lib2to3 does not accept "exec" as name #88425

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1. Mulugruntz commented on May 28, 2021

   

   Mulugruntzmannequin

   on May 28, 2021

   MannequinAuthor

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   I was trying to use https://github.com/NiklasRosenstein/pydoc-markdown to generate some doc for https://github.com/Mulugruntz/aiosubprocess

   It was failing and for a while I thought I was doing something wrong. But when I did dig deeper, I realized that it was failing because I has a method named "exec".

   The reason why I want to use "exec" is to make it obvious whether I'm executing the subprocess in shell mode or not (there's also a "shell" method).

   As we can see here https://docs.python.org/3.9/reference/lexical_analysis.html#keywords

   "exec" is not reserved.

   Moreover, it's pretty counterintuitive that the code parses and runs correctly (cpython 3.9.5) but the lib2to3 parser crashes.

   See below a working example:

   from lib2to3 import pygram, pytree
   from lib2to3.pgen2 import driver
   from lib2to3.pgen2.parse import ParseError
   
   grammar = pygram.python_grammar.copy()
   driver = driver.Driver(grammar, convert=pytree.convert)
   
   strings = [
       "def fname(): pass",
       "def exec(): pass",
       """
   class C:
       def exec(self): pass""",
   ]
   
   for s in strings:
       try:
           driver.parse_string(s + '\n')
       except ParseError as pe:
           print("It fails:", s)
       else:
           print("It works:", s)

   It works: def fname(): pass
   It fails: def exec(): pass
   It fails: 
   class C:
       def exec(self): pass
2. Mulugruntz

   added

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   3.9 (EOL)end of lifeend of life

   topic-2to3

   on May 28, 2021
3. terryjreedy commented on May 28, 2021

   

   terryjreedy

   on May 28, 2021

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   'exec' was a keyword in 2.x, but that should not matter in 3.9. What OS? Did you get an actual crash (core dump on *nix), or a python exception and traceback (not a crash)? If the latter, copy and paste it.
4. Mulugruntz commented on May 29, 2021

   

   Mulugruntzmannequin

   on May 29, 2021

   MannequinAuthor

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   Traceback (most recent call last):
     File "/Users/sgiffard/Library/Application Support/JetBrains/PyCharm2020.3/scratches/scratch_24.py", line 9, in <module>
       driver.parse_string("""class C:\n    def exec(self): pass\n""")
     File "/usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib2to3/pgen2/driver.py", line 103, in parse_string
       return self.parse_tokens(tokens, debug)
     File "/usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib2to3/pgen2/driver.py", line 71, in parse_tokens
       if p.addtoken(type, value, (prefix, start)):
     File "/usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib2to3/pgen2/parse.py", line 162, in addtoken
       raise ParseError("bad input", type, value, context)
   lib2to3.pgen2.parse.ParseError: bad input: type=1, value='exec', context=(' ', (2, 8))
5. Mulugruntz commented on May 29, 2021

   

   Mulugruntzmannequin

   on May 29, 2021

   MannequinAuthor

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   Sorry, I forgot to mention:
   macOS Mojave 10.14.5 (18F132)
6. iritkatriel commented on Sep 7, 2021

   

   iritkatriel

   on Sep 7, 2021

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   Changing type as crash typically refers to segfault and not an exception.
7. iritkatriel

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   and removed

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   on Sep 7, 2021
8. iritkatriel

   closed this as completedon Oct 20, 2021
9. iritkatriel

   closed this as completedon Oct 20, 2021
10. ezio-melotti

    transferred this issue fromon Apr 10, 2022
11. Mulugruntz commented on Apr 15, 2022

    

    Mulugruntz

    on Apr 15, 2022

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    Hi @iritkatriel , do we know the readon why it was closed?
12. iritkatriel commented on Apr 15, 2022

    

    iritkatriel

    on Apr 15, 2022

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    lib2to3 is deprecated, core devs will not be working on it anymore.