Print any lua value as a readable string

inspect.lua

---Inspect a value
---
---Converts nil, boolean, number, string or table to string
---Any other type is converted with `tostring`.
---
---List-like tables are printed without their indices
---
---Usage:
---
---```lua
---print(1, Inspect(nil))
---print(2, Inspect(true))
---print(3, Inspect(27.9))
---print(4, Inspect("hello world"))
---print(5, Inspect("hello\n\tworld"))
---print(6, Inspect({ 1, "2", 3 }))
---print(7, Inspect({ [{ a = 1, b = 4 }] = { 1, 2, 3 }, x = false, [4] = { x = 1, y = 2, ["a\tb"] = 3 } }))
---```
---
---Output:
---```
---1   nil
---2   true
---3   27.9
---4   "hello world"
---5   "hello\n\tworld"
---6   [1, "2", 3]
---7   {
---    x = false,
---    [4] = {
---        x = 1,
---        y = 2,
---        ["a\tb"] = 3,
---    },
---    [{
---        b = 4,
---        a = 1,
---    }] = [1, 2, 3],
---}
---```
---@param v any
---@param indent nil
---@return string
function Inspect(v, indent)
    if indent == nil then indent = 0 end
    local function is_list(tbl)
        local prev = 0
        for key, value in pairs(tbl) do
            prev = prev + 1
            if key ~= prev then return false end
        end
        return true
    end
    ---@param str string
    ---@return string
    ---@return boolean
    local function escape(str)
        local escape_chars = {
            ["\n"] = "\\n",
            ["\t"] = "\\t",
            ["\\"] = "\\\\",
            ["\""] = "\\\"",
            ["\'"] = "\\\'",
        }
        local out = str:gsub(".", function(char) return escape_chars[char] or char end)
        return out, out ~= str
    end
    if type(v) == "nil" then return "nil" end
    if type(v) == "string" then return '"' .. escape(v) .. '"' end
    if type(v) == "table" then
        if is_list(v) then
            if rawequal(next(v), nil) then return "{}" end
            local outstr = ""
            outstr = '[' .. Inspect(v[1], indent)
            for i = 2, #v do
                outstr = outstr .. ", " .. Inspect(v[i], indent)
            end
            return outstr .. ']'
        else
            local outstr = ""
            outstr = '{\n'
            for key, value in pairs(v) do
                local keystr = (function()
                    if type(key) == "string" then
                        local _, escaped = escape(key)
                        if not escaped then return key end
                    end
                    return "[" .. Inspect(key, indent + 1) .. "]"
                end)()
                outstr = outstr ..
                    string.rep("    ", indent + 1) .. keystr .. " = " .. Inspect(value, indent + 1) .. ",\n"
            end
            return outstr .. string.rep("    ", indent) .. '}'
        end
    end
    return tostring(v)
end