Plugins#
Litestar supports a plugin system that allows you to extend the functionality of the framework.
See also
Plugins are defined by protocols, and any type that satisfies a protocol can be included in the plugins argument of
the app.
The following plugin protocols are defined.
1. InitPluginProtocol: This protocol defines a contract for plugins
that can interact with the data that is used to instantiate the application instance.
2. SerializationPluginProtocol: This protocol defines
the contract for plugins that extend serialization functionality of the application.
InitPluginProtocol#
InitPluginProtocol defines an interface that allows for customization of the application’s initialization process.
Init plugins can define dependencies, add route handlers, configure middleware, and much more!
Implementations of these plugins must define a single method:
on_app_init(self, app_config: AppConfig) -> AppConfig:#
The method accepts and must return an AppConfig instance, which can be modified
and is later used to instantiate the application.
This method is invoked after any on_app_init hooks have been called, and each plugin is invoked in the order that
they are provided in the plugins argument of the app. Because of this, plugin
authors should make it clear in their documentation if their plugin should be invoked before or after other plugins.
Example#
The following example shows a simple plugin that adds a route handler, and a dependency to the application.
InitPluginProtocol implementation example#from typing import Dict
from litestar import Litestar, get
from litestar.config.app import AppConfig
from litestar.di import Provide
from litestar.plugins import InitPluginProtocol
@get("/", sync_to_thread=False)
def route_handler(name: str) -> Dict[str, str]:
return {"hello": name}
def get_name() -> str:
return "world"
class MyPlugin(InitPluginProtocol):
def on_app_init(self, app_config: AppConfig) -> AppConfig:
app_config.dependencies["name"] = Provide(get_name, sync_to_thread=False)
app_config.route_handlers.append(route_handler)
return app_config
app = Litestar(plugins=[MyPlugin()])
InitPluginProtocol implementation example#from litestar import Litestar, get
from litestar.config.app import AppConfig
from litestar.di import Provide
from litestar.plugins import InitPluginProtocol
@get("/", sync_to_thread=False)
def route_handler(name: str) -> dict[str, str]:
return {"hello": name}
def get_name() -> str:
return "world"
class MyPlugin(InitPluginProtocol):
def on_app_init(self, app_config: AppConfig) -> AppConfig:
app_config.dependencies["name"] = Provide(get_name, sync_to_thread=False)
app_config.route_handlers.append(route_handler)
return app_config
app = Litestar(plugins=[MyPlugin()])
Run it
> curl http://127.0.0.1:8000/
{"hello":"world"}
The MyPlugin class is an implementation of the InitPluginProtocol. It
defines a single method, on_app_init(), which takes an AppConfig instance
as an argument and returns same.
In the on_app_init() method, the dependency mapping is updated to include a new dependency named "name", which
is provided by the get_name() function, and route_handlers is updated to include the route_handler()
function. The modified AppConfig instance is then returned.
SerializationPluginProtocol#
The SerializationPluginProtocol defines a contract for plugins that provide serialization functionality for data types that are otherwise unsupported by the framework.
Implementations of these plugins must define the following methods.
supports_type(self, field_definition: FieldDefinition) -> bool:#
The method takes a FieldDefinition instance as an argument and returns a bool
indicating whether the plugin supports serialization for that type.
create_dto_for_type(self, field_definition: FieldDefinition) -> type[AbstractDTO]:#
This method accepts a FieldDefinition instance as an argument and must return a
AbstractDTO implementation that can be used to serialize and deserialize
the type.
During application startup, if a data or return annotation is encountered that is not a supported type, is supported by
the plugin, and doesn’t otherwise have a dto or return_dto defined, the plugin is used to create a DTO type for
that annotation.
Example#
The following example shows the actual implementation of the SerializationPluginProtocol for
SQLAlchemy models that is is provided in advanced_alchemy.
SerializationPluginProtocol implementation example#from __future__ import annotations
from advanced_alchemy.extensions.litestar.plugins import SQLAlchemySerializationPlugin
__all__ = ("SQLAlchemySerializationPlugin",)
supports_type(self, field_definition: FieldDefinition) -> bool:
returns a bool indicating whether the plugin supports serialization for the given type. Specifically, we return
True if the parsed type is either a collection of SQLAlchemy models or a single SQLAlchemy model.
create_dto_for_type(self, field_definition: FieldDefinition) -> type[AbstractDTO]:
takes a FieldDefinition instance as an argument and returns a
SQLAlchemyDTO subclass and includes some logic that may be
interesting to potential serialization plugin authors.
The first thing the method does is check if the parsed type is a collection of SQLAlchemy models or a single SQLAlchemy
model, retrieves the model type in either case and assigns it to the annotation variable.
The method then checks if annotation is already in the _type_dto_map dictionary. If it is, it returns the
corresponding DTO type. This is done to ensure that multiple SQLAlchemyDTO
subtypes are not created for the same model.
If the annotation is not in the _type_dto_map dictionary, the method creates a new DTO type for the annotation,
adds it to the _type_dto_map dictionary, and returns it.
DIPlugin#
DIPlugin can be used to extend Litestar’s dependency
injection by providing information about injectable types.
Its main purpose it to facilitate the injection of callables with unknown signatures,
for example Pydantic’s BaseModel classes; These are not supported natively since,
while they are callables, their type information is not contained within their callable
signature (their __init__() method).
from inspect import Parameter, Signature
from typing import Any, Dict, Tuple
from litestar import Litestar, get
from litestar.di import Provide
from litestar.plugins import DIPlugin
class MyBaseType:
def __init__(self, param):
self.param = param
class MyDIPlugin(DIPlugin):
def has_typed_init(self, type_: Any) -> bool:
return issubclass(type_, MyBaseType)
def get_typed_init(self, type_: Any) -> Tuple[Signature, Dict[str, Any]]:
signature = Signature([Parameter(name="param", kind=Parameter.POSITIONAL_OR_KEYWORD)])
annotations = {"param": str}
return signature, annotations
@get("/", dependencies={"injected": Provide(MyBaseType, sync_to_thread=False)})
async def handler(injected: MyBaseType) -> str:
return injected.param
app = Litestar(route_handlers=[handler], plugins=[MyDIPlugin()])
from inspect import Parameter, Signature
from typing import Any
from litestar import Litestar, get
from litestar.di import Provide
from litestar.plugins import DIPlugin
class MyBaseType:
def __init__(self, param):
self.param = param
class MyDIPlugin(DIPlugin):
def has_typed_init(self, type_: Any) -> bool:
return issubclass(type_, MyBaseType)
def get_typed_init(self, type_: Any) -> tuple[Signature, dict[str, Any]]:
signature = Signature([Parameter(name="param", kind=Parameter.POSITIONAL_OR_KEYWORD)])
annotations = {"param": str}
return signature, annotations
@get("/", dependencies={"injected": Provide(MyBaseType, sync_to_thread=False)})
async def handler(injected: MyBaseType) -> str:
return injected.param
app = Litestar(route_handlers=[handler], plugins=[MyDIPlugin()])
Run it
> curl http://127.0.0.1:8000/?param=hello
hello