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symtable.Symbol.is_local() can be True for global symbols #84377

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coproc mannequin opened this issue Apr 5, 2020 · 8 comments
Closed

symtable.Symbol.is_local() can be True for global symbols #84377

coproc mannequin opened this issue Apr 5, 2020 · 8 comments
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@pablogsal
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3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@coproc
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Mannequin

coproc mannequin commented Apr 5, 2020

BPO 40196
Nosy @pablogsal, @miss-islington
PRs
  • bpo-40196: Fix a bug in the symtable when reporting inspecting global variables #19391
  • [3.8] bpo-40196: Fix a bug in the symtable when reporting inspecting global variables (GH-19391) #19394
  • [3.7] bpo-40196: Fix a bug in the symtable when reporting inspecting global variables (GH-19391) #19395
    		•
    Files
  • global_and_local.py: console output (as in comment) shows that for global symbol 'e' also is_local() returns True
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/pablogsal'
closed_at = <Date 2020-04-06.16:42:07.698>
created_at = <Date 2020-04-05.13:30:26.178>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'symtable.Symbol.is_local() can be True for global symbols'
updated_at = <Date 2020-04-06.16:42:07.698>
user = 'https://bugs.python.org/coproc'

    bugs.python.org fields:

    activity = <Date 2020-04-06.16:42:07.698>
actor = 'pablogsal'
assignee = 'pablogsal'
closed = True
closed_date = <Date 2020-04-06.16:42:07.698>
closer = 'pablogsal'
components = ['Library (Lib)']
creation = <Date 2020-04-05.13:30:26.178>
creator = 'coproc'
dependencies = []
files = ['49037']
hgrepos = []
issue_num = 40196
keywords = ['patch']
message_count = 8.0
messages = ['365820', '365821', '365845', '365853', '365855', '365868', '365870', '365871']
nosy_count = 3.0
nosy_names = ['pablogsal', 'miss-islington', 'coproc']
pr_nums = ['19391', '19394', '19395']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40196'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9']
    @coproc
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    Mannequin Author

    coproc mannequin commented Apr 5, 2020

    Consider this function:

    def f():
	global e
	e = 1

    When inspecting symbols with symtable, symbol 'e' will be global and local, whereas is_local() should return False. See the attached file for reproducing. It will output to stdout:

    symbol 'e' in function scope: is_global() = True, is_local() = True
    global scope: e = 1

    @coproc coproc mannequin added 3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir labels Apr 5, 2020
    @coproc
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    coproc mannequin commented Apr 5, 2020

    see https://stackoverflow.com/a/61040435/1725562 for a proposed fix

    @coproc coproc mannequin added type-bug An unexpected behavior, bug, or error labels Apr 5, 2020
    @pablogsal
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    That fix is not correct. For instance consider:

    >>> code2 = """\
... def foo():
...    x = 42
...    def bar():
...       return -1
... """
>>> top.get_children()[0]
<Function SymbolTable for foo in ?>
>>> top = symtable.symtable(code2, "?", "exec")
>>> top.get_children()[0].lookup('x')._Symbol__scope == symtable.LOCAL
True

    but if we return x from bar:

    >>> code = """\
... def foo():
...    x = 42
...    def bar():
...       return x
... """
>>> import symtable
>>> top = symtable.symtable(code, "?", "exec")
>>> top.get_children()[0].lookup('x')._Symbol__scope == symtable.LOCAL
False

    @coproc
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    coproc mannequin commented Apr 6, 2020

    In symtable.Function.get_locals() symbols with scopes in (LOCAL, CELL) are selected. Also

    >>> code = """\
... def foo():
...    x = 42
...    def bar():
...       return x
... """
>>> import symtable
>>> top = symtable.symtable(code, "?", "exec")
>>> top.get_children()[0].lookup('x')._Symbol__scope == symtable.CELL
True

    So I guess this would be the correct fix then:

    def is_local(self):
    return self.__scope in (LOCAL, CELL)

    @pablogsal
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    In symtable.Function.get_locals() symbols with scopes in (LOCAL, CELL) are selected.

    Thanks for pointing that out. I will simplify PR 19391.

    @pablogsal
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    New changeset 799d7d6 by Pablo Galindo in branch 'master':
    bpo-40196: Fix a bug in the symtable when reporting inspecting global variables (GH-19391)
    799d7d6

    @miss-islington
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    New changeset 717f166 by Miss Islington (bot) in branch '3.7':
    bpo-40196: Fix a bug in the symtable when reporting inspecting global variables (GH-19391)
    717f166

    @pablogsal
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    New changeset 8bd84e7 by Miss Islington (bot) in branch '3.8':
    bpo-40196: Fix a bug in the symtable when reporting inspecting global variables (GH-19391) (GH-19394)
    8bd84e7

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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