`getCompletionsAtPosition` in API deadlocks when used with `includeSymbol: true`

[auvred]

🔎 Search Terms

api, getCompletionsAtPosition, includeSymbol, deadlock

🕗 Version & Regression Information

This bug couldn't be reproduced in any published version because it can only be triggered if the error described in #64132 were fixed

⏯ Playground Link

No response

💻 Code

(note: the reproduction must be run on a #64133 branch, or on main after the PR is merged)

1. Create repro dir

   mkdir /tmp/repro
   cd /tmp/repro
   npm init -y
   npm add typescript@7.0.2
   echo '{}' > tsconfig.json

2. Create files

   // export.ts
   export const someValue = 1
   
   // index.ts
   const foo = {
       
   }
   
   // repro.mjs
   import path from 'node:path'
   import { API } from 'typescript/unstable/sync'
   
   const api = new API()
   const root = process.cwd()
   const file = path.join(root, 'index.ts')
   const tsconfigPath = path.join(root, 'tsconfig.json')
   const snapshot = api.updateSnapshot({ openProject: tsconfigPath })
   const project = snapshot.getProject(tsconfigPath)
   
   console.log(project.checker.getCompletionsAtPosition(file, 15, { includeSymbol:true }))

3. Run repro

   node repro.mjs

🙁 Actual behavior

It hangs forever

🙂 Expected behavior

It returns completion items

Additional information about the issue

This happens because getCompletionsAtPosition uses a context with a checker API lifetime:

TypeScript/tsc/internal/api/session.go

Lines 4005 to 4008 in e73c923

	func (s *Session) handleGetCompletionsAtPosition(ctx context.Context, params *GetCompletionsAtPositionParams) (*CompletionInfoResponse, error) {
	if params.IncludeSymbol {
	ctx = core.WithCheckerLifetime(ctx, core.CheckerLifetimeAPI)
	}

Because of this, there is only one persistent checker is the in checkerpool.

The same goroutine first acquires the checker here

TypeScript/tsc/internal/ls/completions.go

Lines 431 to 432 in e73c923

	checker, done := l.GetProgram().GetTypeCheckerForFile(ctx, file)
	defer done()

Then it tries to acquire the same checker again here

TypeScript/tsc/internal/ls/autoimport/fix.go

Lines 853 to 854 in e73c923

	ch, done := v.program.GetTypeChecker(ctx)
	defer done()

As a result, it silently deadlocks and hangs indefinitely. There is no panic because other goroutines are still active.