Genericize ref counting caches; fix extended config cache bug

[andrewbranch]

I plan to add another one of these shared caches for parsed package.json files for the auto-imports work, so I went ahead and made the implementation generic, which required some fiddling with config file parsing to not pass a closure on every cache lookup so we don’t also pass a closure on every source file lookup. I also noticed a bug with the extended config caching, which is covered in a new test and fixed.

[Copilot]

Pull request overview

This PR refactors the reference counting cache implementations into a generic RefCountCache type and fixes a bug with extended config file caching. The key changes eliminate closure-based cache lookups, replacing them with direct function calls and structured arguments.

• Introduces a generic RefCountCache implementation that can be specialized for different cache types
• Fixes extended config cache bug where doubly-nested extended configs weren't being invalidated properly
• Updates ParseCacheKey to include file hash as part of the key identity

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/project/refcountcache.go	New generic reference counting cache implementation with support for expiration checks and configurable deletion
internal/project/parsecache.go	Refactored to use generic RefCountCache; hash now part of cache key
internal/project/extendedconfigcache.go	Refactored to use generic RefCountCache with hash-based expiration detection
internal/project/configfileregistrybuilder.go	Fixed bug where oldCommandLine was not saved before reload, preventing proper extended config invalidation; updated GetExtendedConfig signature
internal/tsoptions/tsconfigparsing.go	Exported ParseExtendedConfig function; updated ExtendedConfigCache interface to pass parameters directly instead of via closure; changed ExtendedSourceFiles to use InsertSorted for deterministic ordering
internal/tsoptions/tsconfigparsing_test.go	Updated test mock to match new ExtendedConfigCache interface signature
internal/execute/tsc/extendedconfigcache.go	Updated to match new ExtendedConfigCache interface signature
internal/project/compilerhost.go	Updated to create ParseCacheKey with hash parameter
internal/project/project.go	Updated Ref call to use NewParseCacheKey with hash
internal/project/snapshot.go	Updated Deref call to use NewParseCacheKey with hash
internal/project/session.go	Updated cache initialization to use new constructors; updated type annotations in cache stats logging
internal/project/refcountcache_test.go	Updated test assertions to reflect new behavior where changed files create new cache entries
internal/project/configfilechanges_test.go	Added new test for doubly-extended config file changes to verify bug fix
internal/fourslash/fourslash.go	Updated ParseCache initialization to use new constructor
internal/ast/ast.go	Added Hash field to SourceFile struct