✨ Add reference (code API) docs with PEP 727, add subclass with custom docstrings for BackgroundTasks, refactor docs structure (#10392)

* ➕ Add mkdocstrings and griffe-typingdoc to dependencies

* 🔧 Add mkdocstrings configs to MkDocs

* 📝 Add first WIP reference page

* ⬆️ Upgrade typing-extensions to the minimum version including Doc()

* 📝 Add docs to FastAPI parameters

* 📝 Add docstrings for OpenAPI docs utils

* 📝 Add docstrings for security utils

* 📝 Add docstrings for UploadFile

* 📝 Update docstrings in FastAPI class

* 📝 Add docstrings for path operation methods

* 📝 Add docstring for jsonable_encoder

* 📝 Add docstrings for exceptions

* 📝 Add docstsrings for parameter functions

* 📝 Add docstrings for responses

* 📝 Add docstrings for APIRouter

* ♻️ Sub-class BackgroundTasks to document it with docstrings

* 📝 Update usage of background tasks in dependencies

* ✅ Update tests with new deprecation warnings

* 📝 Add new reference docs

* 🔧 Update MkDocs with new reference docs

* ✅ Update pytest fixture, deprecation is raised only once

* 🎨 Update format for types in exceptions.py

* ♻️ Update annotations in BackgroundTask, `Annotated` can't take ParamSpec's P.args or P.kwargs

* ✏️ Fix typos caught by @pawamoy

* 🔧 Update and fix MkDocstrings configs from @pawamoy tips

* 📝 Update reference docs

* ✏️ Fix typos found by @pawamoy

* ➕ Add HTTPX as a dependency for docs, for the TestClient

* 🔧 Update MkDocs config, rename websockets reference

* 🔇 Add type-ignores for Doc as the stubs haven't been released for mypy

* 🔥 Remove duplicated deprecated notice

* 🔇 Remove typing error for unreleased stub in openapi/docs.py

* ✅ Add tests for UploadFile for coverage

* ⬆️ Upgrade griffe-typingdoc==0.2.2

* 📝 Refactor docs structure

* 🔨 Update README generation with new index frontmatter and style

* 🔨 Update generation of languages, remove from top menu, keep in lang menu

* 📝 Add OpenAPI Pydantic models

* 🔨 Update docs script to not translate Reference and Release Notes

* 🔧 Add reference for OpenAPI models

* 🔧 Update MkDocs config for mkdocstrings insiders

* 👷 Install mkdocstring insiders in CI for docs

* 🐛 Fix MkDocstrings insiders install URL

* ➕ Move dependencies shared by docs and tests to its own requirements file

* 👷 Update cache keys for test and docs dependencies

* 📝 Remove no longer needed __init__ placeholder docstrings

* 📝 Move docstring for APIRouter to the class level (not __init__ level)

* 🔥 Remove no longer needed dummy placeholder __init__ docstring

fastapi/exceptions.py

@@ -1,20 +1,141 @@
-from typing import Any, Dict, Optional, Sequence, Type
+from typing import Any, Dict, Optional, Sequence, Type, Union
 
 from pydantic import BaseModel, create_model
 from starlette.exceptions import HTTPException as StarletteHTTPException
-from starlette.exceptions import WebSocketException as WebSocketException  # noqa: F401
+from starlette.exceptions import WebSocketException as StarletteWebSocketException
+from typing_extensions import Annotated, Doc  # type: ignore [attr-defined]
 
 
 class HTTPException(StarletteHTTPException):
+    """
+    An HTTP exception you can raise in your own code to show errors to the client.
+
+    This is for client errors, invalid authentication, invalid data, etc. Not for server
+    errors in your code.
+
+    Read more about it in the
+    [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/).
+
+    ## Example
+
+    ```python
+    from fastapi import FastAPI, HTTPException
+
+    app = FastAPI()
+
+    items = {"foo": "The Foo Wrestlers"}
+
+
+    @app.get("/items/{item_id}")
+    async def read_item(item_id: str):
+        if item_id not in items:
+            raise HTTPException(status_code=404, detail="Item not found")
+        return {"item": items[item_id]}
+    ```
+    """
+
     def __init__(
         self,
-        status_code: int,
-        detail: Any = None,
-        headers: Optional[Dict[str, str]] = None,
+        status_code: Annotated[
+            int,
+            Doc(
+                """
+                HTTP status code to send to the client.
+                """
+            ),
+        ],
+        detail: Annotated[
+            Any,
+            Doc(
+                """
+                Any data to be sent to the client in the `detail` key of the JSON
+                response.
+                """
+            ),
+        ] = None,
+        headers: Annotated[
+            Optional[Dict[str, str]],
+            Doc(
+                """
+                Any headers to send to the client in the response.
+                """
+            ),
+        ] = None,
     ) -> None:
         super().__init__(status_code=status_code, detail=detail, headers=headers)
 
 
+class WebSocketException(StarletteWebSocketException):
+    """
+    A WebSocket exception you can raise in your own code to show errors to the client.
+
+    This is for client errors, invalid authentication, invalid data, etc. Not for server
+    errors in your code.
+
+    Read more about it in the
+    [FastAPI docs for WebSockets](https://fastapi.tiangolo.com/advanced/websockets/).
+
+    ## Example
+
+    ```python
+    from typing import Annotated
+
+    from fastapi import (
+        Cookie,
+        FastAPI,
+        WebSocket,
+        WebSocketException,
+        status,
+    )
+
+    app = FastAPI()
+
+    @app.websocket("/items/{item_id}/ws")
+    async def websocket_endpoint(
+        *,
+        websocket: WebSocket,
+        session: Annotated[str | None, Cookie()] = None,
+        item_id: str,
+    ):
+        if session is None:
+            raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
+        await websocket.accept()
+        while True:
+            data = await websocket.receive_text()
+            await websocket.send_text(f"Session cookie is: {session}")
+            await websocket.send_text(f"Message text was: {data}, for item ID: {item_id}")
+    ```
+    """
+
+    def __init__(
+        self,
+        code: Annotated[
+            int,
+            Doc(
+                """
+                A closing code from the
+                [valid codes defined in the specification](https://datatracker.ietf.org/doc/html/rfc6455#section-7.4.1).
+                """
+            ),
+        ],
+        reason: Annotated[
+            Union[str, None],
+            Doc(
+                """
+                The reason to close the WebSocket connection.
+
+                It is UTF-8-encoded data. The interpretation of the reason is up to the
+                application, it is not specified by the WebSocket specification.
+
+                It could contain text that could be human-readable or interpretable
+                by the client code, etc.
+                """
+            ),
+        ] = None,
+    ) -> None:
+        super().__init__(code=code, reason=reason)
+
+
 RequestErrorModel: Type[BaseModel] = create_model("Request")
 WebSocketErrorModel: Type[BaseModel] = create_model("WebSocket")