spec_transaction_with_transaction

## Value

dbWithTransaction() returns the value of the executed code. Failure to initiate the transaction (e.g., if the connection is closed or invalid of if dbBegin() has been called already) gives an error.

## Specification

dbWithTransaction() initiates a transaction with dbBegin(), executes the code given in the code argument, and commits the transaction with dbCommit(). If the code raises an error, the transaction is instead aborted with dbRollback(), and the error is propagated. If the code calls dbBreak(), execution of the code stops and the transaction is silently aborted. All side effects caused by the code (such as the creation of new variables) propagate to the calling environment.