Move the creation of the "fields by JSON name" dictionary to the descriptor.

1 files changed, 15 insertions, 0 deletions

diff --git a/csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs b/csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs
index 82901f1b..e599998e 100644
--- a/csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs
@@ -62,6 +62,7 @@ namespace Google.Protobuf.Reflection
         private readonly IList<EnumDescriptor> enumTypes;
         private readonly IList<FieldDescriptor> fieldsInDeclarationOrder;
         private readonly IList<FieldDescriptor> fieldsInNumberOrder;
+        private readonly IDictionary<string, FieldDescriptor> jsonFieldMap;
         private readonly FieldCollection fields;
         private readonly IList<OneofDescriptor> oneofs;
         // CLR representation of the type described by this descriptor, if any.
@@ -95,6 +96,8 @@ namespace Google.Protobuf.Reflection
                 (field, index) =>
                 new FieldDescriptor(field, file, this, index, generatedCodeInfo == null ? null : generatedCodeInfo.PropertyNames[index]));
             fieldsInNumberOrder = new ReadOnlyCollection<FieldDescriptor>(fieldsInDeclarationOrder.OrderBy(field => field.FieldNumber).ToArray());
+            // TODO: Use field => field.Proto.JsonName when we're confident it's appropriate. (And then use it in the formatter, too.)
+            jsonFieldMap = new ReadOnlyDictionary<string, FieldDescriptor>(fieldsInNumberOrder.ToDictionary(field => JsonFormatter.ToCamelCase(field.Name)));
             file.DescriptorPool.AddSymbol(this);
             fields = new FieldCollection(this);
         }
@@ -255,6 +258,18 @@ namespace Google.Protobuf.Reflection
                 return messageDescriptor.fieldsInNumberOrder;
             }
 
+            // TODO: consider making this public in the future. (Being conservative for now...)
+
+            /// <value>
+            /// Returns a read-only dictionary mapping the field names in this message as they're used
+            /// in the JSON representation to the field descriptors. For example, a field <c>foo_bar</c>
+            /// in the message would result in an entry with a key <c>fooBar</c>.
+            /// </value>
+            internal IDictionary<string, FieldDescriptor> ByJsonName()
+            {
+                return messageDescriptor.jsonFieldMap;
+            }
+
             /// <summary>
             /// Retrieves the descriptor for the field with the given number.
             /// </summary>