`concurrent.interpreters.Interpreter.exec` propagate `SyntaxError`

[muxator]

Bug report

Bug description:

Hi,

I am testing the concurrent.interpreters feature from Python 3.14rc3 (the latest current rc).

The subinterpreter seems to behave in a surprising way when encountering syntax errors. For example, in the following code:

from concurrent import interpreters

interpr = interpreters.create()

def exec_catching_errors(code: str) -> None:
    try:
        interpr.exec(code)
    except interpreters.ExecutionFailed as e:
        print(f"There was an error: {e}")
    print("The function ends")


exec_catching_errors("print(1/0)")
exec_catching_errors("print 1")  # this is the surprising line

# the whole script dies with an uncaught SyntaxError

• trying to execute print(1/0) causes an interpreters.ExecutionFailed that correctly wraps a ZeroDivisionError.
• trying to execute print 1 causes a bare SyntaxError, whereas I would have expected a subclass of interpreters.InterpreterError wrapping the SyntaxError.

Is this intended behaviour, a bug, or something that simply needs to be better documented?

Thanks

CPython versions tested on:

3.14

Operating systems tested on:

Linux

[serhiy-storchaka]

I think this is expected behavior. If you call interpr.exec() with wrong number or type of arguments, you will get TypeError. Compilation occurs in the current interpreter, only the code itself is executed in the different interpreter.

cc @ericsnowcurrently

[ericsnowcurrently]

@serhiy-storchaka is correct. Execution failed means what it says, that executing the code failed Failures when compiling or serializing or otherwise not actually running the code will raise normally.

That said, it would probably be worth making sure the docs are clear about this.