# Plugin for mypy to support zope.interface
[](https://travis-ci.org/Shoobx/mypy-zope)
[](https://coveralls.io/github/Shoobx/mypy-zope)
[](http://mypy-lang.org/)
The goal is to be able to make zope interfaces to be treated as types in mypy
sense.
## Usage
Install both mypy and mypy-zope:
```sh
pip install mypy-zope
```
Edit `mypy.ini` file in your project to enable the plugin:
```ini
[mypy]
namespace_packages=True
plugins=mypy_zope:plugin
```
You're done! You can now check your project with mypy:
```sh
mypy your-project-dir
```
## What is supported?
You can browse
[sample files](https://github.com/Shoobx/mypy-zope/tree/master/tests/samples)
to get some sense on what features are supported and how they are handled.
### Interface declarations
You can define the interface and provide implementation:
```python
class IAnimal(zope.interface.Interface):
def say() -> None:
pass
@zope.interface.implementer(IAnimal)
class Cow(object):
def say(self) -> None:
print("Moooo")
animal: IAnimal = Cow()
animal.say()
```
The interface `IAnimal` will be treated as superclass of the implementation
`Cow`: you will be able to pass an implementation to functions accepting an
interface and all the usual polymorphism tricks.
It is also possible to declare the implementation using `classImplements`
function with the same effect as `@imlementer` decorator. This is useful if
you do not control the code that defines the implementation class.
```python
classImplements(Cow, IAnimal)
animal: IAnimal = Cow()
```
### Schema field type inference
A limited support for defining attributes as `zope.schema.Field`s is supported too:
```python
class IAnimal(zope.interface.Interface):
number_of_legs = zope.schema.Int(title="Number of legs")
@zope.interface.implementer(IAnimal)
class Cow(object):
number_of_legs = 4
```
In context of an interface, some known `zope.schema` field types are
automatically translated to python types, so the `number_of_legs` attributes is
getting the type `int` in the example above. That means mypy will report an
error if you try to assign string to that attribute on an instance of `IAnimal`
type. Custom fields or fields not recognized by plugin are given type `Any`.
### Field properties
Support for `zope.schema.FieldProperty` is limited, because type information is
not transferred from an interface to implementation attribute, but mypy doesn't
report errors on sources like this:
```python
class IAnimal(zope.interface.Interface):
number_of_legs = zope.schema.Int(title="Number of legs")
@zope.interface.implementer(IAnimal)
class Cow(object):
number_of_legs = zope.schema.FieldProperty(IAnimal['number_of_legs'])
```
The type of `Cow.number_of_legs` will become `Any` in this case, even though
`IAnimal.number_of_legs` would be inferred as `int`.
### Adaptation pattern
Zope interfaces can be "called" to lookup an adapter, like this:
```python
class IEUPowerSocket(zope.interface.Interface):
def fit():
pass
adapter = IEUPowerSocket(us_plug)
adapter.fit()
```
Type of the `adapter` variable will be set to `IEUPowerSocket`.
### Conditional type inference
When using `zope.interface`'s `implementedBy()` and `providedBy()` methods
in an if statement, `mypy` will know which type it is inside those statements.
```python
if IAnimal.providedBy(ob):
ob.number_of_legs += 2
```
### Declaration of overloaded methods in interfaces
Similarly to regular [overloaded
functions](https://docs.python.org/3/library/typing.html#typing.overload),
`@overload` declarations are supported in interfaces as well:
```python
class IAnimal(zope.interface.Interface):
@overload
def say() -> str:
...
@overload
def say(count: int) -> List[str]:
...
def say(count: int = None) -> Union[str, List[str]]:
pass
@zope.interface.implementer(IAnimal)
class Cow(object):
@overload
def say(self) -> str:
...
@overload
def say(self, count: int) -> List[str]:
...
def say(self, count: int = None) -> Union[str, List[str]]:
if count is None:
return "Mooo"
return ["Mooo"] * count
```
### Type stubs for zope.interface and zope.schema
`mypy-zope` ships with type stubs (`*.pyi` files) for `zope.interface` and
`zope.schema` packages. They are enabled automatically as soon as plugin is
enabled.
## What is not supported?
These `zope.interface` features are not supported:
* Declaring modules as interface implementers.
* Type inference for `zope.schema.List` and `zope.schema.Dict` fields.
* Stub files are largely incomplete
* Interface compatibility checker will not type-check non-method attributes
## Ready to use!
Currently, the project is used in production in various substantially large
projects and considered production-grade, however there still might be subtle
bugs around. Suggestions and pull requests are welcomed!
Raw data
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"description": "# Plugin for mypy to support zope.interface\n\n[](https://travis-ci.org/Shoobx/mypy-zope)\n[](https://coveralls.io/github/Shoobx/mypy-zope)\n[](http://mypy-lang.org/)\n\nThe goal is to be able to make zope interfaces to be treated as types in mypy\nsense.\n\n## Usage\n\nInstall both mypy and mypy-zope:\n```sh\npip install mypy-zope\n```\n\nEdit `mypy.ini` file in your project to enable the plugin:\n\n```ini\n[mypy]\nnamespace_packages=True\nplugins=mypy_zope:plugin\n```\n\nYou're done! You can now check your project with mypy:\n\n```sh\nmypy your-project-dir\n```\n\n## What is supported?\n\nYou can browse\n[sample files](https://github.com/Shoobx/mypy-zope/tree/master/tests/samples)\nto get some sense on what features are supported and how they are handled.\n\n### Interface declarations\n\nYou can define the interface and provide implementation:\n\n```python\nclass IAnimal(zope.interface.Interface):\n def say() -> None:\n pass\n\n@zope.interface.implementer(IAnimal)\nclass Cow(object):\n def say(self) -> None:\n print(\"Moooo\")\n\nanimal: IAnimal = Cow()\nanimal.say()\n```\n\nThe interface `IAnimal` will be treated as superclass of the implementation\n`Cow`: you will be able to pass an implementation to functions accepting an\ninterface and all the usual polymorphism tricks.\n\nIt is also possible to declare the implementation using `classImplements`\nfunction with the same effect as `@imlementer` decorator. 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