feat: support for soft deletion of casbin rules (#72)

* feat: add support for soft deletion of casbin rules

* refactor: improve reusability of test case

* fix: type hints

* test: soft delete

* chore: updated .gitignore

* refactor: pass the sqlalchemy attribute itself instead of the attribute name string

* test: softdelete flag in database

* refactor: save_policy
          - load rules from db before making changes
          - improved comments

* test: save_policy softdelete strategy

* fix: formatted code with black

* fix: do not create test.db by default

* fix: units tests for CI/CD pipeline

* docs: added Soft Delete example

* fix: make sure softdelete filter is applied

* docs: make usage of  explicit

* docs: moved softdelete logic into base class

* docs: improvement

* feat: validate the type of db_class_softdelete_attribute

* fix: default value of is_deleted flag

.gitignore

@@ -102,4 +102,7 @@ venv.bak/
 
 # mypy
 .mypy_cache/
-.idea
+.idea
+
+# vscode settings
+.vscode

README.md

@@ -49,6 +49,24 @@ else:
     pass
 ```
 
+## Soft Delete example
+
+Soft Delete for casbin rules is supported, only when using a custom casbin rule model.
+The Soft Delete mechanism is enabled by passing the attribute of the flag indicating whether
+a rule is deleted to `db_class_softdelete_attribute`.
+That attribute needs to be of type `sqlalchemy.Boolean`.
+
+```python
+adapter = Adapter(
+    engine,
+    db_class=MyCustomCasbinRuleModel,
+    db_class_softdelete_attribute=MyCustomCasbinRuleModel.is_deleted,
+)
+```
+
+Please be aware that this adapter only sets a flag like `is_deleted` to `True`.
+The provided model needs to handle the update of fields like `deleted_by`, `deleted_at`, etc.
+An example for this is given in [examples/softdelete.py](examples/softdelete.py).
 
 ### Getting Help
 

casbin_sqlalchemy_adapter/adapter.py

@@ -2,8 +2,8 @@
 
 import sqlalchemy
 from casbin import persist
-from sqlalchemy import Column, Integer, String
-from sqlalchemy import create_engine, or_
+from sqlalchemy import Column, Integer, String, Boolean
+from sqlalchemy import create_engine, or_, not_
 from sqlalchemy.orm import sessionmaker
 
 # declarative base class
@@ -56,15 +56,33 @@ class Filter:
 class Adapter(persist.Adapter, persist.adapters.UpdateAdapter):
     """the interface for Casbin adapters."""
 
-    def __init__(self, engine, db_class=None, filtered=False, create_all_models=True):
+    def __init__(
+        self,
+        engine,
+        db_class=None,
+        db_class_softdelete_attribute=None,
+        filtered=False,
+        create_all_models=True,
+    ):
         if isinstance(engine, str):
             self._engine = create_engine(engine)
         else:
             self._engine = engine
 
+        self.softdelete_attribute = None
+
         if db_class is None:
             db_class = CasbinRule
         else:
+            if db_class_softdelete_attribute is not None and not isinstance(
+                db_class_softdelete_attribute.type, Boolean
+            ):
+                msg = f"The type of db_class_softdelete_attribute needs to be {str(Boolean)!r}. "
+                msg += f"An attribute of type {str(type(db_class_softdelete_attribute.type))!r} was given."
+                raise ValueError(msg)
+            # Softdelete is only supported when using custom class
+            self.softdelete_attribute = db_class_softdelete_attribute
+
             for attr in (
                 "id",
                 "ptype",
@@ -102,7 +120,9 @@ def _session_scope(self):
     def load_policy(self, model):
         """loads all policy rules from the storage."""
         with self._session_scope() as session:
-            lines = session.query(self._db_class).all()
+            query = session.query(self._db_class)
+            query = self._softdelete_query(query)
+            lines = query.all()
             for line in lines:
                 persist.load_policy_line(str(line), model)
 
@@ -113,6 +133,7 @@ def load_filtered_policy(self, model, filter) -> None:
         """loads all policy rules from the storage."""
         with self._session_scope() as session:
             query = session.query(self._db_class)
+            query = self._softdelete_query(query)
             filters = self.filter_query(query, filter)
             filters = filters.all()
 
@@ -140,15 +161,60 @@ def _save_policy_line(self, ptype, rule, session=None):
 
     def save_policy(self, model):
         """saves all policy rules to the storage."""
+
+        # Use the default strategy when soft delete is not enabled
+        if self.softdelete_attribute is None:
+            with self._session_scope() as session:
+                query = session.query(self._db_class)
+                query.delete()
+                for sec in ["p", "g"]:
+                    if sec not in model.model.keys():
+                        continue
+                    for ptype, ast in model.model[sec].items():
+                        for rule in ast.policy:
+                            self._save_policy_line(ptype, rule, session=session)
+            return True
+
+        # Custom stategy for softdelete since it does not make sense to recreate all of the
+        # entries when using soft delete
         with self._session_scope() as session:
             query = session.query(self._db_class)
-            query.delete()
+            query = self._softdelete_query(query)
+
+            # Delete entries that are not part of the model anymore
+            lines_before_changes = query.all()
+
+            # Create new entries in the database
             for sec in ["p", "g"]:
                 if sec not in model.model.keys():
                     continue
                 for ptype, ast in model.model[sec].items():
                     for rule in ast.policy:
-                        self._save_policy_line(ptype, rule, session=session)
+                        # Filter for rule in the database
+                        filter_query = query.filter(self._db_class.ptype == ptype)
+                        for index, value in enumerate(rule):
+                            v_value = getattr(self._db_class, "v{}".format(index))
+                            filter_query = filter_query.filter(v_value == value)
+                        # If the rule is not present, create an entry in the database
+                        if filter_query.count() == 0:
+                            self._save_policy_line(ptype, rule, session=session)
+
+            for line in lines_before_changes:
+                ptype = line.ptype
+                sec = ptype[0]  # derived from persist.load_policy_line function
+                fields_with_None = [
+                    line.v0,
+                    line.v1,
+                    line.v2,
+                    line.v3,
+                    line.v4,
+                    line.v5,
+                ]
+                rule = [element for element in fields_with_None if element is not None]
+                # If the the rule is not part of the model, set the deletion flag to True
+                if not model.has_policy(sec, ptype, rule):
+                    setattr(line, self.softdelete_attribute.name, True)
+
         return True
 
     def add_policy(self, sec, ptype, rule):
@@ -164,10 +230,15 @@ def remove_policy(self, sec, ptype, rule):
         """removes a policy rule from the storage."""
         with self._session_scope() as session:
             query = session.query(self._db_class)
+            query = self._softdelete_query(query)
             query = query.filter(self._db_class.ptype == ptype)
             for i, v in enumerate(rule):
                 query = query.filter(getattr(self._db_class, "v{}".format(i)) == v)
-            r = query.delete()
+
+            if self.softdelete_attribute is None:
+                r = query.delete()
+            else:
+                r = query.update({self.softdelete_attribute: True})
 
         return True if r > 0 else False
 
@@ -177,20 +248,27 @@ def remove_policies(self, sec, ptype, rules):
             return
         with self._session_scope() as session:
             query = session.query(self._db_class)
+            query = self._softdelete_query(query)
             query = query.filter(self._db_class.ptype == ptype)
             rules = zip(*rules)
             for i, rule in enumerate(rules):
                 query = query.filter(
                     or_(getattr(self._db_class, "v{}".format(i)) == v for v in rule)
                 )
-            query.delete()
+
+            if self.softdelete_attribute is None:
+                query.delete()
+            else:
+                query.update({self.softdelete_attribute: True})
 
     def remove_filtered_policy(self, sec, ptype, field_index, *field_values):
         """removes policy rules that match the filter from the storage.
         This is part of the Auto-Save feature.
         """
         with self._session_scope() as session:
-            query = session.query(self._db_class).filter(self._db_class.ptype == ptype)
+            query = session.query(self._db_class)
+            query = self._softdelete_query(query)
+            query = query.filter(self._db_class.ptype == ptype)
 
             if not (0 <= field_index <= 5):
                 return False
@@ -200,12 +278,16 @@ def remove_filtered_policy(self, sec, ptype, field_index, *field_values):
                 if v != "":
                     v_value = getattr(self._db_class, "v{}".format(field_index + i))
                     query = query.filter(v_value == v)
-            r = query.delete()
+
+            if self.softdelete_attribute is None:
+                r = query.delete()
+            else:
+                r = query.update({self.softdelete_attribute: True})
 
         return True if r > 0 else False
 
     def update_policy(
-        self, sec: str, ptype: str, old_rule: [str], new_rule: [str]
+        self, sec: str, ptype: str, old_rule: list[str], new_rule: list[str]
     ) -> None:
         """
         Update the old_rule with the new_rule in the database (storage).
@@ -219,7 +301,9 @@ def update_policy(
         """
 
         with self._session_scope() as session:
-            query = session.query(self._db_class).filter(self._db_class.ptype == ptype)
+            query = session.query(self._db_class)
+            query = self._softdelete_query(query)
+            query = query.filter(self._db_class.ptype == ptype)
 
             # locate the old rule
             for index, value in enumerate(old_rule):
@@ -241,12 +325,8 @@ def update_policies(
         self,
         sec: str,
         ptype: str,
-        old_rules: [
-            [str],
-        ],
-        new_rules: [
-            [str],
-        ],
+        old_rules: list[list[str]],
+        new_rules: list[list[str]],
     ) -> None:
         """
         Update the old_rules with the new_rules in the database (storage).
@@ -262,8 +342,8 @@ def update_policies(
             self.update_policy(sec, ptype, old_rules[i], new_rules[i])
 
     def update_filtered_policies(
-        self, sec, ptype, new_rules: [[str]], field_index, *field_values
-    ) -> [[str]]:
+        self, sec, ptype, new_rules: list[list[str]], field_index, *field_values
+    ) -> list[list[str]]:
         """update_filtered_policies updates all the policies on the basis of the filter."""
 
         filter = Filter()
@@ -278,16 +358,15 @@ def update_filtered_policies(
 
         self._update_filtered_policies(new_rules, filter)
 
-    def _update_filtered_policies(self, new_rules, filter) -> [[str]]:
+    def _update_filtered_policies(self, new_rules, filter) -> list[list[str]]:
         """_update_filtered_policies updates all the policies on the basis of the filter."""
 
         with self._session_scope() as session:
-
             # Load old policies
 
-            query = session.query(self._db_class).filter(
-                self._db_class.ptype == filter.ptype
-            )
+            query = session.query(self._db_class)
+            query = self._softdelete_query(query)
+            query = query.filter(self._db_class.ptype == filter.ptype)
             filtered_query = self.filter_query(query, filter)
             old_rules = filtered_query.all()
 
@@ -302,3 +381,9 @@ def _update_filtered_policies(self, new_rules, filter) -> [[str]]:
             # return deleted rules
 
             return old_rules
+
+    def _softdelete_query(self, query):
+        query_softdelete = query
+        if self.softdelete_attribute is not None:
+            query_softdelete = query_softdelete.where(not_(self.softdelete_attribute))
+        return query_softdelete

examples/softdelete.py

@@ -0,0 +1,91 @@
+from datetime import datetime, UTC
+
+import casbin
+from casbin_sqlalchemy_adapter import Base, Adapter
+from sqlalchemy import false, Column, DateTime, String, Integer, Boolean
+from sqlalchemy.engine.default import DefaultExecutionContext
+
+from some_user_library import get_current_user_id
+
+
+def _deleted_at_default(context: DefaultExecutionContext) -> datetime | None:
+    current_parameters = context.get_current_parameters()
+    if current_parameters.get("is_deleted"):
+        return datetime.now(UTC)
+    else:
+        return None
+
+
+def _deleted_by_default(context: DefaultExecutionContext) -> int | None:
+    current_parameters = context.get_current_parameters()
+    if current_parameters.get("is_deleted"):
+        return get_current_user_id()
+    else:
+        return None
+
+
+class BaseModel(Base):
+    __abstract__ = True
+
+    created_at = Column(DateTime, default=lambda: datetime.now(UTC), nullable=False)
+    updated_at = Column(
+        DateTime,
+        default=lambda: datetime.now(UTC),
+        onupdate=lambda: datetime.now(UTC),
+        nullable=False,
+    )
+    deleted_at = Column(
+        DateTime,
+        default=_deleted_at_default,
+        onupdate=_deleted_at_default,
+        nullable=True,
+    )
+
+    created_by = Column(Integer, default=get_current_user_id, nullable=False)
+    updated_by = Column(
+        Integer,
+        default=get_current_user_id,
+        onupdate=get_current_user_id,
+        nullable=False,
+    )
+    deleted_by = Column(
+        Integer,
+        default=_deleted_by_default,
+        onupdate=_deleted_by_default,
+        nullable=True,
+    )
+    is_deleted = Column(
+        Boolean,
+        default=False,
+        server_default=false(),
+        index=True,
+        nullable=False,
+    )
+
+
+class CasbinSoftDeleteRule(BaseModel):
+    __tablename__ = "casbin_rule"
+
+    id = Column(Integer, primary_key=True)
+    ptype = Column(String(255))
+    v0 = Column(String(255))
+    v1 = Column(String(255))
+    v2 = Column(String(255))
+    v3 = Column(String(255))
+    v4 = Column(String(255))
+    v5 = Column(String(255))
+
+
+engine = your_engine_factory()
+# Initialize the Adapter, pass your custom CasbinRule model
+# and pass the Boolean field indicating whether a rule is deleted or not
+# your model needs to handle the update of fields
+# 'updated_by', 'updated_at', 'deleted_by', etc.
+adapter = Adapter(
+    engine,
+    CasbinSoftDeleteRule,
+    CasbinSoftDeleteRule.is_deleted,
+)
+# Create the Enforcer, etc.
+e = casbin.Enforcer("path/to/model.conf", adapter)
+...