New submission from Kai Xia <xia...@gmail.com>:
I was trying to construct an ast object dynamically and I think I can identify
some potential issue.
With the following snippet:
```
#!/usr/bin/env python3
import ast
import sys
print(sys.version)
good = ast.Assign(
targets=[ast.Name(id="hello", ctx=ast.Store())],
value=ast.Constant(value="world"),
lineno=1
)
print(ast.unparse(good))
bad = ast.Assign(
targets=[ast.Name(id="hello", ctx=ast.Store())],
value=ast.Constant(value="world"),
)
print(ast.unparse(bad))
```
On my box the output looks like:
```
3.9.6 (default, Jun 29 2021, 05:25:02)
[Clang 12.0.5 (clang-1205.0.22.9)]
hello = 'world'
Traceback (most recent call last):
File "/Users/xiaket/py.py", line 19, in <module>
print(ast.unparse(bad))
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 1572, in unparse
return unparser.visit(ast_obj)
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 801, in visit
self.traverse(node)
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 795, in traverse
super().visit(node)
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 407, in visit
return visitor(node)
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 858, in visit_Assign
if type_comment := self.get_type_comment(node):
File
"/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ast.py",
line 786, in get_type_comment
comment = self._type_ignores.get(node.lineno) or node.type_comment
AttributeError: 'Assign' object has no attribute 'lineno'
```
As I can understand, when we need to construct the Assign object, we'll need to
provide two keyword arguments, targets and value. We don't need to provide the
`lineno` as it should be an attribute of the statement node. Also, if we don't
run `unparse` against the object, apparently it works fine.
I think in the `get_type_comment` method, we are making the assumption that the
lineno is set automatically, this is true when we are parsing python source
code as string. But when we are creating the object from scratch, we don't have
that `lineno` attribute and it will fail.
----------
components: Library (Lib)
messages: 399427
nosy: xiaket
priority: normal
severity: normal
status: open
title: Issue with unparse in ast module
type: behavior
versions: Python 3.9
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44896>
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