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https://github.com/sco1/flake8-annotations

Flake8 Type Annotation Checking
https://github.com/sco1/flake8-annotations

flake8 flake8-plugin python python3 type-annotations

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Flake8 Type Annotation Checking

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README 

        
# flake8-annotations

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`flake8-annotations` is a plugin for [Flake8](http://flake8.pycqa.org/en/latest/) that detects the absence of [PEP 3107-style](https://www.python.org/dev/peps/pep-3107/) function annotations.



What this won't do: replace [mypy](http://mypy-lang.org/), check type comments (see: [PEP 484](https://peps.python.org/pep-0484/#type-comments)), check variable annotations (see: [PEP 526](https://www.python.org/dev/peps/pep-0526/)), or respect stub files.



## Installation

Install from PyPi with your favorite `pip` invocation:



```bash

$ pip install flake8-annotations

```



It will then be run automatically as part of flake8.



You can verify it's being picked up by invoking the following in your shell:



```bash

$ flake8 --version

6.1.0 (flake8-annotations: 3.0.1, mccabe: 0.7.0, pycodestyle: 2.11.1, pyflakes: 3.1.0) CPython 3.12.0 on Darwin

```



## Table of Warnings

With the exception of `ANN4xx`-level warnings, all warnings are enabled by default.



### Function Annotations

| ID       | Description                                   |

|----------|-----------------------------------------------|

| `ANN001` | Missing type annotation for function argument |

| `ANN002` | Missing type annotation for `*args`           |

| `ANN003` | Missing type annotation for `**kwargs`        |



### Method Annotations

| ID       | Description                                                  |

|----------|--------------------------------------------------------------|

| `ANN101` | Missing type annotation for `self` in method1     |

| `ANN102` | Missing type annotation for `cls` in classmethod1 |



### Return Annotations

| ID       | Description                                           |

|----------|-------------------------------------------------------|

| `ANN201` | Missing return type annotation for public function    |

| `ANN202` | Missing return type annotation for protected function |

| `ANN203` | Missing return type annotation for secret function    |

| `ANN204` | Missing return type annotation for special method     |

| `ANN205` | Missing return type annotation for staticmethod       |

| `ANN206` | Missing return type annotation for classmethod        |



### Opinionated Warnings

These warnings are disabled by default.

| ID       | Description                                                             |

|----------|-------------------------------------------------------------------------|

| `ANN401` | Dynamically typed expressions (typing.Any) are disallowed2,3 |

| `ANN402` | Type comments are disallowed3                                |



Use [`extend-select`](https://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-extend-ignore) to enable opinionated warnings without overriding other implicit configurations4.



**Notes:**

1. See: [PEP 484](https://www.python.org/dev/peps/pep-0484/#annotating-instance-and-class-methods) and [PEP 563](https://www.python.org/dev/peps/pep-0563/) for suggestions on annotating `self` and `cls` arguments

2. See: [Dynamic Typing Caveats](#dynamic-typing-caveats)

3. Only function declarations are considered by this plugin; type annotations in function/module bodies are not checked 

4. Common pitfall: the use of [`ignore`](https://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-ignore) will enable all implicitly disabled warnings



## Configuration Options

Some opinionated flags are provided to tailor the linting errors emitted.



### `--suppress-none-returning`: `bool`

Suppress `ANN200`-level errors for functions that meet one of the following criteria:

  * Contain no `return` statement, or

  * Explicit `return` statement(s) all return `None` (explicitly or implicitly).



Default: `False`



### `--suppress-dummy-args`: `bool`

Suppress `ANN000`-level errors for dummy arguments, defined as `_`.



Default: `False`



### `--allow-untyped-defs`: `bool`

Suppress all errors for dynamically typed functions. A function is considered dynamically typed if it does not contain any type hints.



Default: `False`



### `--allow-untyped-nested`: `bool`

Suppress all errors for dynamically typed nested functions. A function is considered dynamically typed if it does not contain any type hints.



Default: `False`



### `--mypy-init-return`: `bool`

Allow omission of a return type hint for `__init__` if at least one argument is annotated. See [mypy's documentation](https://mypy.readthedocs.io/en/stable/class_basics.html?#annotating-init-methods) for additional details.



Default: `False`



### `--dispatch-decorators`: `list[str]`

Comma-separated list of decorators flake8-annotations should consider as dispatch decorators. Linting errors are suppressed for functions decorated with at least one of these functions.



Decorators are matched based on their attribute name. For example, `"singledispatch"` will match any of the following:

  * `import functools; @functools.singledispatch`

  * `import functools as ; @.singledispatch`

  * `from functools import singledispatch; @singledispatch`



**NOTE:** Deeper imports, such as `a.b.singledispatch` are not supported.



See: [Generic Functions](#generic-functions) for additional information.



Default: `"singledispatch, singledispatchmethod"`



### `--overload-decorators`: `list[str]`

Comma-separated list of decorators flake8-annotations should consider as [`typing.overload`](https://docs.python.org/3/library/typing.html#typing.overload) decorators.



Decorators are matched based on their attribute name. For example, `"overload"` will match any of the following:

  * `import typing; @typing.overload`

  * `import typing as ; @.overload`

  * `from typing import overload; @overload`



**NOTE:** Deeper imports, such as `a.b.overload` are not supported.



See: [The `typing.overload` Decorator](#the-typingoverload-decorator) for additional information.



Default: `"overload"`



### `--allow-star-arg-any`

Suppress `ANN401` for dynamically typed `*args` and `**kwargs`.



Default: `False`



## Generic Functions

Per the Python Glossary, a [generic function](https://docs.python.org/3/glossary.html#term-generic-function) is defined as:



> A function composed of multiple functions implementing the same operation for different types. Which implementation should be used during a call is determined by the dispatch algorithm.



In the standard library we have some examples of decorators for implementing these generic functions: [`functools.singledispatch`](https://docs.python.org/3/library/functools.html#functools.singledispatch) and [`functools.singledispatchmethod`](https://docs.python.org/3/library/functools.html#functools.singledispatchmethod). In the spirit of the purpose of these decorators, errors for missing annotations for functions decorated with at least one of these are ignored.



For example, this code:



```py

import functools



@functools.singledispatch

def foo(a):

    print(a)



@foo.register

def _(a: list) -> None:

    for idx, thing in enumerate(a):

        print(idx, thing)

```



Will not raise any linting errors for `foo`.



Decorator(s) to treat as defining generic functions may be specified by the [`--dispatch-decorators`](#--dispatch-decorators-liststr) configuration option.



## The `typing.overload` Decorator

Per the [`typing`](https://docs.python.org/3/library/typing.html#typing.overload) documentation:



> The `@overload` decorator allows describing functions and methods that support multiple different combinations of argument types. A series of `@overload`-decorated definitions must be followed by exactly one non-`@overload`-decorated definition (for the same function/method).



In the spirit of the purpose of this decorator, errors for missing annotations for non-`@overload`-decorated functions are ignored if they meet this criteria.



For example, this code:



```py

import typing



@typing.overload

def foo(a: int) -> int:

    ...



def foo(a):

    ...

```



Will not raise linting errors for missing annotations for the arguments & return of the non-decorated `foo` definition.



Decorator(s) to treat as `typing.overload` may be specified by the [`--overload-decorators`](#--overload-decorators-liststr) configuration option.



## Dynamic Typing Caveats

Support is only provided for the following patterns:

  * `from typing import any; foo: Any`

  * `import typing; foo: typing.Any`

  * `import typing as ; foo: .Any`



Nested dynamic types (e.g. `typing.Tuple[typing.Any]`) and redefinition (e.g. `from typing import Any as Foo`) will not be identified.



## Contributing



### Development Environment

This project uses [Poetry](https://python-poetry.org/) to manage dependencies. With your fork cloned to your local machine, you can install the project and its dependencies to create a development environment using:



```bash

$ poetry install

```



Note: An editable installation of `flake8-annotations` in the developer environment is required in order for the plugin to be registered for Flake8. By default, Poetry includes an editable install of the project itself when `poetry install` is invoked.



A [pre-commit](https://pre-commit.com) configuration is also provided to create a pre-commit hook so linting errors aren't committed:



```bash

$ pre-commit install

```



### Testing & Coverage

A [pytest](https://docs.pytest.org/en/latest/) suite is provided, with coverage reporting from [pytest-cov](https://github.com/pytest-dev/pytest-cov). A [tox](https://github.com/tox-dev/tox/) configuration is provided to test across all supported versions of Python. Testing will be skipped for Python versions that cannot be found.



```bash

$ tox

```



Details on missing coverage, including in the test suite, is provided in the report to allow the user to generate additional tests for full coverage.