From f437b67f600545f432863457a39870cb74675d34 Mon Sep 17 00:00:00 2001
From: Jon Skeet <jonskeet@google.com>
Date: Fri, 15 Jan 2016 12:02:07 +0000
Subject: Extra strictness for FieldMask conversion

---
 csharp/src/Google.Protobuf/JsonFormatter.cs | 27 ++++++++++++++++++++++++++-
 csharp/src/Google.Protobuf/JsonParser.cs    |  8 +++++++-
 2 files changed, 33 insertions(+), 2 deletions(-)

(limited to 'csharp/src/Google.Protobuf')

diff --git a/csharp/src/Google.Protobuf/JsonFormatter.cs b/csharp/src/Google.Protobuf/JsonFormatter.cs
index 563b834e..573ca766 100644
--- a/csharp/src/Google.Protobuf/JsonFormatter.cs
+++ b/csharp/src/Google.Protobuf/JsonFormatter.cs
@@ -224,6 +224,31 @@ namespace Google.Protobuf
             return !first;
         }
 
+        /// <summary>
+        /// Camel-case converter with added strictness for field mask formatting.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">The field mask is invalid for JSON representation</exception>
+        private static string ToCamelCaseForFieldMask(string input)
+        {
+            for (int i = 0; i < input.Length; i++)
+            {
+                char c = input[i];
+                if (c >= 'A' && c <= 'Z')
+                {
+                    throw new InvalidOperationException($"Invalid field mask to be converted to JSON: {input}");
+                }
+                if (c == '_' && i < input.Length - 1)
+                {
+                    char next = input[i + 1];
+                    if (next < 'a' || next > 'z')
+                    {
+                        throw new InvalidOperationException($"Invalid field mask to be converted to JSON: {input}");
+                    }
+                }
+            }
+            return ToCamelCase(input);
+        }
+
         // Converted from src/google/protobuf/util/internal/utility.cc ToCamelCase
         // TODO: Use the new field in FieldDescriptor.
         internal static string ToCamelCase(string input)
@@ -525,7 +550,7 @@ namespace Google.Protobuf
         private void WriteFieldMask(StringBuilder builder, IMessage value)
         {
             IList paths = (IList) value.Descriptor.Fields[FieldMask.PathsFieldNumber].Accessor.GetValue(value);
-            WriteString(builder, string.Join(",", paths.Cast<string>().Select(ToCamelCase)));
+            WriteString(builder, string.Join(",", paths.Cast<string>().Select(ToCamelCaseForFieldMask)));
         }
 
         private void WriteAny(StringBuilder builder, IMessage value)
diff --git a/csharp/src/Google.Protobuf/JsonParser.cs b/csharp/src/Google.Protobuf/JsonParser.cs
index db601c57..9e5d8711 100644
--- a/csharp/src/Google.Protobuf/JsonParser.cs
+++ b/csharp/src/Google.Protobuf/JsonParser.cs
@@ -894,6 +894,8 @@ namespace Google.Protobuf
         private static string ToSnakeCase(string text)
         {
             var builder = new StringBuilder(text.Length * 2);
+            // Note: this is probably unnecessary now, but currently retained to be as close as possible to the
+            // C++, whilst still throwing an exception on underscores.
             bool wasNotUnderscore = false;  // Initialize to false for case 1 (below)
             bool wasNotCap = false;
 
@@ -927,7 +929,11 @@ namespace Google.Protobuf
                 else
                 {
                     builder.Append(c);
-                    wasNotUnderscore = c != '_';
+                    if (c == '_')
+                    {
+                        throw new InvalidProtocolBufferException($"Invalid field mask: {text}");
+                    }
+                    wasNotUnderscore = true;
                     wasNotCap = true;
                 }
             }
-- 
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