[C++] Generate message pretty printers

[arnetheduck]

It would be very convenient if the generated code could also pretty print (to string, ostream or whatever) in some suitable name=value format (FIX, json, protobuf ShortDebugString to name a few candidates), for debugging / logging purposes.

[tmontgomery]

Marking as an enhancement. This could be quite nice.

[donmendelson]

For debugging, essential features for pretty print include printing symbolic names for enum values and bits of a bitset.

More broadly, useful interpretation of an encoding requires knowing its semanticType (application layer class). For example, a decimal is encoded as a composite type of mantissa and exponent. The print function should not show it as two separate elements, but rather as a properly formatted decimal number with correct precision. Likewise, a UTCTimestamp field should be formatted as a data/time rather than the integer sent on the wire. This implies registering a toString() function for each semantic type or encoding.

[lcs777]

I dipped my toe in the water with PR #296 . I am thinking of expanding this work by adding the ability to print to an ostream (for enums, options, decimals) as well as having a toJson() method for each message, since JSON seems the most useful human readable encoding.

If anyone has any suggestions, please let me know.

[MatthiasKauer]

Hi,
I'm interested in working on this.
Is it still relevant? Is someone else working on it?

[mjpt777]

@MatthiasKauer We would be happy accepting a PR for this.