feat: Support eval with dynamic request value type (#360)

Signed-off-by: Taoyuesong <634774653@qq.com>

Author: Taoyuesong

Casbin.UnitTests/Fixtures/TestModelFixture.cs

@@ -95,6 +95,10 @@ public class TestModelFixture
     public static readonly string RbacWithIndexMatcherModelText = ReadTestFile("rbac_with_index_matcher_model.conf");
     public static readonly string RbacWithIndexMatcherPolicyText = ReadTestFile("rbac_with_index_matcher_policy.csv");
 
+    // https://github.com/casbin/Casbin.NET/issues/354
+    public static readonly string AbacWithDynamicValueTypeModelText = ReadTestFile("abac_with_dynamic_value_type_model.conf");
+    public static readonly string AbacWithDynamicValueTypePolicyText = ReadTestFile("abac_with_dynamic_value_type_policy.csv");
+
     public static IModel GetNewAbacModel() => GetNewTestModel(AbacModelText);
 
     public static IModel GetNewAbacWithEvalModel() => GetNewTestModel(AbacWithEvalModelText, AbacWithEvalPolicyText);

Casbin.UnitTests/ModelTests/ModelTest.cs

@@ -752,6 +752,25 @@ public void TestRbacWithIndexMatcher()
         Assert.True(e.Enforce(rule, "Admin", "/api/transactions/getTransactions", "POST"));
     }
 
+    [Fact]
+    public void TestAbacWithDynamicValueType()
+    {
+        Enforcer e = new(TestModelFixture.GetNewTestModel(
+            TestModelFixture.AbacWithDynamicValueTypeModelText,
+            TestModelFixture.AbacWithDynamicValueTypePolicyText));
+        var sub = new { Name = "bob" };
+        var obj1 = new { Object = "/data1", Property1 = "prop-1" };
+        var obj2 = new { Object = "/data2", Property2 = "prop-2" };
+        var obj3 = new { Object = "/data2", Property3 = "prop-3" };
+        Assert.True(e.Enforce(sub, obj1, "read"));
+        Assert.True(e.Enforce(sub, obj2, "read"));
+        Assert.False(e.Enforce(sub, obj3, "read"));
+        // Request again to test the cache hit logic.
+        Assert.True(e.Enforce(sub, obj1, "read"));
+        Assert.True(e.Enforce(sub, obj2, "read"));
+        Assert.False(e.Enforce(sub, obj3, "read"));
+    }
+
     public class TestResource
     {
         public TestResource(string name, string owner)

Casbin.UnitTests/examples/abac_with_dynamic_value_type_model.conf

@@ -0,0 +1,14 @@
+[request_definition]
+r = sub, obj, act
+
+[policy_definition]
+p = sub, obj, act, rule
+
+[policy_effect]
+e = some(where (p.eft == allow))
+
+[matchers]
+m = r.sub.Name == p.sub && \
+    r.obj.Object == p.obj && \
+    r.act == p.act && \
+    eval(p.rule)

Casbin.UnitTests/examples/abac_with_dynamic_value_type_policy.csv

@@ -0,0 +1,2 @@
+p, bob, /data1, read, r.obj.Property1 == "prop-1"
+p, bob, /data2, read, r.obj.Property2 == "prop-2"

Casbin/Evaluation/ExpressionHandler.cs

@@ -18,6 +18,8 @@ internal class ExpressionHandler : IExpressionHandler
     private Interpreter _interpreter;
 #endif
 
+    private bool TryCompile { get; set; } = true;
+
     public ExpressionHandler()
     {
         _interpreter = CreateInterpreter();
@@ -76,13 +78,23 @@ public bool Invoke<TRequest, TPolicy>(in EnforceContext context, string expressi
             return func(request, policy);
         }
 
-        if (_cachePool.TryGetFunc(expressionString,
-                out Func<TRequest, TPolicy, bool> genericFunc) is not false)
+        if (_cachePool.TryGetFunc(expressionString, out Func<TRequest, TPolicy, bool> genericFunc))
+        {
+            return genericFunc is not null && genericFunc(request, policy);
+        }
+
+        if (TryCompile is false)
         {
+            genericFunc = CompileExpression<TRequest, TPolicy>(in context, expressionString);
+            _cachePool.SetFunc(expressionString, genericFunc);
             return genericFunc(request, policy);
         }
 
-        genericFunc = CompileExpression<TRequest, TPolicy>(in context, expressionString);
+        if (TryCompileExpression(in context, expressionString, out genericFunc) is false)
+        {
+            _cachePool.SetFunc(expressionString, genericFunc);
+            return false;
+        }
         _cachePool.SetFunc(expressionString, genericFunc);
         return genericFunc(request, policy);
     }
@@ -96,6 +108,23 @@ private Func<TRequest, TPolicy, bool> CompileExpression<TRequest, TPolicy>(in En
             context.View.RequestType, context.View.PolicyType);
     }
 
+    private bool TryCompileExpression<TRequest, TPolicy>(in EnforceContext context,
+        string expressionString, out Func<TRequest, TPolicy, bool> func)
+        where TRequest : IRequestValues
+        where TPolicy : IPolicyValues
+    {
+        try
+        {
+            func = CompileExpression<TRequest, TPolicy>(in context, expressionString);
+        }
+        catch (Exception)
+        {
+            func = null;
+            return false;
+        }
+        return true;
+    }
+
     private Interpreter CreateInterpreter()
     {
         var interpreter = new Interpreter();