fix: case-sensitive resolution of same-spelling variables (issue #434)

source/Handlebars.Test/Issues/Issue434Tests.cs

@@ -0,0 +1,22 @@
+using System.Dynamic;
+using Xunit;
+
+namespace HandlebarsDotNet.Test
+{
+    public class Issue434Tests
+    {
+        [Fact]
+        public void Issue434_CaseSensitiveLookupWithSameSpellingVariables()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("{{TEST}} {{test}}");
+            dynamic data = new ExpandoObject();
+            data.TEST = "Upper";
+            data.test = "Lower";
+            var result = template(data);
+            var parts = result.Split(' ');
+            Assert.Equal("Upper", parts[0]);
+            Assert.Equal("Lower", parts[1]);
+        }
+    }
+}

source/Handlebars/Compiler/Translation/Expression/PathBinder.cs

@@ -36,17 +36,27 @@
 
             if (pex.Context == PathExpression.ResolutionContext.Parameter) return resolvePath;
             if (pathInfo.IsVariable || pathInfo.IsThis) return resolvePath;
             if (!pathInfo.IsValidHelperLiteral && !configuration.Compatibility.RelaxedHelperNaming) return resolvePath;
 
             var pathInfoLight = new PathInfoLight(pathInfo);
             if (!configuration.Helpers.TryGetValue(pathInfoLight, out var helper))
             {
                 // TODO: use IHelperResolver here as well
                 var lateBindHelperDescriptor = new LateBindHelperDescriptor(pathInfo);
                 helper = new Ref<IHelperDescriptor<HelperOptions>>(lateBindHelperDescriptor);
                 configuration.Helpers.AddOrReplace(pathInfoLight, helper);
             }
+            else if (helper.Value is LateBindHelperDescriptor existingLateBindHelper
+                     && !string.Equals(existingLateBindHelper.Name.Path, pathInfo.Path, System.StringComparison.Ordinal))
+            {
+                // The helpers dictionary uses case-insensitive keys, so "TEST" and "test" map to the
+                // same slot. If the cached LateBindHelperDescriptor was stored for a differently-cased
+                // path, create a new one that carries the exact casing of the current expression so
+                // that runtime property lookup resolves to the right member.
+                var lateBindHelperDescriptor = new LateBindHelperDescriptor(pathInfo);
+                helper = new Ref<IHelperDescriptor<HelperOptions>>(lateBindHelperDescriptor);
+            }
             else if (configuration.Compatibility.RelaxedHelperNaming)
             {
                 pathInfoLight = pathInfoLight.TagComparer();
                 if (!configuration.Helpers.ContainsKey(pathInfoLight))