[glen-84]

Summary

• SchemaValidator resolves the handler set for each event type once per validator, instead of type-testing every rule against every published event. Validating the GitHub public schema publishes 49,899 events, so the old linear scan performed roughly 898,000 interface type tests per validation.
• Validation events are now readonly record struct, so publishing an event no longer allocates. This requires IValidationEventHandler<TEvent> to drop its in variance, which value types cannot satisfy. Both changes are breaking for anyone implementing custom rules outside this repository.
• ValidNameRule compares the __ prefix ordinally rather than culture-sensitively, and ValidImplementationsRule builds its log-entry lists only when it has something to report and resolves implemented arguments by name instead of building a dictionary per field.
• Against the GitHub public schema (1,813 types), validation goes from 4,013 μs and 2,109 KB to 1,347 μs and 520 KB, which is below the schema-build validator's 736 KB.

Test plan

• dotnet test src/HotChocolate/Core/test/Types.Validation.Tests — 129 passing
• dotnet test src/HotChocolate/Fusion/test/Fusion.Composition.Tests — 712 passing, exercising the mutable-schema consumer
• BenchmarkDotNet comparison against the GitHub public schema, with per-rule and rule-count ablation runs to attribute each change

[Copilot]

Pull request overview

This PR optimizes HotChocolate schema validation by reducing per-event rule scanning and eliminating validation-event allocations, aiming to lower both runtime and GC pressure during schema builds.

Changes:

• Cache the handler set per validation event type per SchemaValidator instance to avoid repeated is/OfType scanning for every published event.
• Convert validation events from sealed record to readonly record struct and adjust IValidationEventHandler<TEvent> to remove contravariance to support struct events.
• Micro-optimizations in validation rules (ordinal __ prefix check; reduce allocations in interface implementation validation).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/HotChocolate/Core/src/Types.Validation/SchemaValidator.cs	Caches per-event handler arrays to avoid re-scanning all rules for each published validation event.
src/HotChocolate/Core/src/Types.Validation/Rules/ValidNameRule.cs	Uses ordinal comparison for reserved-name detection to avoid culture-sensitive overhead.
src/HotChocolate/Core/src/Types.Validation/Rules/ValidImplementationsRule.cs	Avoids allocating error lists and argument dictionaries unless needed during interface-implementation checks.
src/HotChocolate/Core/src/Types.Validation/Events/ValidationEvents.cs	Converts validation events to readonly record struct to eliminate per-event allocations.
src/HotChocolate/Core/src/Types.Validation/Events/Contracts/IValidationEventHandler.cs	Removes in variance to align with struct-based events and updated dispatch.

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[github-actions]

Patch coverage

95.1% of changed lines covered (58/61)

File	Covered	Changed	Patch %
…/Core/src/Types.Validation/Events/ValidationEvents.cs	13	16	81.3% 🟡
…/Core/src/Types.Validation/Rules/ValidImplementationsRule.cs	21	21	100.0% 🟢
…/Core/src/Types.Validation/Rules/ValidNameRule.cs	1	1	100.0% 🟢
…/HotChocolate/Core/src/Types.Validation/SchemaValidator.cs	23	23	100.0% 🟢

Uncovered changed lines (JSON)

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  "files": [
    { "path": "src/HotChocolate/Core/src/Types.Validation/Events/ValidationEvents.cs", "ranges": [[60, 60], [105, 105], [110, 110]] }
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Project coverage: 53.9% (232774/431566 lines)