feat: use valueTask for the feed iterator's MoveNextAsync

[xperiandri]

Proposed Changes

The first use of IcedTasks in library code. #40, now merged, added IcedTasks 0.11.10-beta001 and the tests that check its builders in Debug and Release (the probes); every probe of valueTask, valueTaskUnit, cancellableTask and cancellableValueTask passes, so the gate in .github/copilot-instructions.md allows these builders.

• feat: use valueTask for the feed iterator's MoveNextAsync: FeedIteratorAsyncEnumerator.MoveNextAsync built a Task with task { } and wrapped it in a ValueTask<bool>, a hand-rolled wrapper the coding guidelines forbid. It now uses valueTask { } around the same loop. The enumerator itself stays hand-written, because taskSeq still has no dynamic implementation. The XML documentation of MoveNextAsync says why this is safe in Debug builds. The package now depends on IcedTasks (>= 0.11.10-beta001), recorded in the CHANGELOG.
• refactor: use valueTaskUnit for the test fixture's DisposeAsync: the task { } |> ValueTask wrapper in DisposeAsync of tests/Cosmos.Tests.Infrastructure becomes valueTaskUnit { }. The infrastructure project references IcedTasks directly.
• docs: reference taskSeq through see cref in the feed iterator docs: the documentation of FeedIteratorAsyncEnumerator and of FeedIteratorAsyncEnumerable.GetAsyncEnumerator named the taskSeq builder in <c> tags and the token type in plain words; it now refers to both through <see cref>, as the rest of the file does.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Internal change; the public API is unchanged. The package gains the IcedTasks dependency.

Checklist

• Build and tests pass locally
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

Further comments

• Behaviour: a check harness compared the old task wrapper, the new valueTask version and the built library over these cases, in Debug and Release:

  • several pages and empty pages;
  • asynchronously completing and pending pages;
  • 100,000 empty pages;
  • cancellation before, during and between pages;
  • failing reads;
  • double dispose.

  All transcripts were identical, and allocation per synchronously completing call is unchanged.

• Tests without the emulator on the current head (category Unit, all 30 probes included): Debug 77/77 and Release 77/77. The full emulator suite last ran before the latest rebase and documentation changes, at the default parallelism: Debug 185/185 and Release 185/185, none skipped; the library and test-infrastructure code it ran are unchanged since. Every commit builds in Release with the same 19 warnings as main; Fantomas is clean.

• dotnet pack reports NU5104: a stable package should not depend on the prerelease IcedTasks 0.11.10-beta001. It is a warning, and CI packages are prereleases themselves. A stable release of this package should wait for IcedTasks 0.11.10 stable.

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused implementation preserves behavior, follows project guidance, and is covered by existing iterator and builder probes.

Review effort: Balanced
Findings: None

What changed in this PR

Replaces the feed iterator’s hand-built Task-wrapped ValueTask with the approved IcedTasks valueTask computation expression.

Changes:

• Uses valueTask in MoveNextAsync.
• Adds IcedTasks as a library dependency.
• Documents builder-specific safety requirements and the dependency change.

File	Description
.github/​copilot-instructions.md	Defines builder-specific IcedTasks usage gates.
CHANGELOG.md	Records the new dependency and implementation change.
src/​Cosmos/​FSharp.Azure.Cosmos.fsproj	Adds the IcedTasks package reference.
src/​Cosmos/​IterationExtensions.fs	Converts MoveNextAsync to valueTask.
tests/​Cosmos.Tests/​FSharp.Azure.Cosmos.Tests.fsproj	Clarifies the direct probe-test dependency.

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[Copilot]

🟢 Approval recommended

The focused refactor follows project guidance and is supported by existing iterator tests and builder probes.

0 open findings

🧠 Review effort: Balanced