Make List[Node] covariants #6
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cocoatomo
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Nov 27, 2018
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docutils-stubs/nodes.pyi
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| @@ -11,6 +11,7 @@ from typing import Any, Callable, Dict, Iterable, Iterator, List, Optional, over | |||
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| __docformat__: str | |||
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| T_co = TypeVar('T', bound=nodes.Node, covariant=True) | |||
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- By convention, the name of the first argument of TypeVar should be a name of variable on the left-hand side.
- TypeVar with name
T_colooks like covariant type variable having upper boundobject. A name indicating that its upper bound isnodes.Nodeis more preferable.
Examples can be taken from the implementation of typing module::
CT_co = TypeVar('CT_co', covariant=True, bound=type)
https://github.com/python/cpython/blob/f2a9d5c8378cd7eca90b3b197e2cc0989da55014/Lib/typing.py#L1181
docutils-stubs/nodes.pyi
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| @@ -38,7 +39,7 @@ def ensure_str(s: str) -> str: ... | |||
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| class Text(Node, str): | |||
| tagname: str = ... | |||
| children: Tuple[nodes.Node, ...] = ... | |||
| children: Tuple[T_co, ...] = ... | |||
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By default, Tuple is covariant because it is immutable, while List is mutable.
So, this change is not necessary.
For more detail, refer following comment and PEP,
- Covariance or contravariance python/typing#2 (comment)
- https://www.python.org/dev/peps/pep-0484/#covariance-and-contravariance
"The read-only collection classes in typing are all declared covariant in their type variable (e.g. Mapping and Sequence)."
docutils-stubs/nodes.pyi
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| @@ -93,7 +94,7 @@ class Element(Node): | |||
| def __contains__(self, attr: str) -> bool: ... | |||
| def get_language_code(self, fallback: str = ...) -> str: ... | |||
| def append(self, item: nodes.Node) -> None: ... | |||
| def extend(self, item: Iterable[nodes.Node]) -> None: ... | |||
| def extend(self, item: Iterable[T_co]) -> None: ... | |||
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This change is not necessary for the same reason as Tuple.
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Minimum examples are following, from typing import *
bool_tuple: Tuple[bool, bool, bool] = (True, False, True)
int_tuple: Tuple[int, int, int] = bool_tuple # OK
bool_iterable: Iterable[bool] = (b for b in [True, False, True])
int_iterable: Iterable[int] = bool_iterable # OK
bool_list: List[bool] = [True, False, True]
int_list: List[int] = bool_list # type error |
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Updated! |
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cocoatomo
requested changes
Nov 28, 2018
docutils-stubs/writers/manpage.pyi
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| from typing import Any, Callable, Dict, List, Optional, Pattern, Tuple, Type | ||
| from typing import Any, Callable, Dict, List, Optional, Pattern, Tuple, Type, TypeVar | ||
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| N_co = TypeVar('N_co', bound=nodes.Node, covariant=True) |
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TypeVar N_co is not used in manpage.pyi file.
Would you aim at using this TypeVar in order to fix the type of Translator.colspec?
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oh, sorry. It was mistake. removed.
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cocoatomo
reviewed
Nov 28, 2018
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I'll ship this after merging this. But it should be separated this PR itself. |
cocoatomo
approved these changes
Nov 28, 2018
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