perf(execution): fast-path empty outcome calls

[thomhurst]

Summary

• bypass context rental and pipeline construction for ExecuteOutcomeAsync when the shield has no strategies
• preserve synchronous and asynchronous exception capture as Outcome<T>
• preserve cancellation and execution-metrics behavior

Profiling finding

ExecuteOutcomeAsync did not share the existing empty-pipeline fast path used by ExecuteAsync. A no-strategy outcome call therefore paid for KevlarContext.Rent, continuation construction, and context return on every execution.

Benchmark

BenchmarkDotNet 0.15.8, default job, .NET 10.0.11, Windows 11, Intel Core Ultra 9 185H. Both runs used the same checkout base and machine.

Benchmark	Before	After	Change	Allocated
Kevlar_EmptyOutcomeState	110.5 ns	21.28 ns	80.7% faster (5.2x)	0 B -> 0 B

Commands:

dotnet run --project benchmarks/Kevlar.Benchmarks -c Release --no-build -- --filter "*EmptyOutcomeState*"

Validation

• dotnet build Kevlar.slnx -c Release
• dotnet run --project tests/Kevlar.Tests -c Release --no-build -- --timeout 5m (612 passed)
• dotnet run --project tests/Kevlar.AllocationTests -c Release --no-build -- --timeout 5m (2 passed)

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of errors during direct actions so failures are returned consistently instead of causing unexpected interruptions.
  • Preserved successful results for both immediate and asynchronous actions.
  • Execution metrics are now recorded consistently for asynchronous processing.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 2262a0d6-d640-4ecf-8775-5bb931ab9458

📥 Commits

Reviewing files that changed from the base of the PR and between 86185a2 and 0d209b4.

📒 Files selected for processing (1)

• src/Kevlar/Internal/ShieldEngine.cs

Included review availability: Your plan provides up to 10 included reviews per hour; 3 remain after this review.

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📝 Walkthrough

Walkthrough

The direct-action execution path now converts synchronous exceptions, completed results, and asynchronous results into Outcome<T> values. Asynchronous handling also records success metrics.

Changes

Direct outcome handling

Layer / File(s)	Summary
Direct action execution and asynchronous conversion src/Kevlar/Internal/ShieldEngine.cs	ExecuteOutcomeAsync now handles synchronous results and exceptions as Outcome<T> values. Incomplete executions use AwaitDirectOutcomeAsync, which converts asynchronous results and exceptions and records success metrics.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 0d209

The change adds a localized fast path for empty outcome executions while preserving exception, cancellation, and metrics behavior; no actionable merge-blocking risk remains after normal checks and review.

Poem

I’m a rabbit in the code,
Hopping where direct actions go.
Errors turn to outcomes neat,
Async paths now land complete.
Metrics mark each success bright.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the fast path added for empty outcome calls in ExecuteOutcomeAsync.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf/outcome-fast-path

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