feat(configfileregistry): optimize config discovery

[camc314]

Refactor hot paths in project setup for better performance and simplicity.

• Config acquisition and parsing: Add fast-path for already-parsed configs, deduplicate concurrent parses using a wait group, use narrower locks (read locks for reads, write locks only for updates), avoid full reloads on entry creation, and support targeted reloads (file lists only).
• Default project discovery: Replace recursive goroutine-based traversal with a single-threaded iterative BFS queue. Track visited paths by (path, loadKind) pair, upgrade loadKind monotonically, and exit early on a good match. This removes recursion depth issues, goroutine overload, and sync overhead, while making resolution deterministic.
• Result tracking and service wiring: Use a single mutex with plain maps instead of SyncMaps and multiple locks. Ensure monotonic updates to prevent revisits with weaker loadKind. Initialize activeParsing in NewService and make cleanup consistent with BFS using plain maps under mutex.

These changes eliminate duplicate parsing, cut CPU spikes, and avoid goroutine storms in large reference graphs. The design now scales linearly with project size and offers more predictable latency under load.

Performance:

Old design: O(E) goroutines (E = edges in tsconfig graph), with duplicate work on converging paths. Parsing was O(N * c) worst-case (N = configs, c = concurrent requests per config).

New design: O(V + E) traversal (V = tsconfigs), visiting each config once per strongest loadKind. Parsing is O(N) amortized, as each config parses only once.

See oxc-project/tsgolint#99 for before/after analysis.

[Copilot]

Pull Request Overview

This PR refactors the configuration file discovery system to eliminate performance bottlenecks through several optimizations. The changes move from a concurrent goroutine-based approach to a deterministic iterative design that avoids duplicate work and scales linearly with project size.

Key changes include:

• Optimized config parsing: Fast-path for already-parsed configs, deduplication of concurrent parses using wait groups, and more granular locking
• Replaced recursive traversal: Single-threaded BFS queue instead of goroutine-based recursive search with better visited state tracking
• Simplified synchronization: Single mutex with plain maps replacing multiple sync.Map instances and separate locks

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
internal/project/configfileregistry.go	Adds deduplication logic for concurrent config parsing and fast-path returns for already-parsed configs
internal/project/defaultprojectfinder.go	Replaces recursive goroutine-based project discovery with iterative BFS queue and consolidated mutex usage
internal/project/service.go	Initializes activeParsing map and updates cleanup logic to use plain maps instead of sync.Map

---

_{You can also share your feedback on Copilot code review for a chance to win a $100 gift card. Take the survey.}

[jakebailey]

• Default project discovery: Replace recursive goroutine-based traversal with a single-threaded iterative BFS queue.

I suspect this may already be done in #1505 (or at least, a similar concept); a lot of this I think may end up changing in ways to make it work in snapshots.