How do you know what to cleanup when you have no idea which APIs might throw, what stack frames might have been skipped when they do throw, and what state was left broken by yeeting a stack-unwinding exception up your call stack?
You can only assume that the methods you have called have left their own work in a consistent state despite having thrown an exception. If they haven't, then they themselves have bugs and the appropriate cleanup code needs to be added there. Or, if it's a third party library, you should file a bug report or pull request with their maintainers.
You don't try to clean up other people's work for them. That would just cause confusion and result in messy, tightly coupled code that is hard to understand and reason about.
var myFile = File.Open(filename);
try {
while ((var s = file.ReadLine()) != null) {
var entity = ProcessLine(s);
// do whatever you need to do to entity
}
}
finally {
myFile.Dispose();
}
using (var myFile = File.Open(filename)) {
while ((var s = file.ReadLine()) != null) {
ProcessLine(s);
// do whatever you need to do to entity
}
}It's certainly far, far better than having to add exactly the same check after every method call. Which is only what you need to do if you're working in a situation where exceptions are not an option.
As a bonus, you can’t accidentally fail to catch an exception, and you can model much more complex error handling than just ”catch and raise.”
For example, it’s trivial to implement error recovery, where you implicitly collect all errors that occurred and then can report them once at the end.