getCompletionsAtPosition in API deadlocks when used with includeSymbol: true #64166

🔎 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:

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

The same goroutine first acquires the checker here

Then it tries to acquire the same checker again here

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