bpo-39999: Improve compatibility of the ast module. #19056
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* Re-add removed classes Suite, Param, AugLoad and AugStore. * Add docstrings for dummy classes. * Add docstrings for attribute aliases. * Set __module__ to "ast" instead of "_ast".
Lib/ast.py
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| class Suite(mod): | ||
| """Unused AST node class.""" | ||
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| class AugLoad(expr_context): | ||
| """Unused AST node class.""" | ||
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| class AugStore(expr_context): | ||
| """Unused AST node class.""" | ||
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| class Param(expr_context): | ||
| """Unused AST node class""" |
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Should we deprecate this as well?
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I used word "deprecated" if it was used in past Python releases and the user code can use them for compatibility. I used word "unused" if it was not used in Python (at least in Python 3) and there is no reason to use it in the user code.
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But aren't them will be removed in time or stay them forever? If they will, wouldn't it be good to start doing warnings?
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It would be better to start emitting warnings when the user code can just drop these classes. Currently Param is needed for 2.7, and some projects still support it.
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Currently Param is needed for 2.7, and some projects still support it.
Oh, that makes sense.
pablogsal
changed the title
Lib/ast.py
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| Constant.n = property(_getter, _setter) | ||
| Constant.s = property(_getter, _setter) | ||
| Constant.n = property(_getter, _setter, doc='Deprecated. Use value instead.') | ||
| Constant.s = property(_getter, _setter, doc='Deprecated. Use value instead.') |
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Would it be possible to emit a DeprecationWarning when it's used?
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Yes, it is possible. But it would be better to start emitting warnings when the user code no longer need to use the deprecated feature. I.e. when the support of Python 3.7 be dropped in most projects which use AST.
| @@ -564,22 +568,40 @@ def __new__(cls, *args, **kwargs): | |||
| type(...): 'Ellipsis', | |||
| } | |||
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| class Index(AST): | |||
| class slice(AST): | |||
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@serhiy-storchaka what do you think about implementing custom instance and subclass checks for slice? slice is a sum type, so there should be checks like this issubclass(thing, ast.slice) or isinstance(thing, ast.slice)
something like this should work
def __subclasscheck__(self, subclass):
if issubclass(subclass, Slice):
return True
else:
return super().__subclasscheck__(subclass)
def __instancecheck__(self, instance):
if isinstance(instance, Slice):
return True
else:
return super().__instancecheck__(instance)There was a problem hiding this comment.
Before the simplification, it was part of slice kind. Now it is an expression by it is own but if we want to increase compatibility, wouldn't it better to it behave like a subclass of ast.slice?
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I do not think it would be useful because Index() can return arbitrary node type and it is impossible to distinguish ExtSlice from Tuple.
* Re-add removed classes Suite, slice, Param, AugLoad and AugStore. * Add docstrings for dummy classes. * Add docstrings for attribute aliases. * Set __module__ to "ast" instead of "_ast".
__module__to "ast" instead of "_ast".https://bugs.python.org/issue39999