inspect.lua

This function transform any Lua table into a human-readable representation of that table.

The objective here is human understanding (i.e. for debugging), not serialization or compactness.

Examples of use

"Array-like" tables are rendered horizontally:

inspect({1,2,3,4}) == "{ 1, 2, 3, 4 }"

"dictionary-like" tables are rendered with one element per line:

inspect({a=1,b=2}) == [[{
  a = 1,
  b = 2
}]]

The keys will be sorted alphanumerically when possible.

"Hybrid" tables will have the array part on the first line, and the dictionary part just below them:

inspect({1,2,3,b=2,a=1}) == [[{ 1, 2, 3,
  a = 1,
  b = 2
}]]

Tables can be nested, and will be indented with two spaces per level.

inspect({a={b=2}}) == [[{
  a = {
    b = 2
  }
}]]

inspect's second parameter allows controlling the maximum depth that will be printed out. When the max depth is reached, it'll just return {...}:

local t5 = {a = {b = {c = {d = {e = 5}}}}}

inspect(t5, 4) == [[{
  a = {
    b = {
      c = {
        d = {...}
      }
    }
  }
}]]

inspect(t5, 2) == [[{
  a = {
    b = {...}
  }
}]])

Functions, userdata and threads are simply rendered as <function x>, <userdata x> and <thread x> respectively:

inspect({ f = print, ud = some_user_data, thread = a_thread} ) == [[{
  f = <function 1>,
  u = <userdata 1>,
  thread = <thread 1>
}]])

If the table has a metatable, inspect will include it at the end, in a special field called <metatable>:

inspect(setmetatable({a=1}, {b=2}) == [[{
  a = 1
  <metatable> = {
    b = 2
  }
}]])

inspect can handle tables with loops inside them. It will print <id> right before the table is printed out the first time, and replace the whole table with <table id> from then on, preventing infinite loops.

a = {1, 2}
b = {3, 4, a}
a[3] = b -- a references b, and b references a
inspect(a) = "<1>{ 1, 2, { 3, 4, <table 1> } }"

Notice that since both a appears more than once in the expression, it is prefixed by <1> and replaced by <table 1> every time it appears later on.

Gotchas / Warnings

This method is not appropiate for saving/restoring tables. It is ment to be used by the programmer mainly while debugging a program.

Installation

Just copy the inspect.lua file somewhere in your projects (maybe inside a /lib/ folder) and require it accordingly.

Remember to store the value returned by require somewhere! (I suggest a local variable named inspect, altough others might like table.inspect)

local inspect = require 'inspect'
      -- or --
table.inspect = require 'inspect'

Also, make sure to read the license file; the text of that license file must appear somewhere in your projects' files.

Specs

This project uses "telescope":https://github.com/norman/telescope for its specs. If you want to run the specs, you will have to install telescope first. Then just execute the following from the root inspect folder:

tsc -f spec/*