diff --git a/csharp/src/AddressBook/Addressbook.cs b/csharp/src/AddressBook/Addressbook.cs
index d5455d8078..2c81004c5b 100644
--- a/csharp/src/AddressBook/Addressbook.cs
+++ b/csharp/src/AddressBook/Addressbook.cs
@@ -43,6 +43,9 @@ namespace Google.Protobuf.Examples.AddressBook {
 
   }
   #region Messages
+  /// <summary>
+  ///  [START messages]
+  /// </summary>
   [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
   public sealed partial class Person : pb::IMessage<Person> {
     private static readonly pb::MessageParser<Person> _parser = new pb::MessageParser<Person>(() => new Person());
@@ -143,7 +146,7 @@ namespace Google.Protobuf.Examples.AddressBook {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -302,7 +305,7 @@ namespace Google.Protobuf.Examples.AddressBook {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -426,7 +429,7 @@ namespace Google.Protobuf.Examples.AddressBook {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Conformance/Conformance.cs b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
index 50ce1de4f7..f135d7684a 100644
--- a/csharp/src/Google.Protobuf.Conformance/Conformance.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
@@ -284,7 +284,7 @@ namespace Conformance {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -532,7 +532,7 @@ namespace Conformance {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1544,7 +1544,7 @@ namespace Conformance {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2343,7 +2343,7 @@ namespace Conformance {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -2471,7 +2471,7 @@ namespace Conformance {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
index 5ff47ed253..3e9999e4de 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
@@ -425,7 +425,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -633,7 +633,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -741,7 +741,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -851,7 +851,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1121,7 +1121,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1318,7 +1318,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1427,7 +1427,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
index f257b46ca2..72ada3de2c 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
@@ -110,7 +110,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
index 2881ca0f87..45f0e247c6 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
@@ -96,7 +96,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
index cf34e8bccd..9ac2d7ac15 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
@@ -126,7 +126,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -204,7 +204,7 @@ namespace UnitTest.Issues.TestProtos {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -282,7 +282,7 @@ namespace UnitTest.Issues.TestProtos {
             }
 
             public override string ToString() {
-              return pb::JsonFormatter.Default.Format(this);
+              return pb::JsonFormatter.ToDiagnosticString(this);
             }
 
             public void WriteTo(pb::CodedOutputStream output) {
@@ -405,7 +405,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -511,7 +511,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -668,7 +668,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -831,7 +831,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -947,7 +947,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1056,7 +1056,7 @@ namespace UnitTest.Issues.TestProtos {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -1279,7 +1279,7 @@ namespace UnitTest.Issues.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
index 04de603b8d..462ae9f95f 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
@@ -927,7 +927,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1600,7 +1600,7 @@ namespace Google.Protobuf.TestProtos {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -1736,7 +1736,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1873,7 +1873,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1980,7 +1980,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2070,7 +2070,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2162,7 +2162,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2291,7 +2291,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2421,7 +2421,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2547,7 +2547,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2669,7 +2669,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2883,7 +2883,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3107,7 +3107,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3278,7 +3278,7 @@ namespace Google.Protobuf.TestProtos {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -3400,7 +3400,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3506,7 +3506,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3608,7 +3608,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3704,7 +3704,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3807,7 +3807,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3913,7 +3913,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4016,7 +4016,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4119,7 +4119,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4222,7 +4222,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4325,7 +4325,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4486,7 +4486,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4780,7 +4780,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5140,7 +5140,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5414,7 +5414,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5554,7 +5554,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5647,7 +5647,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5723,7 +5723,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5799,7 +5799,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5875,7 +5875,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5951,7 +5951,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -6027,7 +6027,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
index 642e5f9126..c00b0f41c6 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
@@ -466,7 +466,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1106,7 +1106,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1625,7 +1625,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2213,7 +2213,7 @@ namespace Google.Protobuf.TestProtos {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
index 03685322a4..d29424ada4 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
@@ -225,7 +225,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -489,7 +489,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -827,7 +827,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1021,7 +1021,7 @@ namespace Google.Protobuf.Reflection {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -1162,7 +1162,7 @@ namespace Google.Protobuf.Reflection {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -1436,7 +1436,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1741,7 +1741,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1872,7 +1872,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2031,7 +2031,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2196,7 +2196,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2404,7 +2404,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -2863,7 +2863,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3302,7 +3302,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3596,7 +3596,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3845,7 +3845,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -3990,7 +3990,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4121,7 +4121,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4252,7 +4252,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4451,7 +4451,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -4653,7 +4653,7 @@ namespace Google.Protobuf.Reflection {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
@@ -4823,7 +4823,7 @@ namespace Google.Protobuf.Reflection {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -5051,7 +5051,7 @@ namespace Google.Protobuf.Reflection {
         }
 
         public override string ToString() {
-          return pb::JsonFormatter.Default.Format(this);
+          return pb::JsonFormatter.ToDiagnosticString(this);
         }
 
         public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
index 0b830b668b..efa60a6840 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
@@ -165,7 +165,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
index e9330e6932..1b925b9cbc 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
@@ -230,7 +230,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -503,7 +503,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -783,7 +783,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
index 42fda452d6..4eeff4f033 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
@@ -164,7 +164,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
index 92bc039734..d568a811df 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
@@ -94,7 +94,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
index 963b72bec1..0cd5952a5d 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
@@ -221,7 +221,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
index d53856427b..2972b34601 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
@@ -105,7 +105,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
index 73e3cae294..a811ea8b3f 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
@@ -136,7 +136,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -361,7 +361,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -555,7 +555,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
index 499b095006..adee4bb4c0 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
@@ -175,7 +175,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
index ef368bd392..a76d02b4c7 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
@@ -230,7 +230,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -522,7 +522,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -910,7 +910,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1098,7 +1098,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1244,7 +1244,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
index a70b2fb026..4314877273 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
@@ -117,7 +117,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -228,7 +228,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -339,7 +339,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -450,7 +450,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -561,7 +561,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -672,7 +672,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -783,7 +783,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -894,7 +894,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {
@@ -1005,7 +1005,7 @@ namespace Google.Protobuf.WellKnownTypes {
     }
 
     public override string ToString() {
-      return pb::JsonFormatter.Default.Format(this);
+      return pb::JsonFormatter.ToDiagnosticString(this);
     }
 
     public void WriteTo(pb::CodedOutputStream output) {