Is Handlebars.Net case sensitive again? #362

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1. oformaniuk commented on Sep 24, 2020

   

   oformaniuk

   on Sep 24, 2020

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   Hello @brandon-vs . Unfortunately not everything can be handled in case-insensitive way. For example consider data object implementing IDictionary<string, object> (applies to your example with ExpandoObject) - in order to get value from the object members of IDictionary<string, object> will be used. If data source provide case-insensitive access to properties (e.g. new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase)) you'd get case-insensitive behavior. The same is true for POCOs as the library performs case-insensitive property search.
   Unfortunately the library is not able to handle cases when IDictionary<string, object> data source does not provide case-insensitive behavior as it would require wrapping such object with some kind of proxy that would handle case-insensitive search. Including such functionality as a default behavior can impact performance.

   However starting from 2.0 you would be able to handle such problems on you own by registering custom IObjectDescriptorProvider:

   [Fact]
   public void CaseInsensitiveExpandoObject()
   {
       var templateString = "Dear {{displayName}}";
       var configuration = new HandlebarsConfiguration();
       configuration.CompileTimeConfiguration.ObjectDescriptorProviders.Add(new ExpandoObjectDescriptor());
       var handlebars = Handlebars.Create(configuration);
       var template = handlebars.Compile(templateString);
   
       var data = new ExpandoObject();
       data.TryAdd("DisplayName", "John");
   
       var output = template(data);
   
       Assert.Equal("Dear John", output);
   }
   
   public class ExpandoObjectDescriptor : IObjectDescriptorProvider
   {
       public bool CanHandleType(Type type)
       {
           return typeof(ExpandoObject).IsAssignableFrom(type);
       }
   
       public bool TryGetDescriptor(Type type, out ObjectDescriptor value)
       {
           if (!typeof(ExpandoObject).IsAssignableFrom(type))
           {
               value = ObjectDescriptor.Empty;;
               return false;
           }
           
           value = new ObjectDescriptor(
               type, 
               new ExpandoObjectMemberAccessor(), 
               (descriptor, o) => ((IDynamicMetaObjectProvider)o).GetMetaObject(Expression.Constant(o)).GetDynamicMemberNames()
               );
   
           return true;
       }
       
       private class ExpandoObjectMemberAccessor : IMemberAccessor
       {
           public bool TryGetValue(object instance, Type instanceType, string memberName, out object value)
           {
               if (instance is ExpandoObject expandoObject)
               {
                   var invariant = memberName.ToUpperInvariant();
                   var property = ((IDynamicMetaObjectProvider) expandoObject)
                       .GetMetaObject(Expression.Constant(expandoObject))
                       .GetDynamicMemberNames()
                       .FirstOrDefault(o => o.ToUpperInvariant() == invariant);
   
                   if (property != null)
                   {
                       value = ((IDictionary<string, object>) expandoObject)[property];
                       return true;
                   }
               }
   
               value = null;
               return false;
           }
       }
   }

   Be aware that proposed API is not final and may change prior to v2 release.
3. ghost closed this as completedon Sep 24, 2020
4. Handlebars-Net

   locked and limited conversation to collaborators on Jan 24, 2022
5. oformaniuk

   converted this issue into a discussion #491 on Jan 24, 2022