Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/hypothesis/strategies/_internal/misc.py: 67%

1# This file is part of Hypothesis, which may be found at 

2# https://github.com/HypothesisWorks/hypothesis/ 

3# 

4# Copyright the Hypothesis Authors. 

5# Individual contributors are listed in AUTHORS.rst and the git log. 

6# 

7# This Source Code Form is subject to the terms of the Mozilla Public License, 

8# v. 2.0. If a copy of the MPL was not distributed with this file, You can 

9# obtain one at https://mozilla.org/MPL/2.0/. 

10 

11from collections.abc import Callable 

12from typing import Any, Never, NoReturn 

13 

14from hypothesis.errors import CannotInvert 

15from hypothesis.internal.conjecture.choice import ChoiceT 

16from hypothesis.internal.conjecture.data import ConjectureData 

17from hypothesis.internal.conjecture.junkdrawer import equal_values 

18from hypothesis.internal.reflection import get_pretty_function_description 

19from hypothesis.strategies._internal.strategies import ( 

20 Ex, 

21 RecurT, 

22 SampledFromStrategy, 

23 SearchStrategy, 

24 T, 

25 is_hashable, 

26) 

27from hypothesis.strategies._internal.utils import cacheable, defines_strategy 

28from hypothesis.utils.conventions import UniqueIdentifier 

29 

30 

31class JustStrategy(SampledFromStrategy[Ex]): 

32 """A strategy which always returns a single fixed value. 

33 

34 It's implemented as a length-one SampledFromStrategy so that all our 

35 special-case logic for filtering and sets applies also to just(x). 

36 

37 The important difference from a SampledFromStrategy with only one 

38 element to choose is that JustStrategy *never* touches the underlying 

39 choice sequence, i.e. drawing neither reads from nor writes to `data`. 

40 This is a reasonably important optimisation (or semantic distinction!) 

41 for both JustStrategy and SampledFromStrategy. 

42 """ 

43 

44 @property 

45 def value(self) -> Ex: 

46 return self.elements[0] 

47 

48 def __repr__(self) -> str: 

49 suffix = "".join( 

50 f".{name}({get_pretty_function_description(f)})" 

51 for name, f, _ in self._transformations 

52 ) 

53 if self.value is None: 

54 return "none()" + suffix 

55 return f"just({get_pretty_function_description(self.value)}){suffix}" 

56 

57 def calc_is_cacheable(self, recur: RecurT) -> bool: 

58 return is_hashable(self.value) 

59 

60 def do_filtered_draw(self, data: ConjectureData) -> Ex | UniqueIdentifier: 

61 # The parent class's `do_draw` implementation delegates directly to 

62 # `do_filtered_draw`, which we can greatly simplify in this case since 

63 # we have exactly one value. (This also avoids drawing any data.) 

64 return self._transform(self.value, data=data) 

65 

66 def _invert(self, value: Any) -> tuple[ChoiceT, ...]: 

67 if not equal_values(self._transform(self.value, data=None), value): 

68 raise CannotInvert(f"{value!r} is not produced by {self!r}") 

69 return () 

70 

71 

72@defines_strategy(eager=True) 

73def just(value: T) -> SearchStrategy[T]: 

74 """Return a strategy which only generates ``value``. 

75 

76 Note: ``value`` is not copied. Be wary of using mutable values. 

77 

78 If ``value`` is the result of a callable, you can use 

79 :func:`builds(callable) <hypothesis.strategies.builds>` instead 

80 of ``just(callable())`` to get a fresh value each time. 

81 

82 Examples from this strategy do not shrink (because there is only one). 

83 """ 

84 return JustStrategy([value]) 

85 

86 

87@defines_strategy(force_reusable_values=True) 

88def none() -> SearchStrategy[None]: 

89 """Return a strategy which only generates None. 

90 

91 Examples from this strategy do not shrink (because there is only 

92 one). 

93 """ 

94 return just(None) 

95 

96 

97class Nothing(SearchStrategy["Never"]): 

98 def calc_is_empty(self, recur: RecurT) -> bool: 

99 return True 

100 

101 def do_draw(self, data: ConjectureData) -> NoReturn: 

102 # This method should never be called because draw() will mark the 

103 # data as invalid immediately because is_empty is True. 

104 raise NotImplementedError("This should never happen") 

105 

106 def calc_has_reusable_values(self, recur: RecurT) -> bool: 

107 return True 

108 

109 def __repr__(self) -> str: 

110 return "nothing()" 

111 

112 def map(self, pack: Callable[[Any], Any]) -> SearchStrategy["Never"]: 

113 return self 

114 

115 def filter(self, condition: Callable[[Any], Any]) -> "SearchStrategy[Never]": 

116 return self 

117 

118 def flatmap( 

119 self, expand: Callable[[Any], "SearchStrategy[Any]"] 

120 ) -> "SearchStrategy[Never]": 

121 return self 

122 

123 

124NOTHING = Nothing() 

125 

126 

127@cacheable 

128@defines_strategy(eager=True) 

129def nothing() -> SearchStrategy["Never"]: 

130 """This strategy never successfully draws a value and will always reject on 

131 an attempt to draw. 

132 

133 Examples from this strategy do not shrink (because there are none). 

134 """ 

135 return NOTHING 

136 

137 

138class BooleansStrategy(SearchStrategy[bool]): 

139 def do_draw(self, data: ConjectureData) -> bool: 

140 return data.draw_boolean() 

141 

142 def _invert(self, value: Any) -> tuple[ChoiceT, ...]: 

143 if not isinstance(value, bool): 

144 raise CannotInvert(f"{value!r} is not a bool") 

145 return (value,) 

146 

147 def __repr__(self) -> str: 

148 return "booleans()"