fix: clear error when sql_variant used in TVP columns

[dhensby]

Summary

Fixes #1796.

When a TVP contains sql_variant columns, the tedious driver throws an unhelpful uncaught exception because its sql_variant type has all serialization methods (generateTypeInfo, validate, generateParameterLength, generateParameterData) stubbed with throw new Error('not implemented').

This PR:

1. Detects sql_variant columns early in parameterCorrection() and throws a clear RequestError explaining the limitation and suggesting a more specific data type.

2. Wraps parameter serialization in try/catch in both _query() and _execute() paths so that errors from parameterCorrection() (and any other parameter processing errors) are properly routed to the callback instead of thrown as uncaught exceptions.

3. Adds a unit test verifying the error message.

Root cause

This is ultimately a limitation in the tedious driver — sql_variant is not implemented for parameter serialization. A full fix would require implementing sql_variant support in tedious itself, which is non-trivial as it is a container type that can hold many different SQL Server types. This PR provides a clear error message in the meantime.

Error message

Before:

RequestError: Input parameter 'Filters' could not be validated

After:

RequestError: Column 'Value1' in TVP 'dbo.GridFilter' uses sql_variant which is not supported by the tedious driver for TVP column types. Consider using a more specific data type.

[dhensby]

@Avi-E-Koenig - how does this look to you?

[Avi-E-Koenig]

@Avi-E-Koenig - how does this look to you?

hi @dhensby this could definitley clear confusion in this use case

[Copilot]

Pull request overview

Improves developer-facing error handling for Table-Valued Parameters (TVPs) containing sql_variant columns when using the tedious driver, preventing unhelpful uncaught exceptions and providing a clearer limitation message.

Changes:

• Detects sql_variant TVP columns during parameter correction and throws a clearer RequestError.
• Wraps parameter addition/serialization with try/catch in _query() and _execute() to route parameter-processing failures to the callback.
• Adds a unit test to assert that the error message mentions sql_variant and the problematic column name.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/tedious/request.js	Adds early sql_variant TVP detection and wraps parameter setup in try/catch for query/execute paths.
test/common/unit.js	Adds a unit test validating the improved error message for sql_variant TVP columns.

Comments suppressed due to low confidence (1)

lib/tedious/request.js:730

• The catch here calls handleError(true, connection, error), but handleError does not delete this._cancel and (when this.stream === true) it will emit error without removing listeners / releasing the borrowed connection / invoking the callback. For errors thrown before execSql/execSqlBatch is called (e.g., from parameterCorrection()), this can leak the connection and leave a stale _cancel function pointing at a released connection. Consider handling this catch as a fatal pre-exec failure: remove the event listeners, delete this._cancel, release the connection, mark hasReturned, and surface the original error (without re-wrapping if it’s already a RequestError).

        try {
          if (!this._isBatch) {
            for (const name in this.parameters) {
              if (!objectHasProperty(this.parameters, name)) {
                continue
              }
              const param = this.parameters[name]
              if (param.io === 1) {
                req.addParameter(param.name, getTediousType(param.type), parameterCorrection(param.value), { length: param.length, scale: param.scale, precision: param.precision })
              } else {
                req.addOutputParameter(param.name, getTediousType(param.type), parameterCorrection(param.value), { length: param.length, scale: param.scale, precision: param.precision })
              }
            }
          }

          connection[this._isBatch ? 'execSqlBatch' : 'execSql'](req)
        } catch (error) {
          handleError(true, connection, error)
        }

[github-actions]

🎉 This PR is included in version 12.3.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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