Error Reporting

This is a guide for rascal developers on how to report errors to the user.

There are only 2 kinds of errors:

1. errors the user should see
2. errors only a rascal developer should see

Error reporting to a user

Always write to the evaluator.getStdErr() stream. Getting the reference to the evaluator is often just a . away.

What will happen with the error?

• Function called from console: the error will print in the console
• Function called as a callback (vis-framework, ide-contributions): the error will always print in the output window

Error reporting to the developer

Always send the exception to Activator.log(msg, exception), (no need for the .getInstance() call). Or if you are just debugging, send it to System.err.

What will happen with the error?

It will be reported to the errors view, which is not part of the default rascal perspective. So never report an error to this if the user might be interested in the fact that the code failed.