Improve exception message in ast.literal_eval #77069

Activity

1. Rosuav commented on Feb 20, 2018

   

   Rosuav

   on Feb 20, 2018

   ContributorAuthor

   More actions

   When a non-literal is given to literal_eval, attempt to be more
   helpful with the message, rather than calling it 'malformed'.
2. Rosuav

   added

   3.8 (EOL)end of lifeend of life

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Feb 20, 2018
3. serhiy-storchaka commented on Feb 20, 2018

   

   serhiy-storchaka

   on Feb 20, 2018

   Member

   More actions

   I afraid this makes an error message more confusing and misleading.

   >>> ast.literal_eval('~2')
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/serhiy/py/cpython/Lib/ast.py", line 93, in literal_eval
       return _convert(node_or_string)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 92, in _convert
       return _convert_signed_num(node)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 65, in _convert_signed_num
       return _convert_num(node)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 56, in _convert_num
       raise ValueError('%s not allowed in literal' % type(node).__name__)
   ValueError: UnaryOp not allowed in literal

   This is not true since + and - are allowed:

   >>> ast.literal_eval('-2')
   -2
   
   >>> ast.literal_eval('2+3')
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/serhiy/py/cpython/Lib/ast.py", line 93, in literal_eval
       return _convert(node_or_string)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 92, in _convert
       return _convert_signed_num(node)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 65, in _convert_signed_num
       return _convert_num(node)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 56, in _convert_num
       raise ValueError('%s not allowed in literal' % type(node).__name__)
   ValueError: BinOp not allowed in literal

   But:

   >>> ast.literal_eval('2+3j')
   (2+3j)
   
   >>> ast.literal_eval('"a"+"b"')
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/serhiy/py/cpython/Lib/ast.py", line 93, in literal_eval
       return _convert(node_or_string)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 85, in _convert
       left = _convert_signed_num(node.left)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 65, in _convert_signed_num
       return _convert_num(node)
     File "/home/serhiy/py/cpython/Lib/ast.py", line 56, in _convert_num
       raise ValueError('%s not allowed in literal' % type(node).__name__)
   ValueError: Str not allowed in literal

   But Str is allowed:

   >>> ast.literal_eval('"ab"')
   'ab'
4. Rosuav commented on Feb 20, 2018

   

   Rosuav

   on Feb 20, 2018

   ContributorAuthor

   More actions

   Hmm, I think I see what I broke there. It was part of the merge conflict resolution - I moved the check into the function, which is actually incorrect. It wasn't misleading like that in the original patch. Will fix that.
5. Rosuav commented on Feb 20, 2018

   

   Rosuav

   on Feb 20, 2018

   ContributorAuthor

   More actions

   Actually, it's a bit more complicated than I thought. Current proposed solution: Track the context of each conversion, thus allowing different errors to be distinguished.
6. Rosuav commented on Feb 20, 2018

   

   Rosuav

   on Feb 20, 2018

   ContributorAuthor

   More actions

   (BTW, by "proposed" I mean that the change that I describe is in the PR.)
7. serhiy-storchaka commented on Jul 3, 2018

   

   serhiy-storchaka

   on Jul 3, 2018

   Member

   More actions

   Please wait until bpo-32892 and bpo-32893 be committed or rejected before merging this PR.
8. ezio-melotti

   transferred this issue fromon Apr 10, 2022