Eliminate double-serialization in SystemTextJsonLanguageServer#83417
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ToddGrun wants to merge 1 commit intodotnet:mainfrom
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Eliminate double-serialization in SystemTextJsonLanguageServer#83417ToddGrun wants to merge 1 commit intodotnet:mainfrom
ToddGrun wants to merge 1 commit intodotnet:mainfrom
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SystemTextJsonDelegatingEntryPoint.ExecuteRequestAsync was calling JsonSerializer.SerializeToElement(result) to convert handler results into a JsonElement before returning to StreamJsonRpc. This caused a full serialize → byte[] → JsonDocument → JsonElement round-trip, only for StreamJsonRpc to immediately re-serialize that JsonElement back to wire bytes. Every LSP response paid this cost. The fix returns the handler's typed result directly as object. StreamJsonRpc serializes it to the wire using JsonSerializer.Serialize(writer, value, declaredType, options), which invokes the same runtime-type converters — producing identical JSON output with zero intermediate allocations. Why this is safe: The previous SerializeToElement(result, options) already received result as object (from InvokeAsync), so it was already relying on STJ's object→runtime-type dispatch. We're removing the redundant intermediate step, not changing the serialization path. The entry point methods are private, accessed only via MethodInfo name-based reflection — return type changes don't affect lookup. PIT impact: Identified via RazorEditingTests.CompletionInCohostingForComponents, scenario 0300.Completion. Eliminates ~12 MB of System.Byte[] and JsonDocument allocations in the devenv process from semantic tokens and completion responses.
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SystemTextJsonDelegatingEntryPoint.ExecuteRequestAsync was calling JsonSerializer.SerializeToElement(result) to convert handler results into a JsonElement before returning to StreamJsonRpc. This caused a full serialize → byte[] → JsonDocument → JsonElement round-trip, only for StreamJsonRpc to immediately re-serialize that JsonElement back to wire bytes. Every LSP response paid this cost.
The fix returns the handler's typed result directly as object. StreamJsonRpc serializes it to the wire using JsonSerializer.Serialize(writer, value, declaredType, options), which invokes the same runtime-type converters — producing identical JSON output with zero intermediate allocations.
Why this is safe: The previous SerializeToElement(result, options) already received result as object (from InvokeAsync), so it was already relying on STJ's object→runtime-type dispatch. We're removing the redundant intermediate step, not changing the serialization path. The entry point methods are private, accessed only via MethodInfo name-based reflection — return type changes don't affect lookup.
PIT impact: Identified via RazorEditingTests.CompletionInCohostingForComponents, scenario 0300.Completion. Eliminates ~12 MB of System.Byte[] and JsonDocument allocations in the devenv process from semantic tokens and completion responses.
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Microsoft Reviewers: Open in CodeFlow