Resolve Fusion abstract types via allocation-free ASCII byte lookup

[michaelstaib]

No description provided.

[Copilot]

Pull request overview

This pull request optimizes Fusion runtime type resolution by avoiding string materialization for __typename where possible, introducing UTF-8 span-based type lookup and an MRU memoization path for abstract type resolution.

Changes:

• Add FusionTypeDefinitionCollection overloads to resolve types from raw UTF-8 bytes (with FrozenDictionary alternate lookup on newer runtimes).
• Update execution-time abstract type resolution (ValueCompletion) to use AssertUtf8String() + MRU memoization and span-based schema lookup.
• Adjust/extend tests and add benchmarks to measure span-based type lookup and memoized abstract type resolution.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Text/Json/SourceResultDocumentTests.cs	Removes TryGetRawStringValue tests; should now cover AssertUtf8String.
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Execution/Types/FusionTypeDefinitionCollectionTests.cs	Adds tests for the new span-based type lookup APIs.
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Execution/Results/FetchResultStoreTests.cs	Adds regression coverage for abstract type fallback schema lookup when implementer count exceeds the lookup limit.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/UnionTests.cs	Updates expectations for escaped __typename handling in unions.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElementSnapshot.cs	Adds AssertUtf8String() to snapshot API and removes TryGetRawStringValue.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs	Adds AssertUtf8String() to element API and removes TryGetRawStringValue.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.Text.cs	Removes TryGetRawStringValue implementation from document text helpers.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/ValueCompletion.cs	Switches schema type to FusionSchemaDefinition, adds MRU memo, and uses UTF-8 span lookup for abstract type resolution.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/FetchResultStore.Pooling.cs	Updates initialization to use FusionSchemaDefinition.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/FetchResultStore.cs	Updates stored schema field type to FusionSchemaDefinition.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/OperationPlanContext.Pooling.cs	Casts request schema to FusionSchemaDefinition when initializing the result store.
src/HotChocolate/Fusion/src/Fusion.Execution.Types/Collections/FusionTypeDefinitionCollection.cs	Implements span-based GetType/TryGetType overloads with optimized NET9 alternate lookup.
src/HotChocolate/Fusion/benchmarks/Fusion.Execution.Benchmarks/SpanTypeLookupBenchmark.cs	Adds benchmark for span-based schema type lookup to validate allocation improvements.
src/HotChocolate/Fusion/benchmarks/Fusion.Execution.Benchmarks/AbstractTypeResolutionMemoBenchmark.cs	Updates benchmark to reflect AssertUtf8String + span-keyed lookup path.

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[github-actions]

Patch coverage

75.0% of changed lines covered (78/104)

File	Covered	Changed	Patch %
…/Fusion.Execution/Text/Json/SourceResultElementSnapshot.cs	0	6	0.0% 🔴
…/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs	4	6	66.7% 🔴
…/Collections/FusionTypeDefinitionCollection.cs	44	62	71.0% 🔴
…/Fusion.Execution/Execution/OperationPlanContext.Pooling.cs	1	1	100.0% 🟢
…/src/Fusion.Execution/Execution/Results/FetchResultStore.cs	1	1	100.0% 🟢
…/src/Fusion.Execution/Execution/Results/ValueCompletion.cs	28	28	100.0% 🟢

Uncovered changed lines (JSON)

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    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElementSnapshot.cs", "ranges": [[264, 267], [270, 271]] },
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs", "ranges": [[299, 300]] },
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution.Types/Collections/FusionTypeDefinitionCollection.cs", "ranges": [[17, 17], [180, 183], [196, 199], [209, 211], [248, 250], [269, 271]] }
  ]
}

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Project coverage: 53.8% (231911/430722 lines)