https://github.com/hauntsaninja/no_implicit_optional

A codemod to make your implicit optional type hints PEP 484 compliant.
https://github.com/hauntsaninja/no_implicit_optional

Last synced: 13 days ago
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A codemod to make your implicit optional type hints PEP 484 compliant.

• Host: GitHub
• URL: https://github.com/hauntsaninja/no_implicit_optional
• Owner: hauntsaninja
• License: mit
• Created: 2022-09-07T04:00:26.000Z (about 2 years ago)
• Default Branch: master
• Last Pushed: 2023-11-25T23:21:36.000Z (12 months ago)
• Last Synced: 2024-10-13T23:13:22.840Z (26 days ago)
• Language: Python
• Size: 10.7 KB
• Stars: 78
• Watchers: 3
• Forks: 8
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-python-typing - no_implicit_optional - A codemod to make your implicit optional type hints [PEP 484](https://peps.python.org/pep-0484/#union-types) compliant. (Tools / Helper tools to add annotations to existing code)

README

        
# no_implicit_optional

A codemod to make your implicit optional type hints PEP 484 compliant.

## Running

This tool will make changes to your code. Make sure you're using version control, like `git`.

```bash

pipx run no_implicit_optional 

```

Alternatively, and perhaps more familiarly:

```bash

pip install no_implicit_optional

no_implicit_optional 

```

To make this tool use PEP 604 `X | None` syntax instead of `Optional[X]`, use the

`--use-union-or` flag. Note that this syntax is only fully supported on Python 3.10 and newer.

## What's going on?

By default, mypy 0.982 and earlier allowed eliding `Optional` for arguments with default values of

`None`. From experience, this was found to be a source of confusion and bugs.

In 2018, PEP 484 was updated to require the explicit use of `Optional` (or a `Union` with `None`)

and mypy enforces this when run using `mypy --strict` or `mypy --no-implicit-optional`.

Similarly, other type checkers like pyright do not recognise implicit `Optional` at all.

Here's what this looks like in practice:

```python

def bad(x: int = None):

    ...

def good(x: Optional[int] = None):

    ...

def good(x: Union[int, None] = None):

    ...

# PEP 604 syntax, requires Python 3.10+ or `from __future__ import annotations`

def good(x: int | None = None):

    ...

```

Anyway, mypy is changing its default to match PEP 484 and disallow implicit `Optional`. In order

to make the transition easier, this tool will try to automatically fix your code, building off

of [libcst](https://libcst.readthedocs.io/en/latest/) to do so.

Also refer to:

- https://peps.python.org/pep-0484/#union-types

- https://github.com/python/mypy/issues/9091

- https://github.com/python/mypy/pull/13401

## I don't want to change my code

Use `mypy --implicit-optional` or set `implicit_optional = True` in your mypy config.