Disjoin patterns without dependencies from prior partial matches. #224

When a query/pattern does not depend on preceding matches, it should be separated into an independent sub-network, such that it's only evaluated based on it's inputs chaning, and not based on the preceding partial matches.
The corolary to this is that a binding expression that does not depend on any preceding matches will only evaluate once (hence fixing the BindingEvaluationExceptionTest to introduce the dependency on the preceding fact match).

src/NRules/NRules/Rete/ReteBuilder.cs

@@ -125,10 +125,10 @@ protected override void VisitPattern(ReteBuilderContext context, PatternElement
             }
             else
             {
-                if (conditions.Any())
+                var isJoined = element.Imports.Any();
+                if (isJoined)
                 {
-                    var isJoined = element.Imports.Any();
-                    if (isJoined)
+                    if (conditions.Any())
                     {
                         BuildSubnet(context, element);
 
@@ -137,20 +137,23 @@ protected override void VisitPattern(ReteBuilderContext context, PatternElement
                     }
                     else
                     {
-                        var joinContext = new ReteBuilderContext(context.Rule, _dummyNode);
-                        BuildSubnet(joinContext, element);
-
-                        joinContext.RegisterDeclaration(element.Declaration);
-                        BuildJoinNode(joinContext, element, conditions);
-                        BuildAdapter(joinContext);
-                        context.AlphaSource = joinContext.AlphaSource;
-
+                        Visit(context, element.Source);
                         context.RegisterDeclaration(element.Declaration);
                     }
                 }
                 else
                 {
-                    Visit(context, element.Source);
+                    var joinContext = new ReteBuilderContext(context.Rule, _dummyNode);
+                    BuildSubnet(joinContext, element);
+
+                    joinContext.RegisterDeclaration(element.Declaration);
+                    if (conditions.Any())
+                    {
+                        BuildJoinNode(joinContext, element, conditions);
+                        BuildAdapter(joinContext);
+                    }
+                    context.AlphaSource = joinContext.AlphaSource;
+
                     context.RegisterDeclaration(element.Declaration);
                 }
             }

src/NRules/Tests/NRules.IntegrationTests/BindingEvaluationExceptionTest.cs

@@ -146,8 +146,8 @@ protected override void SetUpRules()
             SetUpRule<TestRule>();
         }
 
-        private static readonly Func<string> SuccessfulBinding = () => "value";
-        private static readonly Func<string> ThrowBinding = () => throw new InvalidOperationException("Binding failed");
+        private static readonly Func<FactType, string> SuccessfulBinding = f => "value";
+        private static readonly Func<FactType, string> ThrowBinding = f => throw new InvalidOperationException("Binding failed");
 
         public class FactType
         {
@@ -156,16 +156,16 @@ public class FactType
 
         public class TestRule : Rule
         {
-            public Func<string> Binding = SuccessfulBinding;
+            public Func<FactType, string> Binding = SuccessfulBinding;
 
             public override void Define()
             {
                 FactType fact = null;
                 string binding = null;
 
                 When()
-                    .Match<FactType>(() => fact, f => f.TestProperty.StartsWith("Valid"))
-                    .Let(() => binding, () => Binding());
+                    .Match(() => fact, f => f.TestProperty.StartsWith("Valid"))
+                    .Let(() => binding, () => Binding(fact));
                 Then()
                     .Do(ctx => NoOp());
             }