Added singleflight and deterministic ordering.

[daveshanley]

smashing out non-deterministic issues once and for all, ordering maps and using singleflight and RWMutex.

[Copilot]

Pull request overview

This PR addresses non-deterministic behavior in reference extraction and resolution by introducing deterministic ordering through map key sorting, using singleflight for deduplication of concurrent lookups, and upgrading to RWMutex for better concurrency control.

• Implements deterministic ordering by sorting map keys before iteration across multiple index operations
• Adds singleflight pattern to deduplicate concurrent reference lookups and reduce contention
• Changes refLock from sync.Mutex to sync.RWMutex to allow concurrent reads

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
go.mod	Adds golang.org/x/sync v0.19.0 dependency for singleflight support
go.sum	Updates checksums for new golang.org/x/sync dependency
index/index_model.go	Changes refLock from sync.Mutex to sync.RWMutex for improved concurrency
index/spec_index.go	Sorts polymorphic reference map keys before iteration for deterministic ordering
index/resolver.go	Sorts component schemas and security schemes keys before iteration for deterministic ordering
index/extract_refs.go	Major refactoring: introduces singleflight for deduplication, channel-based collection for reduced mutex contention, position-based sorting for deterministic ordering, and adds locateRef helper function
index/determinism_benchmark_test.go	Adds regression tests and benchmarks to verify consistent deterministic ordering across multiple runs

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.59%. Comparing base (b4e5820) to head (94dfb0d).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #490      +/-   ##
==========================================
+ Coverage   99.58%   99.59%   +0.01%     
==========================================
  Files         175      175              
  Lines       21641    21700      +59     
==========================================
+ Hits        21552    21613      +61     
+ Misses         56       55       -1     
+ Partials       33       32       -1     

Flag	Coverage Δ
unittests	99.59% <100.00%> (+0.01%)	⬆️

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