored regardless of attributes. For non-override properties, we can skip GetAttributes() entirely.

In Speedometer's RazorEditingTests.CompletionInCohostingForComponents, tag helper discovery re-runs on every keystroke because the source assembly symbol changes per compilation. The GetAttributes() calls contribute significantly to the 281MB of CLR_BytesAllocated_NonDevenv allocations in the devhub process — particularly NullableWalker (50MB+), BoundAttribute (13MB), and related binding infrastructure.

Override properties still go through GetAttributes() since [Parameter] determines shadow-vs-passthrough behavior.

[davidwengier]

For non-override properties, we can skip GetAttributes() entirely

I must be missing something about the original code, because I don't understand how this makes sense. Does that means [Parameter] public int Value {get;set;} will always be ignored because its not override? In the old code, the non-override properties were only ignored if they didn't have the attribute. BUT I must be wrong because none of the tests failed, and surely there is coverage for such a simple case. Maybe I need to have another coffee?

[ToddGrun]

Copilot wrote the comment, so if there's a way to clean that up to make more sense, just let me know and I'll change it.

However, logically, if any of these property conditions in the merged if are true, the code would have previously set kind to Ignored and then called the expensive GetAttributes method. Based on the results of that, it could have previously hit the continue if IsOverride was true, otherwise it would have always added to names/results. The check I added just says if IsOverride is false, then we know we wouldn't have hit the continue, and thus would have done the addition to names/results. So, thus we can skip the GetAttributes call.

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In reply to: 4309173208

[davidwengier]

🤦‍♂️. Thank you! Your reply pointed out what I was missing: The big red block of removed lines made me miss that the !IsOveride check is inside that merged if, so my example would have never hit there since the property is public.