perf: Cache reflection in PipelineHost.DisposeAsync

[thomhurst]

Summary

• Cache the PropertyInfo lookup for the Disposables property using a ConcurrentDictionary<Type, PropertyInfo?> keyed by service provider type
• Avoids repeated reflection calls on every DisposeAsync invocation
• Uses static lambda to prevent closure allocation

Fixes #1473

Test plan

• Build passes (dotnet build)
• Existing tests continue to pass
• No behavior change, just performance improvement

🤖 Generated with Claude Code

[thomhurst]

Summary

Caches reflection lookup for the service provider's internal Disposables property to improve performance on repeated pipeline executions.

Critical Issues

None found ✅

Suggestions

Consider thread-safety of the cached PropertyInfo usage: While the ConcurrentDictionary safely caches the PropertyInfo lookup, the actual reflection access (GetValue(Services)) happens outside the cache. This is fine since PropertyInfo.GetValue is thread-safe, but it's worth noting that the Services instance could theoretically change between calls if service provider types differ across invocations.

Reflection on internal implementation details: This code relies on accessing a private "Disposables" property of the service provider implementation. While the caching improves performance, the underlying approach is fragile - if the Microsoft.Extensions.DependencyInjection internals change, this breaks. Consider:

• Is there a public API to enumerate disposables?
• Could this be handled through a custom service scope implementation instead?
• Worth adding a comment explaining why this reflection is necessary

These are minor observations - the caching implementation itself is solid and the static lambda prevents allocations as intended.

Verdict

✅ APPROVE - No critical issues, solid performance optimization

[Copilot]

Pull request overview

This PR introduces a performance optimization to the PipelineHost.DisposeAsync method by caching reflection lookups using a ConcurrentDictionary. The change avoids repeated reflection calls when accessing the internal Disposables property of the service provider.

Key changes:

• Added a static ConcurrentDictionary<Type, PropertyInfo?> to cache property reflection lookups
• Modified DisposeAsync to use GetOrAdd with a static lambda to retrieve cached PropertyInfo
• Extracted Services.GetType() call to a local variable to improve readability