From bc7f4bd3d35b2b06272328e1e701edcf51d48cd2 Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Tue, 27 Aug 2019 09:41:04 +0100
Subject: [PATCH] Application state

---
 docs/applications.md           | 11 +++++++++++
 starlette/applications.py      |  3 ++-
 starlette/datastructures.py    | 26 ++++++++++++++++++++++++++
 starlette/middleware/errors.py |  2 +-
 starlette/requests.py          | 20 +-------------------
 5 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/docs/applications.md b/docs/applications.md
index 0092a3b4..e19928f5 100644
--- a/docs/applications.md
+++ b/docs/applications.md
@@ -76,3 +76,14 @@ exceptions that occur within the application:
 * `app.add_exception_handler(exc_class_or_status_code, handler)` - Add an error handler. The handler function may be either a coroutine or a regular function, with a signature like `func(request, exc) -> response`.
 * `@app.exception_handler(exc_class_or_status_code)` - Add an error handler, decorator style.
 * `app.debug` - Enable or disable error tracebacks in the browser.
+
+### Storing state on the app instance
+
+You can store arbitrary extra state on the application instance, using the
+generic `app.state` attribute.
+
+For example:
+
+```python
+app.state.ADMIN_EMAIL = 'admin@example.org'
+```
diff --git a/starlette/applications.py b/starlette/applications.py
index 8e7694bc..4b19fdc1 100644
--- a/starlette/applications.py
+++ b/starlette/applications.py
@@ -1,6 +1,6 @@
 import typing
 
-from starlette.datastructures import URLPath
+from starlette.datastructures import State, URLPath
 from starlette.exceptions import ExceptionMiddleware
 from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.middleware.errors import ServerErrorMiddleware
@@ -13,6 +13,7 @@ class Starlette:
         self, debug: bool = False, routes: typing.List[BaseRoute] = None
     ) -> None:
         self._debug = debug
+        self.state = State()
         self.router = Router(routes)
         self.exception_middleware = ExceptionMiddleware(self.router, debug=debug)
         self.error_middleware = ServerErrorMiddleware(
diff --git a/starlette/datastructures.py b/starlette/datastructures.py
index ae23e237..bc5ae36f 100644
--- a/starlette/datastructures.py
+++ b/starlette/datastructures.py
@@ -628,3 +628,29 @@ class MutableHeaders(Headers):
         if existing is not None:
             vary = ", ".join([existing, vary])
         self["vary"] = vary
+
+
+class State(object):
+    """
+    An object that can be used to store arbitrary state.
+
+    Used for `request.state` and `app.state`.
+    """
+
+    def __init__(self, state: typing.Dict = None):
+        if state is None:
+            state = {}
+        super(State, self).__setattr__("_state", state)
+
+    def __setattr__(self, key: typing.Any, value: typing.Any) -> None:
+        self._state[key] = value
+
+    def __getattr__(self, key: typing.Any) -> typing.Any:
+        try:
+            return self._state[key]
+        except KeyError:
+            message = "'{}' object has no attribute '{}'"
+            raise AttributeError(message.format(self.__class__.__name__, key))
+
+    def __delattr__(self, key: typing.Any) -> None:
+        del self._state[key]
diff --git a/starlette/middleware/errors.py b/starlette/middleware/errors.py
index a3fe4f35..d90bf275 100644
--- a/starlette/middleware/errors.py
+++ b/starlette/middleware/errors.py
@@ -1,5 +1,5 @@
-import html
 import asyncio
+import html
 import inspect
 import traceback
 import typing
diff --git a/starlette/requests.py b/starlette/requests.py
index be05f291..a71c9075 100644
--- a/starlette/requests.py
+++ b/starlette/requests.py
@@ -4,7 +4,7 @@ import json
 import typing
 from collections.abc import Mapping
 
-from starlette.datastructures import URL, Address, FormData, Headers, QueryParams
+from starlette.datastructures import URL, Address, FormData, Headers, QueryParams, State
 from starlette.formparsers import FormParser, MultiPartParser
 from starlette.types import Message, Receive, Scope
 
@@ -18,24 +18,6 @@ class ClientDisconnect(Exception):
     pass
 
 
-class State(object):
-    def __init__(self, state: typing.Dict = {}):
-        super(State, self).__setattr__("_state", state)
-
-    def __setattr__(self, key: typing.Any, value: typing.Any) -> None:
-        self._state[key] = value
-
-    def __getattr__(self, key: typing.Any) -> typing.Any:
-        try:
-            return self._state[key]
-        except KeyError:
-            message = "'{}' object has no attribute '{}'"
-            raise AttributeError(message.format(self.__class__.__name__, key))
-
-    def __delattr__(self, key: typing.Any) -> None:
-        del self._state[key]
-
-
 class HTTPConnection(Mapping):
     """
     A base class for incoming HTTP connections, that is used to provide