Implement dict-like API on request objects for custom data. (#1666)

* Implement dict-like API on request objects for custom data.
* Updated docs about custom_context.

docs/sanic/middleware.md

@@ -39,8 +39,8 @@ app = Sanic(__name__)
 
 @app.middleware('request')
 async def add_key(request):
-    # Add a key to request object like dict object
-    request['foo'] = 'bar'
+    # Arbitrary data may be stored in request context:
+    request.ctx.foo = 'bar'
 
 
 @app.middleware('response')
@@ -53,16 +53,21 @@ async def prevent_xss(request, response):
 	response.headers["x-xss-protection"] = "1; mode=block"
 
 
+@app.get("/")
+async def index(request):
+    return sanic.response.text(request.ctx.foo)
+
+
 app.run(host="0.0.0.0", port=8000)
 ```
 
-The above code will apply the three middleware in order. The first middleware
-**add_key** will add a new key `foo` into `request` object. This worked because
-`request` object can be manipulated like `dict` object. Then, the second middleware
-**custom_banner** will change the HTTP response header *Server* to
-*Fake-Server*, and the last middleware **prevent_xss** will add the HTTP
-header for preventing Cross-Site-Scripting (XSS) attacks. These two functions
-are invoked *after* a user function returns a response.
+The three middlewares are executed in order:
+
+1. The first request middleware **add_key** adds a new key `foo` into request context.
+2. Request is routed to handler **index**, which gets the key from context and returns a text response.
+3. The first response middleware **custom_banner** changes the HTTP response header *Server* to
+say *Fake-Server*
+4. The second response middleware **prevent_xss** adds the HTTP header for preventing Cross-Site-Scripting (XSS) attacks.
 
 ## Responding early
 
@@ -81,6 +86,16 @@ async def halt_response(request, response):
 	return text('I halted the response')
 ```
 
+## Custom context
+
+Arbitrary data may be stored in `request.ctx`. A typical use case
+would be to store the user object acquired from database in an authentication
+middleware. Keys added are accessible to all later middleware as well as
+the handler over the duration of the request.
+
+Custom context is reserved for applications and extensions. Sanic itself makes
+no use of it.
+
 ## Listeners
 
 If you want to execute startup/teardown code as your server starts or closes, you can use the following listeners:

sanic/request.py

@@ -4,6 +4,7 @@ import warnings
 
 from collections import defaultdict, namedtuple
 from http.cookies import SimpleCookie
+from types import SimpleNamespace
 from urllib.parse import parse_qs, parse_qsl, unquote, urlunparse
 
 from httptools import parse_url  # type: ignore
@@ -62,7 +63,7 @@ class StreamBuffer:
         return self._queue.full()
 
 
-class Request(dict):
+class Request:
     """Properties of an HTTP request such as URL, headers, etc."""
 
     __slots__ = (
@@ -75,6 +76,7 @@ class Request(dict):
         "_socket",
         "app",
         "body",
+        "ctx",
         "endpoint",
         "headers",
         "method",
@@ -104,6 +106,7 @@ class Request(dict):
 
         # Init but do not inhale
         self.body_init()
+        self.ctx = SimpleNamespace()
         self.parsed_forwarded = None
         self.parsed_json = None
         self.parsed_form = None
@@ -120,10 +123,30 @@ class Request(dict):
             self.__class__.__name__, self.method, self.path
         )
 
-    def __bool__(self):
-        if self.transport:
-            return True
-        return False
+    def get(self, key, default=None):
+        """.. deprecated:: 19.9
+           Custom context is now stored in `request.custom_context.yourkey`"""
+        return self.ctx.__dict__.get(key, default)
+
+    def __contains__(self, key):
+        """.. deprecated:: 19.9
+           Custom context is now stored in `request.custom_context.yourkey`"""
+        return key in self.ctx.__dict__
+
+    def __getitem__(self, key):
+        """.. deprecated:: 19.9
+           Custom context is now stored in `request.custom_context.yourkey`"""
+        return self.ctx.__dict__[key]
+
+    def __delitem__(self, key):
+        """.. deprecated:: 19.9
+           Custom context is now stored in `request.custom_context.yourkey`"""
+        del self.ctx.__dict__[key]
+
+    def __setitem__(self, key, value):
+        """.. deprecated:: 19.9
+           Custom context is now stored in `request.custom_context.yourkey`"""
+        setattr(self.ctx, key, value)
 
     def body_init(self):
         self.body = []

tests/test_request_data.py

@@ -8,22 +8,72 @@ try:
 except ImportError:
     from json import loads
 
-
-def test_storage(app):
+def test_custom_context(app):
     @app.middleware("request")
     def store(request):
+        request.ctx.user = "sanic"
+        request.ctx.session = None
+
+    @app.route("/")
+    def handler(request):
+        # Accessing non-existant key should fail with AttributeError
+        try:
+            invalid = request.ctx.missing
+        except AttributeError as e:
+            invalid = str(e)
+        return json({
+            "user": request.ctx.user,
+            "session": request.ctx.session,
+            "has_user": hasattr(request.ctx, "user"),
+            "has_session": hasattr(request.ctx, "session"),
+            "has_missing": hasattr(request.ctx, "missing"),
+            "invalid": invalid
+        })
+
+    request, response = app.test_client.get("/")
+    assert response.json == {
+        "user": "sanic",
+        "session": None,
+        "has_user": True,
+        "has_session": True,
+        "has_missing": False,
+        "invalid": "'types.SimpleNamespace' object has no attribute 'missing'",
+    }
+
+
+# Remove this once the deprecated API is abolished.
+def test_custom_context_old(app):
+    @app.middleware("request")
+    def store(request):
+        try:
+            request["foo"]
+        except KeyError:
+            pass
         request["user"] = "sanic"
-        request["sidekick"] = "tails"
+        sidekick = request.get("sidekick", "tails")  # Item missing -> default
+        request["sidekick"] = sidekick
+        request["bar"] = request["sidekick"]
         del request["sidekick"]
 
     @app.route("/")
     def handler(request):
         return json(
-            {"user": request.get("user"), "sidekick": request.get("sidekick")}
+            {
+                "user": request.get("user"),
+                "sidekick": request.get("sidekick"),
+                "has_bar": "bar" in request,
+                "has_sidekick": "sidekick" in request,
+            }
         )
 
     request, response = app.test_client.get("/")
 
+    assert response.json == {
+        "user": "sanic",
+        "sidekick": None,
+        "has_bar": True,
+        "has_sidekick": False,
+    }
     response_json = loads(response.text)
     assert response_json["user"] == "sanic"
     assert response_json.get("sidekick") is None

tests/test_requests.py

@@ -1499,9 +1499,6 @@ def test_request_bool(app):
     request, response = app.test_client.get("/")
     assert bool(request)
 
-    request.transport = False
-    assert not bool(request)
-
 
 def test_request_parsing_form_failed(app, caplog):
     @app.route("/", methods=["POST"])