Make ToString() valid without a type registry

This addresses issue #1008, by creating a JsonFormatter which is private and only different
to JsonFormatter.Default in terms of reference equality.

Other plausible designs:

- The same, but expose the diagnostic-only formatter
- Add something to settings to say "I don't have a type registry at all"
- Change the behaviour of JsonFormatter.Default (bad idea IMO, as we really *don't* want the result of this used as regular JSON to be parsed)

Note that just trying to find a separate fix to issue #933 and using that to override Any.ToString() differently wouldn't work for messages that *contain* an Any.

Generated code changes follow in the next commit.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/google/protobuf/compiler/csharp/csharp_message.cc b/src/google/protobuf/compiler/csharp/csharp_message.cc
index 9c72043b..e0230a24 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_message.cc
@@ -353,7 +353,7 @@ void MessageGenerator::GenerateFrameworkMethods(io::Printer* printer) {
 
     printer->Print(
         "public override string ToString() {\n"
-        "  return pb::JsonFormatter.Default.Format(this);\n"
+        "  return pb::JsonFormatter.ToDiagnosticString(this);\n"
         "}\n\n");
 }