Refactor param binding failure handling in RequestDelegate

[marcominerva]

Description

Refactor RequestDelegateFactory to handle parameter binding failures more flexibly:

• Execute filter pipelines on failure if filters are present and return type is ValueTask<object?>, allowing filters to observe/modify the 400 response.
• Short-circuit with a 400 response if no filters are present.
• Simplify logic using Expression.Condition and Expression.Block.

Add new test cases in RouteHandlerEndpointRouteBuilderExtensionsTest.cs:

• Validate behavior with/without filters and custom responses.
• Ensure handlers are not executed on binding failure.

Fixes #64341

[Copilot]

Pull request overview

This pull request refactors parameter binding failure handling in RequestDelegateFactory to provide more flexible filter integration. The key change allows endpoint filters to observe and potentially customize 400 Bad Request responses when parameter binding fails, rather than always short-circuiting before filters run.

Key Changes:

• Unified the parameter binding failure logic using Expression.Condition instead of separate code paths for filtered vs non-filtered scenarios
• When filters are present and return type is ValueTask<object?>, the filter pipeline executes on binding failure, allowing filters to customize the 400 response
• Added comprehensive test coverage for binding failure scenarios with and without filters

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Http/Http.Extensions/src/RequestDelegateFactory.cs	Refactored CreateParamCheckingResponseWritingMethodCall to conditionally run filter pipelines on parameter binding failures, simplifying the code with a unified Expression.Condition approach
src/Http/Routing/test/UnitTests/Builder/RouteHandlerEndpointRouteBuilderExtensionsTest.cs	Added 4 test cases validating parameter binding failure behavior: with/without filters, with custom filter responses, and with validation filters