I am not convincing this is the right solution. This will hide the real error and as the traceback is missing will make it very difficult to find out what the problem is. The real solution is probably to filter the candidates in the traceback module before submitting it to the _generate_suggestions function.

@ambv @iritkatriel what do you think?

I agree with @pablogsal.

Either filter in traceback, or error out in runpy when the globals dict is weird.

Thank you both for the review, sorry for taking so long to address it.

Either filter in traceback, or error out in runpy when the globals dict is weird.

runpy is just an easy path to a NameError with a user provided globals, but it also works with e.g.:

>>> g = {0:1, "p": 1}
>>> exec(compile("pa", 'g', "exec"), g)
[...]
NameError: name 'pa' is not defined
During handling of the above exception, another exception occurred:
[...]
TypeError: all elements in 'candidates' must be strings
[And the REPL exits]

So, the current situation in trackeback._compute_suggestion_error() is:

• ImportError: if the module has a non-string in its __dict__, no suggestion is offered and no error happens.
• AttributeError: object returns a non-string in its __dir__ (or has one in __dict__), no suggestion is offered and no error happens.
• NameError: if f_locals, f_globals or f_builtins has a non-string key, an error is raised that exits the new REPL.

I suggest we just guard against an exception in the NameError case and offer no suggestions (by returning None). An alternative that gets the same result is to return None if a check like any(not isinstance(x, str) for x in candidates) succeeds.

Or we can filter non-strings from the candidates in the NameError case, which would provide suggestions while avoiding the error. If this is preferred, I suggest to also filter non-strings in the ImportError and AttributeError cases, for the same effect.

@devdanzin If you just want to fix the crash, this one-liner does the job:

diff --git a/Lib/traceback.py b/Lib/traceback.py
index 647c23ed782..cd5e2a88f07 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -1527,6 +1527,7 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
             + list(frame.f_globals)
             + list(frame.f_builtins)
         )
+        d = [name for name in d if isinstance(name, str)]
 
         # Check first if we are in a method and the instance
         # has the wrong name as attribute

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Gentle ping @iritkatriel @pablogsal . Should we go with guarding against the exception and not offering suggestions on NameError case? What's your preference?

Non-string keys are legal in dicts. Hints are an excellent by optional (and CPython-specific, I presume) enhancement. The hinters should just ignore, by filtering out, non-string keys and give a hint if possible. There is no reason to not give hint. Hinters are not linters.