json pretty printer for gdb

gistfile1.txt

(gdb) p -pretty on -array on -- mixed_nested
$1 = std::map with 5 elements = {
  ["Baptiste"] = std::map with 1 element = {
    ["first"] = "second"
  },
  ["Emmanuel"] = std::vector of length 3, capacity 3 = {
    3,
    "25",
    0.5
  },
  ["Jean"] = 0.7,
  ["Zorg"] = std::map with 8 elements = {
    ["array"] = std::vector of length 3, capacity 3 = {
      1,
      0,
      2
    },
    ["awesome_str"] = "bleh",
    ["bool"] = true,
    ["flex"] = 0.2,
    ["float"] = 5.22,
    ["int"] = 5,
    ["nested"] = std::map with 1 element = {
      ["bar"] = "barz"
    },
    ["trap "] = "you fell"
  },
  ["empty"] = nlohmann::detail::value_t::null
}

nlohmann-json.py

import gdb
import re

class JsonValuePrinter:
    "Print a json-value"

    def __init__(self, val):
        self.val = val

    def to_string(self):
        if self.val.type.strip_typedefs().code == gdb.TYPE_CODE_FLT:
            return ("%.6f" % float(self.val)).rstrip("0")
        return self.val

def json_lookup_function(val):
    if re.search("^nlohmann::basic_json<.*>$", val.type.strip_typedefs().name):
        t = str(val['m_type'])
        if t.startswith("nlohmann::detail::value_t::"):
            try:
                union_val = val['m_value'][t[27:]]
                if union_val.type.code == gdb.TYPE_CODE_PTR:
                    return gdb.default_visualizer(union_val.dereference())
                else:
                    return JsonValuePrinter(union_val)
            except:
                return JsonValuePrinter(val['m_type'])

gdb.pretty_printers.append(json_lookup_function)