Log expression compilation errors and replace single quotes in expressions

Co-authored-by: hsluoyz <3787410+hsluoyz@users.noreply.github.com>

Author: Copilot

Casbin.UnitTests/Mock/MockLogger.cs

@@ -1,5 +1,6 @@
 #if !NET452
 using System;
+using System.Collections.Generic;
 using Microsoft.Extensions.Logging;
 using Xunit.Abstractions;
 
@@ -11,11 +12,14 @@ public class MockLogger<T> : ILogger<T>
 
         public MockLogger(ITestOutputHelper testOutputHelper) => _testOutputHelper = testOutputHelper;
 
+        public List<(LogLevel Level, Exception Exception, string Message)> Logs { get; } = new();
+
         public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception,
             Func<TState, Exception, string> formatter)
         {
             string outPut = formatter(state, null);
             _testOutputHelper.WriteLine(outPut);
+            Logs.Add((logLevel, exception, outPut));
         }
 
         public bool IsEnabled(LogLevel logLevel) => true;

Casbin.UnitTests/ModelTests/EnforcerTest.cs

@@ -1290,4 +1290,33 @@ public async Task TestEnforceExWithMatcherAsync()
     }
 
     #endregion
+
+#if !NET452
+    #region ExpressionHandler Tests
+
+    [Fact]
+    public void TestExpressionHandlerSingleQuoteReplacement()
+    {
+        Enforcer e = new(TestModelFixture.GetBasicTestModel());
+        // Single quotes should be replaced with double quotes to handle DynamicExpresso limitations
+        string matcherWithSingleQuotes = "r.sub == 'alice' && r.obj == p.obj && r.act == p.act";
+
+        Assert.True(e.EnforceWithMatcher(matcherWithSingleQuotes, "alice", "data1", "read"));
+        Assert.False(e.EnforceWithMatcher(matcherWithSingleQuotes, "alice", "data1", "write"));
+        Assert.False(e.EnforceWithMatcher(matcherWithSingleQuotes, "bob", "data1", "read"));
+    }
+
+    [Fact]
+    public void TestExpressionHandlerLogsWarningOnInvalidExpression()
+    {
+        var logger = new MockLogger<Enforcer>(_testOutputHelper);
+        Enforcer e = new(TestModelFixture.GetBasicTestModel()) { Logger = logger };
+
+        // An invalid expression should return false and log a warning
+        Assert.False(e.EnforceWithMatcher("this_is_not_valid!!!", "alice", "data1", "read"));
+        Assert.Contains(logger.Logs, log => log.Level == Microsoft.Extensions.Logging.LogLevel.Warning);
+    }
+
+    #endregion
+#endif
 }

Casbin/Enforcer.Internal.cs

@@ -72,6 +72,12 @@ private bool InternalEnforce<TRequest, TPolicy>(in EnforceContext context, in TR
     {
         EnforceSession session = new EnforceSession();
         IExpressionHandler expressionHandler = Model.ExpressionHandler;
+#if !NET452
+        if (expressionHandler is ExpressionHandler exprHandler)
+        {
+            exprHandler.Logger = Logger;
+        }
+#endif
         PolicyScanner<TRequest> scanner = context.View.PolicyAssertion.Scan(in requestValues);
 
         EffectChain effectChain = new();

Casbin/Evaluation/ExpressionHandler.cs

@@ -5,6 +5,9 @@
 using Casbin.Functions;
 using Casbin.Model;
 using DynamicExpresso;
+#if !NET452
+using Microsoft.Extensions.Logging;
+#endif
 
 namespace Casbin.Evaluation;
 
@@ -20,6 +23,10 @@ internal class ExpressionHandler : IExpressionHandler
 
     private bool TryCompile { get; set; } = true;
 
+#if !NET452
+    internal ILogger Logger { get; set; }
+#endif
+
     public ExpressionHandler()
     {
         _interpreter = CreateInterpreter();
@@ -65,6 +72,7 @@ public bool Invoke<TRequest, TPolicy>(in EnforceContext context, string expressi
         where TRequest : IRequestValues
         where TPolicy : IPolicyValues
     {
+        expressionString = expressionString.Replace('\'', '"');
         if (context.View.SupportGeneric is false)
         {
             if (_cachePool.TryGetFunc(expressionString,
@@ -117,9 +125,12 @@ private bool TryCompileExpression<TRequest, TPolicy>(in EnforceContext context,
         {
             func = CompileExpression<TRequest, TPolicy>(in context, expressionString);
         }
-        catch (Exception)
+        catch (Exception e)
         {
             func = null;
+#if !NET452
+            Logger?.LogWarning(e, "Failed to compile the expression \"{ExpressionString}\".", expressionString);
+#endif
             return false;
         }
         return true;