Enable Middleware Support for Blueprint Groups (#1399)

* enable blueprint group middleware support

This commit will enable the users to implement a middleware at the
blueprint group level whereby enforcing the middleware automatically to
each of the available Blueprints that are part of the group.

This will eanble a simple way in which a certain set of common features
and criteria can be enforced on a Blueprint group. i.e. authentication
and authorization

This commit will address the feature request raised as part of Issue #1386

Signed-off-by: Harsha Narayana <[email protected]>

* enable indexing of BlueprintGroup object

Signed-off-by: Harsha Narayana <[email protected]>

* rename blueprint group file to fix spelling error

Signed-off-by: Harsha Narayana <[email protected]>

* add documentation and additional unit tests

Signed-off-by: Harsha Narayana <[email protected]>

* cleanup and optimize headers in unit test file

Signed-off-by: Harsha Narayana <[email protected]>

* fix Bluprint Group iteratable method

Signed-off-by: Harsha Narayana <[email protected]>

* add additional unit test to check StopIteration condition

Signed-off-by: Harsha Narayana <[email protected]>

* cleanup iter protocol implemenation for blueprint group and add slots

Signed-off-by: Harsha Narayana <[email protected]>

* fix blueprint group middleware invocation identification

Signed-off-by: Harsha Narayana <[email protected]>

* feat: enable list behavior on blueprint group object and use append instead of properly to add blueprint to group

Signed-off-by: Harsha Narayana <[email protected]>

docs/sanic/api_reference.rst

@@ -20,6 +20,15 @@ sanic.blueprints module
     :undoc-members:
     :show-inheritance:
 
+sanic.blueprint_group module
+----------------------------
+
+.. automodule:: sanic.blueprint_group
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+
 sanic.config module
 -------------------
 

docs/sanic/blueprints.md

@@ -127,7 +127,7 @@ Blueprints have almost the same functionality as an application instance.
 WebSocket handlers can be registered on a blueprint using the `@bp.websocket`
 decorator or `bp.add_websocket_route` method.
 
-### Middleware
+### Blueprint Middleware
 
 Using blueprints allows you to also register middleware globally.
 
@@ -145,6 +145,36 @@ async def halt_response(request, response):
 	return text('I halted the response')
 ```
 
+### Blueprint Group Middleware
+Using this middleware will ensure that you can apply a common middleware to all the blueprints that form the
+current blueprint group under consideration.
+
+```python
+bp1 = Blueprint('bp1', url_prefix='/bp1')
+bp2 = Blueprint('bp2', url_prefix='/bp2')
+
+@bp1.middleware('request')
+async def bp1_only_middleware(request):
+    print('applied on Blueprint : bp1 Only')
+
+@bp1.route('/')
+async def bp1_route(request):
+    return text('bp1')
+
+@bp2.route('/<param>')
+async def bp2_route(request, param):
+    return text(param)
+
+group = Blueprint.group(bp1, bp2)
+
+@group.middleware('request')
+async def group_middleware(request):
+    print('common middleware applied for both bp1 and bp2')
+
+# Register Blueprint group under the app
+app.blueprint(group)
+```
+
 ### Exceptions
 
 Exceptions can be applied exclusively to blueprints globally.

sanic/app.py

@@ -15,6 +15,7 @@
 from urllib.parse import urlencode, urlunparse
 
 from sanic import reloader_helpers
+from sanic.blueprint_group import BlueprintGroup
 from sanic.config import BASE_LOGO, Config
 from sanic.constants import HTTP_METHODS
 from sanic.exceptions import SanicException, ServerError, URLBuildError
@@ -597,9 +598,11 @@ def register_middleware(self, middleware, attach_to="request"):
         :return: decorated method
         """
         if attach_to == "request":
-            self.request_middleware.append(middleware)
+            if middleware not in self.request_middleware:
+                self.request_middleware.append(middleware)
         if attach_to == "response":
-            self.response_middleware.appendleft(middleware)
+            if middleware not in self.response_middleware:
+                self.response_middleware.appendleft(middleware)
         return middleware
 
     # Decorator
@@ -681,7 +684,7 @@ def blueprint(self, blueprint, **options):
         :param options: option dictionary with blueprint defaults
         :return: Nothing
         """
-        if isinstance(blueprint, (list, tuple)):
+        if isinstance(blueprint, (list, tuple, BlueprintGroup)):
             for item in blueprint:
                 self.blueprint(item, **options)
             return

sanic/blueprint_group.py

@@ -0,0 +1,120 @@
+from collections import MutableSequence
+
+
+class BlueprintGroup(MutableSequence):
+    """
+    This class provides a mechanism to implement a Blueprint Group
+    using the `Blueprint.group` method. To avoid having to re-write
+    some of the existing implementation, this class provides a custom
+    iterator implementation that will let you use the object of this
+    class as a list/tuple inside the existing implementation.
+    """
+
+    __slots__ = ("_blueprints", "_url_prefix")
+
+    def __init__(self, url_prefix=None):
+        """
+        Create a new Blueprint Group
+
+        :param url_prefix: URL: to be prefixed before all the Blueprint Prefix
+        """
+        self._blueprints = []
+        self._url_prefix = url_prefix
+
+    @property
+    def url_prefix(self):
+        """
+        Retrieve the URL prefix being used for the Current Blueprint Group
+        :return: string with url prefix
+        """
+        return self._url_prefix
+
+    @property
+    def blueprints(self):
+        """
+        Retrieve a list of all the available blueprints under this group.
+        :return: List of Blueprint instance
+        """
+        return self._blueprints
+
+    def __iter__(self):
+        """Tun the class Blueprint Group into an Iterable item"""
+        return iter(self._blueprints)
+
+    def __getitem__(self, item):
+        """
+        This method returns a blueprint inside the group specified by
+        an index value. This will enable indexing, splice and slicing
+        of the blueprint group like we can do with regular list/tuple.
+
+        This method is provided to ensure backward compatibility with
+        any of the pre-existing usage that might break.
+
+        :param item: Index of the Blueprint item in the group
+        :return: Blueprint object
+        """
+        return self._blueprints[item]
+
+    def __setitem__(self, index: int, item: object) -> None:
+        """
+        Abstract method implemented to turn the `BlueprintGroup` class
+        into a list like object to support all the existing behavior.
+
+        This method is used to perform the list's indexed setter operation.
+
+        :param index: Index to use for inserting a new Blueprint item
+        :param item: New `Blueprint` object.
+        :return: None
+        """
+        self._blueprints[index] = item
+
+    def __delitem__(self, index: int) -> None:
+        """
+        Abstract method implemented to turn the `BlueprintGroup` class
+        into a list like object to support all the existing behavior.
+
+        This method is used to delete an item from the list of blueprint
+        groups like it can be done on a regular list with index.
+
+        :param index: Index to use for removing a new Blueprint item
+        :return: None
+        """
+        del self._blueprints[index]
+
+    def __len__(self) -> int:
+        """
+        Get the Length of the blueprint group object.
+        :return: Length of Blueprint group object
+        """
+        return len(self._blueprints)
+
+    def insert(self, index: int, item: object) -> None:
+        """
+        The Abstract class `MutableSequence` leverages this insert method to
+        perform the `BlueprintGroup.append` operation.
+
+        :param index: Index to use for removing a new Blueprint item
+        :param item: New `Blueprint` object.
+        :return: None
+        """
+        self._blueprints.insert(index, item)
+
+    def middleware(self, *args, **kwargs):
+        """
+        A decorator that can be used to implement a Middleware plugin to
+        all of the Blueprints that belongs to this specific Blueprint Group.
+
+        In case of nested Blueprint Groups, the same middleware is applied
+        across each of the Blueprints recursively.
+
+        :param args: Optional positional Parameters to be use middleware
+        :param kwargs: Optional Keyword arg to use with Middleware
+        :return: Partial function to apply the middleware
+        """
+        kwargs["bp_group"] = True
+
+        def register_middleware_for_blueprints(fn):
+            for blueprint in self.blueprints:
+                blueprint.middleware(fn, *args, **kwargs)
+
+        return register_middleware_for_blueprints

sanic/blueprints.py

@@ -1,5 +1,6 @@
 from collections import defaultdict, namedtuple
 
+from sanic.blueprint_group import BlueprintGroup
 from sanic.constants import HTTP_METHODS
 from sanic.views import CompositionView
 
@@ -78,10 +79,12 @@ def chain(nested):
             for i in nested:
                 if isinstance(i, (list, tuple)):
                     yield from chain(i)
+                elif isinstance(i, BlueprintGroup):
+                    yield from i.blueprints
                 else:
                     yield i
 
-        bps = []
+        bps = BlueprintGroup(url_prefix=url_prefix)
         for bp in chain(blueprints):
             if bp.url_prefix is None:
                 bp.url_prefix = ""
@@ -327,7 +330,13 @@ def register_middleware(_middleware):
             args = []
             return register_middleware(middleware)
         else:
-            return register_middleware
+            if kwargs.get("bp_group") and callable(args[0]):
+                middleware = args[0]
+                args = args[1:]
+                kwargs.pop("bp_group")
+                return register_middleware(middleware)
+            else:
+                return register_middleware
 
     def exception(self, *args, **kwargs):
         """