16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
117 lines
3.3 KiB
Plaintext
117 lines
3.3 KiB
Plaintext
== Why is this an issue?
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:link-with-uscores1: https://docs.python.org/3/reference/datamodel.html#object.__getitem__
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:link-with-uscores2: https://docs.python.org/3/reference/datamodel.html#object.__class_getitem__
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:link-with-uscores3: https://docs.python.org/3/reference/datamodel.html#object.__setitem__
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:link-with-uscores4: https://docs.python.org/3/reference/datamodel.html#object.__delitem__
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Getting, setting and deleting items using square brackets requires the accessed object to have special methods:
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* Getting items such as ``++my_variable[key]++`` requires ``++my_variable++`` to have the {link-with-uscores1}[``++__getitem__++``] method, or the {link-with-uscores2}[``++__class_getitem__++``] method if ``++my_variable++`` is a class.
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* Setting items such as ``++my_variable[key] = 42++`` requires ``++my_variable++`` to have the {link-with-uscores3}[``++__setitem__++``] method.
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* Deleting items such as ``++del my_variable[key]++`` requires ``++my_variable++`` to have the {link-with-uscores4}[``++__delitem__++``] method.
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This rule raises an issue when an item operation is performed on an object which doesn't have the corresponding method.
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=== Noncompliant code example
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[source,python]
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----
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del (1, 2)[0] # Noncompliant, tuples are immutable
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(1, 2)[0] = 42 # Noncompliant
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(1, 2)[0]
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class A:
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def __init__(self, values):
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self._values = values
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a = A([0,1,2])
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a[0] # Noncompliant
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del a[0] # Noncompliant
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a[0] = 42 # Noncompliant
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class B:
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pass
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B[0] # Noncompliant
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----
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=== Compliant solution
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[source,python]
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----
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del [1, 2][0] # Lists are mutable
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[1, 2][0] = 42
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[1, 2][0]
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class A:
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def __init__(self, values):
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self._values = values
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def __getitem__(self, key):
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return self._values[key]
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def __setitem__(self, key, value):
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self._values[key] = value
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def __delitem__(self, key):
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del self._values[key]
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a = A([0,1,2])
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a[0]
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del a[0]
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a[0] = 42
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class B:
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def __class_getitem__(cls, key):
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return [0, 1, 2, 3][key]
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B[0]
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----
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:link-with-uscores1: https://docs.python.org/3/reference/datamodel.html#object.__getitem__
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:link-with-uscores2: https://docs.python.org/3/reference/datamodel.html#object.__setitem__
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:link-with-uscores3: https://docs.python.org/3/reference/datamodel.html#object.__delitem__
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:link-with-uscores4: https://docs.python.org/3/reference/datamodel.html#object.__class_getitem__
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== Resources
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* {link-with-uscores1}[Python documentation - ++__getitem__++ method]
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* {link-with-uscores2}[Python documentation - ++__setitem__++ method]
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* {link-with-uscores3}[Python documentation - ++__delitem__++ method]
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* {link-with-uscores4}[Python documentation - ++__class_getitem__++ method]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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* Fix this code; "X" does not have a "__getitem__" method.
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* Fix this code; "X" does not have a "__setitem__" method.
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* Fix this code; "X" does not have a "__delitem__" method.
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* Fix this code; class "Y" does not have a "__class_getitem__" method.
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=== Highlighting
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Primary: The variable before the "["
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* Secondary 1 (if the call is made on a variable)
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** location: The last value assigned.
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** message: "Assigned value."
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* Secondary 2
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** location: The class/function/... definition
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** message: 'Definition of \"``++X++``".'
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endif::env-github,rspecator-view[]
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