Switched resolver and execution logic to voption

[xperiandri]

Summary

Continues the ongoing struct-optionals effort by moving the resolver and execution pipeline from reference option to struct voption, removing allocations on the hottest path of query execution.

This is a focused follow-up to the already-merged active-pattern conversion (#610) and is orthogonal to the optional-parameter work in #604 — reviewers of those PRs do not need to re-review that ground here.

What changed

Execution pipeline (src/FSharp.Data.GraphQL.Server/Execution.fs)

• ResolverResult<'T> now carries IObservable<GQLDeferredResponseContent> voption instead of option.
• executeResolvers accepts AsyncVal<obj voption> instead of AsyncVal<obj option>.
• Pattern matches and call sites updated to ValueSome / ValueNone.
• Deferred/streamed resolver plumbing threads voption end-to-end, so no boxing round-trip remains between the resolver and the response writer.

Shared helpers

• Extensions.fs: new ValueOption.mergeWith and ValueOption.unwrap, mirroring the existing Option counterparts.
• ObjAndStructConversions.fs: added Array.vtryPick.
• Reflection.fs: objectOptionCast is now accessible and documented; new toValueOption lifts an obj into obj voption unless it is already an option; the now-unused optionCast wrapper was dropped.

Client

• BaseTypes.fs, GraphQLClient.fs, ReflectionPatterns.fs, Serialization.fs updated to the voption-based helpers, plus assorted string-formatting and XML-doc cleanups.

Compatibility notes

• ResolverResult<'T> is public and its shape changed (option -> voption). Code that destructures it directly needs a mechanical Some/None -> ValueSome/ValueNone update.
• Reflection.optionCast was removed; objectOptionCast (returning voption) is the replacement, and ValueOption.toOption recovers the old shape if needed.

Validation

• dotnet build FSharp.Data.GraphQL.slnx — 0 errors, 0 warnings.
• dotnet test tests/FSharp.Data.GraphQL.Tests — 667 passed, 0 failed, 5 skipped.

Related

• Use struct-returning partial active patterns #610 — struct active patterns (merged)
• Use [<Struct>] ? optional parameters and voption in Define/DefineRec and the introspection chain #604 — struct optional parameters (open, independent)

[github-actions]

Test Results

    9 files      9 suites   13m 5s ⏱️
  777 tests   772 ✅  5 💤 0 ❌
2 331 runs  2 316 ✅ 15 💤 0 ❌

Results for commit a965a9e.

♻️ This comment has been updated with latest results.

[Copilot]

Copilot review overview

🟡 Changes recommended

toValueOption incorrectly wraps boxed ValueNone values as present values, breaking nullable voption list elements.

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Review effort: Lite
Findings: 1

Open (1)

• Boxed ValueNone is incorrectly wrapped as ValueSome · New

What changed in this PR

Moves resolver execution and client serialization from reference option to struct voption.

Changes:

• Adds shared ValueOption and collection helpers.
• Updates server execution, deferred, streamed, and live resolver paths.
• Adapts client reflection, serialization, and upload handling.

File	Description
Validation.fs	Uses struct-option lookup helpers.
Reflection.fs	Adds object-to-voption conversion.
ObjAndStructConversions.fs	Consolidates option helpers.
Extensions.fs	Removes relocated helpers.
CollectionExtensions.fs	Adds collection voption helpers.
FSharp.Data.GraphQL.Shared.fsproj	Includes the new helper file.
Execution.fs	Threads voption through execution.
Serialization.fs	Handles struct-option client values.
ReflectionPatterns.fs	Adds struct-option reflection patterns.
GraphQLClient.fs	Updates upload traversal.
BaseTypes.fs	Uses struct-option conversions.

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[Copilot]

Copilot review overview

🔵 Needs a closer look

The list lookup helper introduces sequence/enumerator allocations on an execution path targeted for allocation reduction.

Review effort: Lite
Findings: None

Resolved since last review (1)

• Boxed ValueNone is incorrectly wrapped as ValueSome

Previously missed (1)

In code that hasn't changed since last review

Avoid lazy Seq allocation in voption list lookup

src/​FSharp.Data.GraphQL.Shared/​Helpers/​CollectionExtensions.fs:78

This helper is now used by the execution path (Execution.fs:44), but implementing it through Seq.where and Seq.vtryHead creates a lazy sequence/enumerator for every list lookup. That can allocate more than the previous List.tryFind and undermines the PR's allocation-reduction goal; implement the voption lookup with a direct tail-recursive loop over the list instead.