python / python/cpython

Incorrect SyntaxError attributes when raised by `compile`

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interpreter-core type-bug
Linguagem predominante
Python
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Descrição

Bug report

Bug description:

This is probably a problem with compile, and I will demonstrate it through ast.parse. Consider the following code in a file f.py.

import ast

code = "x y"
ast.parse(code, filename='f.py')

This correctly raises a SyntaxError with lineno = 1 and offset = 3 since the error is at the beginning of y in the code. However, the traceback points into the file f.py itself, instead of the string code. Notice that it points to the third column of the first line of f.py.

  File "f.py", line 1
    import ast
      ^
SyntaxError: invalid syntax

This does not happen for any other string given as filename to ast.parse. In general, the traceback seems to point with the "correct" lineno and offset to the code in the file itself instead of code given to ast.parse. However, the problem is slightly more nuanced. If the offset in the string given to ast.parse is more than the length of the corresponding line in f.py, the offset attribute of the SyntaxError raised is incorrectly set to the length of the corresponding line in f.py plus two. Consider the following code in f.py.

import ast

code = "                                     x y"
ast.parse(code, filename='f.py')

This raises the following exception.

  File "f.py", line 1
    import ast
              ^
IndentationError: unexpected indent

On closer inspection, it turns out that the offset of the exception raised is 12 (note that the length of "import ast" is 10) instead of the correct 37 which is observed when filename is set to anything other than f.py. However, something more interesting happens when the number of lines in the code string is more than the number of lines in the file f.py.

import ast

code = "\n\n\n\nx y"
ast.parse(code, filename='f.py')

The problem goes away!

  File "f.py", line 5
    x y
      ^
SyntaxError: invalid syntax

We even see the correct offset.

CPython versions tested on:

3.11, 3.12, 3.13

Operating systems tested on:

Linux

(Edit) Incorrect text attribute

There is something more going on here. The following issue can be seen in 3.11 and 3.12 but not in 3.13. Consider the following f.py.

import ast

with open('temp.py') as f:
    code = f.read()
ast.parse(code, filename='temp.py')

temp.py is as follows.

"""                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             """; x """                                                                                                                                                         """; foobar

This leads to the following traceback.

  File "temp.py", line 1
    foobar
          ^
SyntaxError: invalid syntax

Besides the fact that the offset is incorrectly set to 8 (instead of 840), the text is incorrectly set to foobar (on 3.13, the entire file contents of temp.py are present in text). This problem goes away if filename is set to anything else. The problem also goes away if the contents of temp.py are shorter!

Guia de contribuição

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Direção de pesquisa

Comece reproduzindo os exemplos usando ast.parse e compile, comparando os atributos de SyntaxError quando filename corresponde ao arquivo-fonte e quando não corresponde. Rastreie como traceback, offset e text são preenchidos para nomes de arquivo correspondentes. O trabalho estará concluído quando lineno, offset, text e traceback descreverem consistentemente a string analisada nos casos demonstrados, com cobertura de regressão para os exemplos.

Escrita pelo modelo de indexação a partir do texto da issue.

Avaliação

Stack de tecnologia
python
Domínio
compilers
Tipo de issue
Bug
Dificuldade
4/5
Tempo estimado
3-5 dias
Status de atividade
Estagnada
Clareza
Razoavelmente clara
Facilidade para iniciantes
38/100

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