useKernel = true, can not get real error

[anson-ng-appier]

hi owner
we found

  const connectOptions: DatabricksConnectOptions = {
    authType: 'databricks-oauth',
    host: dbConfig.host,
    path: dbConfig.httpPath,
    oauthClientId: dbConfig.clientId,
    oauthClientSecret: dbConfig.clientSecret,
    useKernel: true
  }
  const _client = new DBSQLClient()
  await _client.connect(connectOptions)
  const session = await _client.openSession()
  const sql = `SELECT try_cast('' as ARRAY<STRING>)`
  const op = await session.executeStatement(sql)
  await op.finished()


will throw 
DriverError: kernel backend: unknown error
    at decodeNapiKernelError (...) {stack: 'Error: kernel backend: unknown error
    )', message: 'kernel backend: unknown error'}

if useKernel: false , will get real error

    [DATATYPE_MISMATCH.CAST_WITHOUT_SUGGESTION] Cannot resolve "" due to data type mismatch: cannot cast "STRING" to "ARRAY<STRING>". SQLSTATE: 42K09; line 1 pos 7

[msrathore-db]

Hi @anson-ng-appier - thanks for the report.

We tried hard to reproduce this and could not on the released builds. Running your exact query SELECT try_cast('' as ARRAY) with useKernel: true against a live warehouse, on @databricks/sql@1.16.0 (ships kernel binary 0.2.0), the real error comes through correctly:

OperationStateError: [DATATYPE_MISMATCH.CAST_WITHOUT_SUGGESTION] Cannot resolve "" due to data type mismatch:
cannot cast "STRING" to "ARRAY". SQLSTATE: 42K09

(verified with both PAT and databricks-oauth M2M, sync and async, on linux-x64).

The kernel backend: unknown error message you saw is a fallback the driver only emits when the rejected value fails an err instanceof Error check. That almost always means the real error object exists but is being checked against a different JavaScript realm's Error - which happens when there are multiple/bundled copies of the package, or the driver runs across a worker_threads / vm boundary. To pin it down, could you share:

1. Exact versions - output of:
   npm ls @databricks/sql
   npm ls | grep databricks-sql-kernel
   node -v
2. and your OS + arch (Windows/macOS/Linux, x64/arm64).
3. How the app runs the driver - is it bundled (webpack / esbuild / Next.js / Electron / pkg / ts-node), run inside worker_threads, or is there more than one copy of @databricks/sql in your dependency tree?
4. The raw error, by logging these fields in your catch:
   } catch (e) {
   console.log({
   instanceofError: e instanceof Error,
   brand: Object.prototype.toString.call(e),
   ctor: e?.constructor?.name,
   message: e?.message,
   stack: e?.stack,
   });
   }
5. Does a plain standalone script (node repro.js, no bundler/worker) reproduce it, or only inside your app?

If you're on a pre-1.16.0 preview/build, upgrading to @databricks/sql@1.16.0 should also resolve it. Thanks!

[msrathore-db]

@anson-ng-appier Just checking again if you're facing that issue still and can provide the relevant information