Created a new exception for JSON failures.

This is only thrown directly by JsonTokenizer, but surfaces from JsonParser as well. I've added doc comments to hopefully make everything clear.

The exception is actually thrown by the reader within JsonTokenizer, in anticipation of keeping track of the location within the document, but that change is not within this PR.

5 files changed, 86 insertions, 16 deletions

diff --git a/csharp/src/Google.Protobuf/Google.Protobuf.csproj b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
index 00399438..24fe7746 100644
--- a/csharp/src/Google.Protobuf/Google.Protobuf.csproj
+++ b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
@@ -84,6 +84,7 @@
     <Compile Include="FieldCodec.cs" />

     <Compile Include="FrameworkPortability.cs" />

     <Compile Include="IDeepCloneable.cs" />

+    <Compile Include="InvalidJsonException.cs" />

     <Compile Include="JsonFormatter.cs" />

     <Compile Include="JsonParser.cs" />

     <Compile Include="JsonToken.cs" />

diff --git a/csharp/src/Google.Protobuf/InvalidJsonException.cs b/csharp/src/Google.Protobuf/InvalidJsonException.cs
new file mode 100644
index 00000000..b5434201
--- /dev/null
+++ b/csharp/src/Google.Protobuf/InvalidJsonException.cs
@@ -0,0 +1,53 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System.IO;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Thrown when an attempt is made to parse invalid JSON, e.g. using
+    /// a non-string property key, or including a redundant comma. Parsing a protocol buffer
+    /// message represented in JSON using <see cref="JsonParser"/> can throw both this
+    /// exception and <see cref="InvalidProtocolBufferException"/> depending on the situation. This
+    /// exception is only thrown for "pure JSON" errors, whereas <c>InvalidProtocolBufferException</c>
+    /// is thrown when the JSON may be valid in and of itself, but cannot be parsed as a protocol buffer
+    /// message.
+    /// </summary>
+    public sealed class InvalidJsonException : IOException
+    {
+        internal InvalidJsonException(string message)
+            : base(message)
+        {
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/src/Google.Protobuf/JsonParser.cs b/csharp/src/Google.Protobuf/JsonParser.cs
index 6d2638d9..8da57745 100644
--- a/csharp/src/Google.Protobuf/JsonParser.cs
+++ b/csharp/src/Google.Protobuf/JsonParser.cs
@@ -337,6 +337,8 @@ namespace Google.Protobuf
         /// </summary>
         /// <typeparam name="T">The type of message to create.</typeparam>
         /// <param name="json">The JSON to parse.</param>
+        /// <exception cref="InvalidJsonException">The JSON does not comply with RFC 7159</exception>
+        /// <exception cref="InvalidProtocolBufferException">The JSON does not represent a Protocol Buffers message correctly</exception>
         public T Parse<T>(string json) where T : IMessage, new()
         {
             return Parse<T>(new StringReader(json));
@@ -347,6 +349,8 @@ namespace Google.Protobuf
         /// </summary>
         /// <typeparam name="T">The type of message to create.</typeparam>
         /// <param name="jsonReader">Reader providing the JSON to parse.</param>
+        /// <exception cref="InvalidJsonException">The JSON does not comply with RFC 7159</exception>
+        /// <exception cref="InvalidProtocolBufferException">The JSON does not represent a Protocol Buffers message correctly</exception>
         public T Parse<T>(TextReader jsonReader) where T : IMessage, new()
         {
             T message = new T();
diff --git a/csharp/src/Google.Protobuf/JsonTokenizer.cs b/csharp/src/Google.Protobuf/JsonTokenizer.cs
index 108ccebe..5ed1e449 100644
--- a/csharp/src/Google.Protobuf/JsonTokenizer.cs
+++ b/csharp/src/Google.Protobuf/JsonTokenizer.cs
@@ -88,6 +88,7 @@ namespace Google.Protobuf
         /// </remarks>
         /// <returns>The next token in the stream. This is never null.</returns>
         /// <exception cref="InvalidOperationException">This method is called after an EndDocument token has been returned</exception>
+        /// <exception cref="InvalidJsonException">The input text does not comply with RFC 7159</exception>
         internal JsonToken Next()
         {
             if (bufferedToken != null)
@@ -182,7 +183,7 @@ namespace Google.Protobuf
                         ValidateAndModifyStateForValue("Invalid state to read a number token: ");
                         return JsonToken.Value(number);
                     default:
-                        throw new InvalidProtocolBufferException("Invalid first character of token: " + next.Value);
+                        throw new InvalidJsonException("Invalid first character of token: " + next.Value);
                 }
             }
         }
@@ -191,7 +192,7 @@ namespace Google.Protobuf
         {
             if ((validStates & state) == 0)
             {
-                throw new InvalidProtocolBufferException(errorPrefix + state);
+                throw reader.CreateException(errorPrefix + state);
             }
         }
 
@@ -207,13 +208,13 @@ namespace Google.Protobuf
                 char c = reader.ReadOrFail("Unexpected end of text while reading string");
                 if (c < ' ')
                 {
-                    throw new InvalidProtocolBufferException(string.Format(CultureInfo.InvariantCulture, "Invalid character in string literal: U+{0:x4}", (int) c));
+                    throw reader.CreateException(string.Format(CultureInfo.InvariantCulture, "Invalid character in string literal: U+{0:x4}", (int) c));
                 }
                 if (c == '"')
                 {
                     if (haveHighSurrogate)
                     {
-                        throw new InvalidProtocolBufferException("Invalid use of surrogate pair code units");
+                        throw reader.CreateException("Invalid use of surrogate pair code units");
                     }
                     return value.ToString();
                 }
@@ -226,7 +227,7 @@ namespace Google.Protobuf
                 // followed by an escaped low surrogate or vice versa... and that couldn't even be represented in UTF-8.
                 if (haveHighSurrogate != char.IsLowSurrogate(c))
                 {
-                    throw new InvalidProtocolBufferException("Invalid use of surrogate pair code units");
+                    throw reader.CreateException("Invalid use of surrogate pair code units");
                 }
                 haveHighSurrogate = char.IsHighSurrogate(c);
                 value.Append(c);
@@ -260,7 +261,7 @@ namespace Google.Protobuf
                 case 'u':
                     return ReadUnicodeEscape();
                 default:
-                    throw new InvalidProtocolBufferException(string.Format(CultureInfo.InvariantCulture, "Invalid character in character escape sequence: U+{0:x4}", (int) c));
+                    throw reader.CreateException(string.Format(CultureInfo.InvariantCulture, "Invalid character in character escape sequence: U+{0:x4}", (int) c));
             }
         }
 
@@ -288,7 +289,7 @@ namespace Google.Protobuf
                 }
                 else
                 {
-                    throw new InvalidProtocolBufferException(string.Format(CultureInfo.InvariantCulture, "Invalid character in character escape sequence: U+{0:x4}", (int) c));
+                    throw reader.CreateException(string.Format(CultureInfo.InvariantCulture, "Invalid character in character escape sequence: U+{0:x4}", (int) c));
                 }
                 result = (result << 4) + nybble;
             }
@@ -306,11 +307,11 @@ namespace Google.Protobuf
                 char? next = reader.Read();
                 if (next == null)
                 {
-                    throw new InvalidProtocolBufferException("Unexpected end of text while reading literal token " + text);
+                    throw reader.CreateException("Unexpected end of text while reading literal token " + text);
                 }
                 if (next.Value != text[i])
                 {
-                    throw new InvalidProtocolBufferException("Unexpected character while reading literal token " + text);
+                    throw reader.CreateException("Unexpected character while reading literal token " + text);
                 }
             }
         }
@@ -354,7 +355,7 @@ namespace Google.Protobuf
             }
             catch (OverflowException)
             {
-                throw new InvalidProtocolBufferException("Numeric value out of range: " + builder);
+                throw reader.CreateException("Numeric value out of range: " + builder);
             }
         }
 
@@ -363,14 +364,14 @@ namespace Google.Protobuf
             char first = reader.ReadOrFail("Invalid numeric literal");
             if (first < '0' || first > '9')
             {
-                throw new InvalidProtocolBufferException("Invalid numeric literal");
+                throw reader.CreateException("Invalid numeric literal");
             }
             builder.Append(first);
             int digitCount;
             char? next = ConsumeDigits(builder, out digitCount);
             if (first == '0' && digitCount != 0)
             {
-                throw new InvalidProtocolBufferException("Invalid numeric literal: leading 0 for non-zero value.");
+                throw reader.CreateException("Invalid numeric literal: leading 0 for non-zero value.");
             }
             return next;
         }
@@ -382,7 +383,7 @@ namespace Google.Protobuf
             char? next = ConsumeDigits(builder, out digitCount);
             if (digitCount == 0)
             {
-                throw new InvalidProtocolBufferException("Invalid numeric literal: fraction with no trailing digits");
+                throw reader.CreateException("Invalid numeric literal: fraction with no trailing digits");
             }
             return next;
         }
@@ -393,7 +394,7 @@ namespace Google.Protobuf
             char? next = reader.Read();
             if (next == null)
             {
-                throw new InvalidProtocolBufferException("Invalid numeric literal: exponent with no trailing digits");
+                throw reader.CreateException("Invalid numeric literal: exponent with no trailing digits");
             }
             if (next == '-' || next == '+')
             {
@@ -407,7 +408,7 @@ namespace Google.Protobuf
             next = ConsumeDigits(builder, out digitCount);
             if (digitCount == 0)
             {
-                throw new InvalidProtocolBufferException("Invalid numeric literal: exponent without value");
+                throw reader.CreateException("Invalid numeric literal: exponent without value");
             }
             return next;
         }
@@ -615,7 +616,7 @@ namespace Google.Protobuf
                 char? next = Read();
                 if (next == null)
                 {
-                    throw new InvalidProtocolBufferException(messageOnFailure);
+                    throw CreateException(messageOnFailure);
                 }
                 return next.Value;
             }
@@ -628,6 +629,15 @@ namespace Google.Protobuf
                 }
                 nextChar = c;
             }
+
+            /// <summary>
+            /// Creates a new exception appropriate for the current state of the reader.
+            /// </summary>
+            internal InvalidJsonException CreateException(string message)
+            {
+                // TODO: Keep track of and use the location.
+                return new InvalidJsonException(message);
+            }
         }
     }
 }
diff --git a/csharp/src/Google.Protobuf/MessageParser.cs b/csharp/src/Google.Protobuf/MessageParser.cs
index 70c52ba6..8f2717c5 100644
--- a/csharp/src/Google.Protobuf/MessageParser.cs
+++ b/csharp/src/Google.Protobuf/MessageParser.cs
@@ -148,6 +148,8 @@ namespace Google.Protobuf
         /// </summary>
         /// <param name="json">The JSON to parse.</param>
         /// <returns>The parsed message.</returns>
+        /// <exception cref="InvalidJsonException">The JSON does not comply with RFC 7159</exception>
+        /// <exception cref="InvalidProtocolBufferException">The JSON does not represent a Protocol Buffers message correctly</exception>
         public T ParseJson(string json)
         {
             T message = factory();