c70acb68e9
You can preview this rule [here](https://sonarsource.github.io/rspec/#/rspec/S6792/python) (updated a few minutes after each push). ## Review A dedicated reviewer checked the rule description successfully for: - [ ] logical errors and incorrect information - [ ] information gaps and missing content - [ ] text style and tone - [ ] PR summary and labels follow [the guidelines](https://github.com/SonarSource/rspec/#to-modify-an-existing-rule) --------- Co-authored-by: guillaume-dequenne-sonarsource <guillaume-dequenne-sonarsource@users.noreply.github.com> Co-authored-by: Guillaume Dequenne <guillaume.dequenne@sonarsource.com>
84 lines
2.5 KiB
Plaintext
84 lines
2.5 KiB
Plaintext
This rule raises an issue when a generic class is defined through explicit inheritance of `typing.Generic` instead of using the type parameter syntax.
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== Why is this an issue?
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Through https://peps.python.org/pep-0695/[PEP 695], Python 3.12 introduces the type parameter syntax to allow for a more compact and explicit way to define generic classes and functions.
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Prior to Python 3.12, defining a generic class would be done through the following syntax:
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[source,python]
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----
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from typing import Generic, TypeVar
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_T_co = TypeVar("_T_co", covariant=True, bound=str)
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class ClassA(Generic[_T_co]):
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def method1(self) -> _T_co:
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...
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----
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Since Python 3.12, it can be done with the following syntax:
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[source,python]
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----
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class ClassA[T: str]:
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def method1(self) -> T:
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...
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----
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Using the former syntax requires importing `TypeVar` and `Generic` symbols from the `typing` module. It also requires the explicit definition of a type variable in the global scope, with a redundant name provided in quotes (`T = TypeVar("T")`). This makes the definition of generic classes verbose and confusing.
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It is therefore recommended to use the type parameter syntax when working with Python 3.12 and later.
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=== Exceptions
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This rule will only raise an issue when the Python version of the analyzed project is set to 3.12 or higher.
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== How to fix it
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To fix this issue, make sure to use the type parameter syntax whenever defining a generic class.
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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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from typing import Generic, TypeVar
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_T_co = TypeVar("_T_co", covariant=True, bound=str)
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class ClassA(Generic[_T_co]): # Noncompliant: Explicit definition of a TypeVar and inheritance from typing.Generic is verbose
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def method1(self) -> _T_co:
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...
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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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class ClassA[T: str]: # Compliant: Concise syntax for type parameter is used
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def method1(self) -> T:
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...
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----
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== Resources
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=== Documentation
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* Python Documentation - https://docs.python.org/3.12/reference/compound_stmts.html#generic-classes[Generic classes]
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* Python 3.12 Release Notes - https://docs.python.org/3.12/whatsnew/3.12.html#pep-695-type-parameter-syntax[PEP 695: Type Parameter Syntax]
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* PEP 695 - https://peps.python.org/pep-0695/[Type Parameter Syntax]
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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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Use the type parameter syntax to declare this generic class.
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'''
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endif::env-github,rspecator-view[]
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