# sphinx-autodoc-typehints

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This extension allows you to use Python 3 annotations for documenting acceptable argument types and return value types
of functions. See an example of the Sphinx render at the
[pyproject-api docs](https://pyproject-api.readthedocs.io/en/latest/).

This allows you to use type hints in a very natural fashion, allowing you to migrate from this:

```python
def format_unit(value, unit):
    """
    Formats the given value as a human readable string using the given units.

    :param float|int value: a numeric value
    :param str unit: the unit for the value (kg, m, etc.)
    :rtype: str
    """
    return f"{value} {unit}"
```

to this:

```python
from typing import Union


def format_unit(value: Union[float, int], unit: str) -> str:
    """
    Formats the given value as a human readable string using the given units.

    :param value: a numeric value
    :param unit: the unit for the value (kg, m, etc.)
    """
    return f"{value} {unit}"
```

## Installation and setup

First, use pip to download and install the extension:

```bash
pip install sphinx-autodoc-typehints
```

Then, add the extension to your `conf.py`:

```python
extensions = ["sphinx.ext.autodoc", "sphinx_autodoc_typehints"]
```

## Options

The following configuration options are accepted:

- `typehints_fully_qualified` (default: `False`): if `True`, class names are always fully qualified (e.g.
  `module.for.Class`). If `False`, just the class name displays (e.g. `Class`)
- `always_document_param_types` (default: `False`): If `False`, do not add type info for undocumented parameters. If
  `True`, add stub documentation for undocumented parameters to be able to add type info.
- `typehints_document_rtype` (default: `True`): If `False`, never add an `:rtype:` directive. If `True`, add the
  `:rtype:` directive if no existing `:rtype:` is found.
- `typehints_use_rtype` (default: `True`): Controls behavior when `typehints_document_rtype` is set to `True`. If
  `True`, document return type in the `:rtype:` directive. If `False`, document return type as part of the `:return:`
  directive, if present, otherwise fall back to using `:rtype:`. Use in conjunction with
  [napoleon_use_rtype](https://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html#confval-napoleon_use_rtype)
  to avoid generation of duplicate or redundant return type information.
- `typehints_defaults` (default: `None`): If `None`, defaults are not added. Otherwise, adds a default annotation:

  - `'comma'` adds it after the type, changing Sphinx’ default look to “**param** (_int_, default: `1`) -- text”.
  - `'braces'` adds `(default: ...)` after the type (useful for numpydoc like styles).
  - `'braces-after'` adds `(default: ...)` at the end of the parameter documentation text instead.

- `simplify_optional_unions` (default: `True`): If `True`, optional parameters of type \"Union\[\...\]\" are simplified
  as being of type Union\[\..., None\] in the resulting documentation (e.g. Optional\[Union\[A, B\]\] -\> Union\[A, B,
  None\]). If `False`, the \"Optional\"-type is kept. Note: If `False`, **any** Union containing `None` will be
  displayed as Optional! Note: If an optional parameter has only a single type (e.g Optional\[A\] or Union\[A, None\]),
  it will **always** be displayed as Optional!
- `typehints_formatter` (default: `None`): If set to a function, this function will be called with `annotation` as first
  argument and `sphinx.config.Config` argument second. The function is expected to return a string with reStructuredText
  code or `None` to fall back to the default formatter.

## How it works

The extension listens to the `autodoc-process-signature` and `autodoc-process-docstring` Sphinx events. In the former,
it strips the annotations from the function signature. In the latter, it injects the appropriate `:type argname:` and
`:rtype:` directives into the docstring.

Only arguments that have an existing `:param:` directive in the docstring get their respective `:type:` directives
added. The `:rtype:` directive is added if and only if no existing `:rtype:` is found.

## Compatibility with sphinx.ext.napoleon

To use [sphinx.ext.napoleon](http://www.sphinx-doc.org/en/stable/ext/napoleon.html) with sphinx-autodoc-typehints, make
sure you load [sphinx.ext.napoleon](http://www.sphinx-doc.org/en/stable/ext/napoleon.html) first, **before**
sphinx-autodoc-typehints. See [Issue 15](https://github.com/agronholm/sphinx-autodoc-typehints/issues/15) on the issue
tracker for more information.

## Dealing with circular imports

Sometimes functions or classes from two different modules need to reference each other in their type annotations. This
creates a circular import problem. The solution to this is the following:

1. Import only the module, not the classes/functions from it
2. Use forward references in the type annotations (e.g. `def methodname(self, param1: 'othermodule.OtherClass'):`)

On Python 3.7, you can even use `from __future__ import annotations` and remove the quotes.

## Using type hint comments

If you\'re documenting code that needs to stay compatible with Python 2.7, you cannot use regular type annotations.
Instead, you must either be using Python 3.8 or later or have [typed_ast](https://pypi.org/project/typed-ast/)
installed. The package extras `type_comments` will pull in the appropriate dependencies automatically. Then you can add
type hint comments in the following manner:

```python
def myfunction(arg1, arg2):
    # type: (int, str) -> int
    return 42
```

or alternatively:

```python
def myfunction(
    arg1,  # type: int
    arg2,  # type: str
):
    # type: (...) -> int
    return 42
```
