XDR-JSON Snake casing has surprising behavior

[drebelsky]

SEP-51 discusses snake_caseing multiple kinds of identifiers, but the specific algorithm is a little unclear. Consider the following

enum IPAddrType
{
    IPv4 = 0,
    IPv6 = 1
};

struct PeerAddress
{
    union switch (IPAddrType type)
    {
    case IPv4:
        opaque ipv4[4];
    case IPv6:
        opaque ipv6[16];
    }
    ip;
    uint32 port;
    uint32 numFailures;
};

$ echo 'AAAAAAAAAAA=' | stellar xdr decode --type PeerAddressIp
{"i_pv4":[0,0,0,0]}
$ echo 'AAAAAAAAAAAAAAAAAAAAAA==' | stellar xdr decode --type PeerAddress
{"ip":{"i_pv4":[0,0,0,0]},"port":0,"num_failures":0}

Note the suboptimal IPv4 to i_pv4 conversion.

[drebelsky]

It's a mixture of serde and activesupport for how this happens.

use serde::{Deserialize, Serialize};
use strum::IntoEnumIterator;
use strum_macros::EnumIter;

#[derive(Serialize, Deserialize, Debug, EnumIter)]
#[serde(rename_all = "snake_case")]
#[allow(non_camel_case_types)]
pub enum Identifiers {
    ipv4,
    IPv4,
    IPV4,
    ID,
    SCREAMING_UPPER_CASE,
    snake_case,
    camelCase,
    PascalCase,
}

fn main() {
    for ident in Identifiers::iter() {
        let serialized = serde_json::to_string(&ident).unwrap();
        println!("{:?} -> {}", ident, serialized);
    }
}

$ cargo run
ipv4 -> "ipv4"
IPv4 -> "i_pv4"
IPV4 -> "i_p_v4"
ID -> "i_d"
SCREAMING_UPPER_CASE -> "s_c_r_e_a_m_i_n_g__u_p_p_e_r__c_a_s_e"
snake_case -> "snake_case"
camelCase -> "camel_case"
PascalCase -> "pascal_case"

require "active_support/inflector"
identifiers = %w[ipv4 IPv4 IPV4 ID SCREAMING_UPPER_CASE snake_case camelCase PascalCase]
identifiers.each do |ident|
  puts "#{ident} -> #{ident.underscore} -> #{ident.underscore.camelize}"
end

ipv4 -> ipv4 -> Ipv4
IPv4 -> i_pv4 -> IPv4
IPV4 -> ipv4 -> Ipv4
ID -> id -> Id
SCREAMING_UPPER_CASE -> screaming_upper_case -> ScreamingUpperCase
snake_case -> snake_case -> SnakeCase
camelCase -> camel_case -> CamelCase
PascalCase -> pascal_case -> PascalCase