Protobuf: C++ JSON parser incorrectly accepts lowercase enum value names.

[xfxyjwf]

Given this proto definition:

enum Category {
    NOT_SPECIFIED = 0;
    LISTINGS = 1;
    REPUTATION = 2;
}

The C++ JSON parser should only accept "LISTINGS" as enum field values, but right now it accepts "listings" (converted to lower-case) as well.

For enum fields, proto3 JSON spec says "The name of the enum value as specified in proto is used":
https://developers.google.com/protocol-buffers/docs/proto3#json

"as specified in proto" should be interpreted as "the exactly same name including casing as specified in proto".

[xfxyjwf]

Apparently C++ JSON parser not only accepts lower-case enum value names, but actually accepts arbitrary casing like "Listings" or "LiStInGs"...

[xfxyjwf]

Well, that only works if the enum name is defined all upper case. If the enum is defined as:

enum Category {
    NotSpecified = 0;
    Listings = 1;
    Reputation = 2;
}

Neither "listings" nor "LISTINGS" will be accepted... With the above definition, only "Listings" works.