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 <harsha2k4@gmail.com>

* enable indexing of BlueprintGroup object

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* rename blueprint group file to fix spelling error

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* add documentation and additional unit tests

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* cleanup and optimize headers in unit test file

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* fix Bluprint Group iteratable method

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* add additional unit test to check StopIteration condition

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* cleanup iter protocol implemenation for blueprint group and add slots

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

* fix blueprint group middleware invocation identification

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

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

Signed-off-by: Harsha Narayana <harsha2k4@gmail.com>

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