Uninformative syntax errors from codeop._maybe_compile (IDLE Shell)

[Mehdical-Man]

>>> def function(duplicate, duplicate):
...     pass
# Expected error message:
SyntaxError: duplicate argument 'duplicate' in function definition
# Actual error message:
SyntaxError: incomplete input

>>> def global_and_parameter(argument, /):
...    global argument # It may not be clear for less experienced coders
                       # that a name cannot be global and parameter
SyntaxError: incomplete input
# However when executed with exec():
SyntaxError: name 'argument' is parameter and global

Linked PRs

• gh-111366: Correctly show custom syntax error messages in the codeop module functions #111384
• [3.11] gh-111366: Correctly show custom syntax error messages in the codeop module functions (GH-111384). #111516
• [3.12] gh-111366: Correctly show custom syntax error messages in the codeop module functions (GH-111384). #111517

[hugovk]

cc @pablogsal

[hugovk]

Closing as the PRs have been merged. Thanks for the report!

[terryjreedy]

Either codeop is not fixed for errors on line 1 or code is using codeop wrong. Fresh compile after update:

f:\dev\3x>python
# REPL splash lines
>>> def f(x,x): pass
...
SyntaxError: duplicate argument 'x' in function definition

# Switch  to simulated REPL, also used by IDLE, with same result.
>>> import code
>>> code.interact()
(InteractiveConsole)
>>> def f(x,x): pass
  File "<console>", line 1
    def f(x,x): pass
SyntaxError: invalid syntax
# Improvement over "incomplete input" in released versions (at least in IDLE), but not best.
>>> def f(x,x):
...   pass
  File "<console>", line 1
SyntaxError: duplicate argument 'x' in function definition

[terryjreedy]

I still think that the fix for ._maybe_compile is to expose the REPL logic disintangled from terminal interaction, much as Python tokening code in tokenize was replaced by access to the real tokener. I have the impression that Pablo has taken steps toward the needed separation.

[hugovk]

(Feel free to reopen this issue if needed)