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bpo-42345: Fix three issues with typing.Literal parameters #23294

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Nov 17, 2020
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10 changes: 10 additions & 0 deletions Lib/test/test_typing.py
Original file line number Diff line number Diff line change
Expand Up @@ -559,6 +559,16 @@ def test_no_multiple_subscripts(self):
with self.assertRaises(TypeError):
Literal[1][1]

def test_equal(self):
self.assertEqual(Literal[1], Literal[1])
self.assertEqual(Literal[1, 2], Literal[2, 1])
self.assertEqual(Literal[1, 2, 3], Literal[1, 2, 3, 3])

def test_flatten(self):
self.assertEqual(Literal[Literal[1], Literal[2], Literal[3]], Literal[1, 2, 3])
self.assertEqual(Literal[Literal[1, 2], 3], Literal[1, 2, 3])
self.assertEqual(Literal[Literal[1, 2, 3]], Literal[1, 2, 3])
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XK = TypeVar('XK', str, bytes)
XV = TypeVar('XV')
Expand Down
32 changes: 31 additions & 1 deletion Lib/typing.py
Original file line number Diff line number Diff line change
Expand Up @@ -228,6 +228,17 @@ def _remove_dups_flatten(parameters):
return tuple(params)


def _flatten_literal_params(parameters):
"""An internal helper for Literal creation: flatten Literals among parameters"""
params = []
for p in parameters:
if isinstance(p, _LiteralGenericAlias):
params.extend(p.__args__)
else:
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params.append(p)
return tuple(params)


_cleanups = []


Expand Down Expand Up @@ -460,7 +471,11 @@ def open_helper(file: str, mode: MODE) -> str:
"""
# There is no '_type_check' call because arguments to Literal[...] are
# values, not types.
return _GenericAlias(self, parameters)
if not isinstance(parameters, tuple):
parameters = (parameters,)

parameters = _flatten_literal_params(parameters)
return _LiteralGenericAlias(self, parameters)


@_SpecialForm
Expand Down Expand Up @@ -930,6 +945,21 @@ def __subclasscheck__(self, cls):
return True


def _value_and_type_iter(parameters):
return ((p, type(p)) for p in parameters)


class _LiteralGenericAlias(_GenericAlias, _root=True):

def __eq__(self, other):
if not isinstance(other, _LiteralGenericAlias):
return NotImplemented

return set(_value_and_type_iter(self.__args__)) == set(_value_and_type_iter(other.__args__))
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def __hash__(self):
return hash(tuple(_value_and_type_iter(self.__args__)))


class Generic:
"""Abstract base class for generic types.
Expand Down
1 change: 1 addition & 0 deletions Misc/ACKS
Original file line number Diff line number Diff line change
Expand Up @@ -861,6 +861,7 @@ Jan Kanis
Rafe Kaplan
Jacob Kaplan-Moss
Allison Kaptur
Yurii Karabas
Janne Karila
Per Øyvind Karlsen
Anton Kasyanov
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Literal equality no longer depends on order of arguments. Patch provided by
Yurii Karabas.