Code Smell 80 - Nested Try/Catch

Exceptions are a great way of separating happy path versus trouble path. But we tend to over-complicate our solutions.

TL;DR: Don't nest Exceptions. Nobody cares of what you do in the inner blocks.

Problems

Readability

Solutions

Refactor

Sample Code

Wrong

try {
    transaction.commit();
} catch (e) {
    logerror(e);
    if (e instanceOf DBError){
      try {
          transaction.rollback();
      } catch (e) {
          doMoreLoggingRollbackFailed(e);
      }
    }
}

//Nested Try catchs
//Exception cases are more important than happy path
//We use exceptions as control flow

Right

try {
    transaction.commit();
} catch (transactionError) {
    this.withTransactionErrorDo(transationError, transaction);
}

//transaction error policy is not defined in this function
//so we don't have repeated code
//code is more readable
//It is up to the transaction and the error to decide what to do

Detection

We can detect this smell using parsing trees.

Conclusion

Don't abuse exceptions, don't create Exception classes no one will ever catch, and don't be prepared for every case (unless you have a good real scenario with a covering test).

Happy path should always be more important than exception cases.