74 lines
2.1 KiB
Plaintext
74 lines
2.1 KiB
Plaintext
This rule raises an issue when the name of a local variable matches the name of a builtin.
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== Why is this an issue?
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Defining a variable with the same name as a built-in symbol will "shadow" it. That means that the builtin will no longer be accessible through its original name, having locally been replaced by the variable.
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Shadowing a builtin makes the code more difficult to read and maintain. It may also be a source of bugs as you can reference the builtin by mistake.
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It is sometimes acceptable to shadow a builtin to improve the readability of a public API or to support multiple versions of a library. In these cases, benefits are greater than the maintainability cost. This should, however, be done with care.
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It is generally not a good practice to shadow builtins with variables which are local to a function or method. These variables are not public and can easily be renamed, thus reducing the confusion and making the code less error-prone.
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=== Code examples
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==== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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def a_function():
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int = 42 # Noncompliant; int is a builtin
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----
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==== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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def a_function():
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value = 42
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----
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== Resources
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=== Documentation
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* Python documentation - https://docs.python.org/3.8/library/stdtypes.html[Built-in Types]
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* Python documentation - https://docs.python.org/3/library/functions.html[Built-in Functions]
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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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Rename this variable; it shadows a builtin.
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=== Highlighting
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Primary:
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* The first definition of a variable shadowing a builtin in a local scope (function)
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Secondary:
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* Any other assignment to the variable.
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* message: "Variable also assigned here."
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'''
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== Comments And Links
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(visible only on this page)
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=== relates to: S2137
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=== on 30 Apr 2020, 19:12:03 Nicolas Harraudeau wrote:
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This rule is similar to RSPEC-2137 but it is a code smell because shadowing builtins will not make your code crash most of the time.
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endif::env-github,rspecator-view[]
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