Fix API server panic when opening a JS file that a tsconfig does not include - #65436

Opening a .js/.mjs file through the API panics with a nil dereference in acquireConfigForFile → SyncMapEntry.ChangeIf when the nearest tsconfig includes no files. With the fix, the file opens in the inferred project, as it did in 7.0.2.

// tsconfig.json: {}   w.mjs: export const a = 1
api.createSnapshot({ openFiles: [cwd + "/w.mjs"] }); // panicked

Root cause

HandleAPIRequest looks up the config for each opened file twice in the same builder, with a cleanup in between:

1. OpenFiles pass: acquires the tsconfig. There are no root files, so no project retains it, and API-opened files don't retain it either.
2. cleanupConfiguredProjects: deletes the unretained entry from the builder's dirty.SyncMap.
3. EnsureFiles pass: acquires the same tsconfig again. LoadOrStore returns (nil, false) for a key deleted earlier in the builder, and the caller dereferences nil.

A later updateSnapshot that opens another stray JS file hits the same path through LoadOrStore's base-map branch.

Changes

• dirty.SyncMap.LoadOrStoreReplacingDeleted (new): like LoadOrStore, but if the key was deleted earlier in the builder, it stores the new value in that entry and returns it instead of nil.
  • LoadOrStore is unchanged: snapshotfs relies on its nil return to keep files deleted in a snapshot from being re-cached.
• configFileRegistryBuilder: acquireConfigForFile, acquireConfigForProject and updateExtendingConfigs use the new method. A config that Cleanup removed earlier in the same snapshot is recreated and parsed again.

Tests

• TestOpenFileNotIncludedByConfigOpensInInferredProject (internal/api):
  • covers w.mjs next to the tsconfig and src/nested/w.js two levels below it;
  • then calls updateSnapshot to open a second stray .cjs;
  • asserts every opened file lands in the inferred project.
• TestSyncMapLoadOrStoreDeletedKey (internal/project/dirty): checks both lookup methods on deleted base keys and deleted added keys, and checks the finalized result.

Not addressed

findOrCreateProject → configuredProjects.LoadOrStore has the same "deleted earlier in this builder returns nil" behavior. Its callers treat nil as "not found", and this issue's steps don't reach it.

• Fixes API server panics in acquireConfigForFile when opening a JS file a tsconfig does not include #65054