Use custom classproperty for python 3.8 compatibility

We can use @classmethod and @Property together in python 3.9. Not so in
3.8

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

vulnerabilities/helpers.py

@@ -167,3 +167,12 @@ def split_markdown_front_matter(text: str) -> Tuple[str, str]:
         return frontmatter, markdown
 
     return "", text
+
+
+# TODO: Replace this with combination of @classmethod and @property after upgrading to python 3.9
+class classproperty(object):
+    def __init__(self, fget):
+        self.fget = fget
+
+    def __get__(self, owner_self, owner_cls):
+        return self.fget(owner_cls)

vulnerabilities/importer.py

@@ -43,6 +43,7 @@
 from univers.version_range import VersionRange
 from univers.versions import Version
 from vulnerabilities.helpers import nearest_patched_package
+from vulnerabilities.helpers import classproperty
 from vulnerabilities.oval_parser import OvalParser
 from vulnerabilities.severity_systems import ScoringSystem
 from vulnerabilities.severity_systems import SCORING_SYSTEMS
@@ -218,9 +219,8 @@ class NoLicenseError(Exception):
 
 class Importer:
     """
-    An Importer collects data from various upstreams and returns corresponding
-    AdvisoryData objects in its advisory_data method.
-    Subclass this class to implement an importer
+    An Importer collects data from various upstreams and returns corresponding AdvisoryData objects
+    in its advisory_data method.  Subclass this class to implement an importer
     """
 
     spdx_license_expression = ""
@@ -229,14 +229,12 @@ def __init__(self):
         if not self.spdx_license_expression:
             raise Exception(f"Cannot run importer {self!r} without a license")
 
-    @classmethod
-    @property
-    def qualified_name(cls):
+    @classproperty
+    def qualified_name(self):
         """
-        Fully qualified name prefixed with the module name of the data source
-        used in logging.
+        Fully qualified name prefixed with the module name of the improver used in logging.
         """
-        return f"{cls.__module__}.{cls.__qualname__}"
+        return f"{self.__module__}.{self.__qualname__}"
 
     def advisory_data(self) -> Iterable[AdvisoryData]:
         """

vulnerabilities/improver.py

@@ -10,6 +10,7 @@
 
 from vulnerabilities.importer import Reference
 from vulnerabilities.importer import AdvisoryData
+from vulnerabilities.helpers import classproperty
 
 logger = logging.getLogger(__name__)
 
@@ -73,13 +74,19 @@ def from_advisory_data(cls, advisory_data, confidence, affected_purls, fixed_pur
 
 class Improver:
     """
-    Improvers are responsible to improve already imported data by an importer.
-    An improver is required to override the ``interesting_advisories`` property method to return a
-    QuerySet of ``Advisory`` objects. These advisories are then passed to ``get_inferences`` method
-    which is responsible for returning an iterable of ``Inferences`` for that particular
-    ``Advisory``
+    Improvers are responsible to improve already imported data by an importer.  An improver is
+    required to override the ``interesting_advisories`` property method to return a QuerySet of
+    ``Advisory`` objects. These advisories are then passed to ``get_inferences`` method which is
+    responsible for returning an iterable of ``Inferences`` for that particular ``Advisory``
     """
 
+    @classproperty
+    def qualified_name(self):
+        """
+        Fully qualified name prefixed with the module name of the improver used in logging.
+        """
+        return f"{self.__module__}.{self.__qualname__}"
+
     @property
     def interesting_advisories(self) -> QuerySet:
         """
@@ -92,12 +99,3 @@ def get_inferences(self, advisory_data: AdvisoryData) -> Iterable[Inference]:
         Generate and return Inferences for the given advisory data
         """
         raise NotImplementedError
-
-    @classmethod
-    @property
-    def qualified_name(cls):
-        """
-        Fully qualified name prefixed with the module name of the improver
-        used in logging.
-        """
-        return f"{cls.__module__}.{cls.__qualname__}"