feat: Fixed the subjectPriority sorting algorithm and support for c…

…hecking the subject role link loop (#322)

* fix: Fixed the `subjectPriority` sorting algorithm and support for checking the subject role link loop.

* fix: Run black

casbin/model/model.py

@@ -134,14 +134,20 @@ def compare_policy(policy):
                 name = self.get_name_with_domain(domain, policy[sub_index])
                 return subject_hierarchy_map.get(name, 0)
 
-            assertion.policy = sorted(assertion.policy, key=compare_policy, reverse=True)
+            assertion.policy = sorted(assertion.policy, key=compare_policy)
             for i, policy in enumerate(assertion.policy):
                 assertion.policy_map[",".join(policy)] = i
 
     def get_subject_hierarchy_map(self, policies):
-        subject_hierarchy_map = {}
-        # Tree structure of role
-        policy_map = {}
+        """
+        Get the subject hierarchy from the policy.
+        Select the lowest level subject in multiple rounds until all subjects are selected.
+        Return the subject hierarchy dictionary, the subject is the key, and the level is the value.
+        The level starts from 0 and increases in turn. The smaller the level, the higher the priority.
+        """
+        # Init unsorted policy, and subject
+        unsorted_policy = []
+        unsorted_sub = set()
         for policy in policies:
             if len(policy) < 2:
                 raise RuntimeError("policy g expect 2 more params")
@@ -150,33 +156,28 @@ def get_subject_hierarchy_map(self, policies):
                 domain = policy[2]
             child = self.get_name_with_domain(domain, policy[0])
             parent = self.get_name_with_domain(domain, policy[1])
-            if parent not in policy_map.keys():
-                policy_map[parent] = [child]
-            else:
-                policy_map[parent].append(child)
-            if child not in subject_hierarchy_map.keys():
-                subject_hierarchy_map[child] = 0
-            if parent not in subject_hierarchy_map.keys():
-                subject_hierarchy_map[parent] = 0
-            subject_hierarchy_map[child] = 1
-        # Use queues for levelOrder
-        queue = []
-        for k, v in subject_hierarchy_map.items():
-            root = k
-            if v != 0:
-                continue
-            lv = 0
-            queue.append(root)
-            while len(queue) != 0:
-                sz = len(queue)
-                for _ in range(sz):
-                    node = queue.pop(0)
-                    subject_hierarchy_map[node] = lv
-                    if node in policy_map.keys():
-                        for child in policy_map[node]:
-                            queue.append(child)
-                lv += 1
-        return subject_hierarchy_map
+            unsorted_policy.append([child, parent])
+            unsorted_sub.add(child)
+            unsorted_sub.add(parent)
+        # sort policy,and update sorted_sub_list
+        sorted_sub_list = []
+        while len(unsorted_policy) > 0:
+            # get all parent subject
+            parent_sub = {p[1] for p in unsorted_policy if p[1] != ""}
+            # remove parent subject from unsorted_sub
+            sorted_sub = unsorted_sub - parent_sub
+            if not sorted_sub:
+                raise RuntimeError("cycle dependency in subject hierarchy.subjects: {}".format(unsorted_sub))
+            # update sorted_sub_list
+            sorted_sub_list.append(sorted_sub)
+            # remove sorted subject, and update unsorted_policy
+            unsorted_policy = [p for p in unsorted_policy if p[0] not in sorted_sub]
+            # update unsorted_sub
+            unsorted_sub = unsorted_sub - sorted_sub
+        if len(unsorted_sub) > 0:
+            sorted_sub_list.append(unsorted_sub)
+        # Tree structure of subject
+        return {sub: i for i, subs in enumerate(sorted_sub_list) for sub in subs}
 
     def get_name_with_domain(self, domain, name):
         return "{}{}{}".format(domain, DEFAULT_SEPARATOR, name)

tests/model/test_model.py

@@ -0,0 +1,47 @@
+from unittest import TestCase
+
+from casbin import Model
+from casbin.model.model import DEFAULT_DOMAIN
+
+
+class TestModel(TestCase):
+    m = Model()
+
+    def check_hierarchy(self, policies: list, subject_hierarchy_map: dict):
+        """check_hierarchy checks the hierarchy of the subject hierarchy map"""
+        for policy in policies:
+            if len(policy) < 2:
+                raise RuntimeError("policy g expect 2 more params")
+            domain = DEFAULT_DOMAIN
+            if len(policy) != 2:
+                domain = policy[2]
+            child = self.m.get_name_with_domain(domain, policy[0])
+            parent = self.m.get_name_with_domain(domain, policy[1])
+            assert subject_hierarchy_map[child] < subject_hierarchy_map[parent]
+
+    def test_get_subject_hierarchy_map(self):
+        # test 1
+        policies = [
+            ["A1", "B1"],
+            ["A1", "B2"],
+            ["A2", "B3"],
+        ]
+        res = self.m.get_subject_hierarchy_map(policies)
+        self.check_hierarchy(policies, res)
+        # test 2
+        policies = [
+            ["A1", "B1"],
+            ["B1", "B2"],
+            ["B2", "B3"],
+            ["B1", "B4"],
+            ["A1", "B2"],
+        ]
+        res = self.m.get_subject_hierarchy_map(policies)
+        self.check_hierarchy(policies, res)
+        # test 3
+        policies = [
+            ["B1", "B2"],
+            ["B2", "B3"],
+            ["B3", "B1"],
+        ]
+        self.assertRaises(RuntimeError, self.m.get_subject_hierarchy_map, policies)