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compile(optimize=2) doesn't del docstrings/asserts, ignores -OO & PYTHONOPTIMIZE=2 #112909

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dreamflow opened this issue Dec 9, 2023 · 3 comments
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compile(optimize=2) doesn't del docstrings/asserts, ignores -OO & PYTHONOPTIMIZE=2 #112909

dreamflow opened this issue Dec 9, 2023 · 3 comments
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@dreamflow
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dreamflow commented Dec 9, 2023 •
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Bug report

Bug description:

import ast
py_test_source = '''
def test() :
    """docstring"""
    assert True
    ...
'''
ast_obj = compile( # https://docs.python.org/library/functions.html#compile
    source = py_test_source ,
    filename = "" ,
    mode = "exec" ,
    flags = ast.PyCF_ONLY_AST ,
    dont_inherit = 1 ,
    optimize = 2 ,
) 
print( ast.unparse( ast_obj ) )

as i understand the compile() documentation ,
the above example should remove the docstring ,
and the assert line , but it doesn't .

setting the env var PYTHONOPTIMIZE=2 and then
running python with the cmdLine option -OO
this time with
a) compile( ... , dont_inherit=False , ... ) without optimize
b) compile( ... , dont_inherit=0 , ... ) without optimize
c) compile( ... ) without : dont_inherit , optimize
didn't chage the outcome :
compile() never removes docstrings/asserts .

looks like compile() ignores its arg optimize=2
and -OO and PYTHONOPTIMIZE=2 .

CPython versions tested on:

3.11.5

Operating systems tested on:

Windows 10 (22H2) 64bit
@dreamflow dreamflow added the type-bug An unexpected behavior, bug, or error label Dec 9, 2023
@dreamflow dreamflow changed the title compile( optimize=2 ) doesn't del docstrings , ignores -OO & PYTHONOPTIMIZE=2 compile( optimize=2 ) doesn't del asserts/docstrings , ignores -OO & PYTHONOPTIMIZE=2 Dec 9, 2023
@dreamflow dreamflow changed the title compile( optimize=2 ) doesn't del asserts/docstrings , ignores -OO & PYTHONOPTIMIZE=2 compile( optimize=2 ) doesn't del docstrings/asserts , ignores -OO & PYTHONOPTIMIZE=2 Dec 9, 2023
@terryjreedy terryjreedy added pending The issue will be closed if no feedback is provided and removed type-bug An unexpected behavior, bug, or error labels Dec 10, 2023
@terryjreedy
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The doc says "The argument optimize specifies the optimization level of the compiler;". With the PyCF_ONLY_AST, you are only running the parser, not the compiler itself. If the parser stripped docstrings and assert statements, then unparse would not work right. Also, def f(): "docstring"` would not compile as the docstring is, here, the required non-empty suite.

If you compile to a code object and exec the code object, the resulting test function object will not have a docstring or assert.

test = '''\
def test() :
    """docstring"""
    assert False
'''

exec(compile( 
    source = test,
    filename = "" ,
    mode = "exec" ,
#    flags = ast.PyCF_ONLY_AST ,
    dont_inherit = 1 ,
    optimize = 2 ,
))

print(test.__doc__, test())  # prints `None None`

Perhaps the doc could be clearer to Python learners, but I am not sure how.

@dreamflow
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dreamflow commented Dec 10, 2023 •
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thank you terryjreedy for the detailed explanation 🙂

@hugovk hugovk changed the title compile( optimize=2 ) doesn't del docstrings/asserts , ignores -OO & PYTHONOPTIMIZE=2 compile(optimize=2 ) doesn't del docstrings/asserts , ignores -OO & PYTHONOPTIMIZE=2 Dec 10, 2023
@hugovk hugovk changed the title compile(optimize=2 ) doesn't del docstrings/asserts , ignores -OO & PYTHONOPTIMIZE=2 compile(optimize=2) doesn't del docstrings/asserts, ignores -OO & PYTHONOPTIMIZE=2 Dec 10, 2023
@carljm
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carljm commented Dec 17, 2023

This is a duplicate of #108113. In #108154 @iritkatriel added PyCF_OPTIMIZED_AST to solve this (but for Python 3.13+ only.)

@carljm carljm closed this as completed Dec 17, 2023
@carljm carljm closed this as not planned Won't fix, can't repro, duplicate, stale Dec 17, 2023
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