mirror of https://github.com/minetest/minetest.git
208 lines
7.7 KiB
Lua
208 lines
7.7 KiB
Lua
-- Minetest: builtin/serialize.lua
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-- https://github.com/fab13n/metalua/blob/no-dll/src/lib/serialize.lua
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-- Copyright (c) 2006-2997 Fabien Fleutot <metalua@gmail.com>
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-- License: MIT
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--------------------------------------------------------------------------------
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-- Serialize an object into a source code string. This string, when passed as
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-- an argument to deserialize(), returns an object structurally identical
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-- to the original one. The following are currently supported:
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-- * strings, numbers, booleans, nil
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-- * tables thereof. Tables can have shared part, but can't be recursive yet.
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-- Caveat: metatables and environments aren't saved.
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--------------------------------------------------------------------------------
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local no_identity = { number=1, boolean=1, string=1, ['nil']=1 }
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function minetest.serialize(x)
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local gensym_max = 0 -- index of the gensym() symbol generator
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local seen_once = { } -- element->true set of elements seen exactly once in the table
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local multiple = { } -- element->varname set of elements seen more than once
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local nested = { } -- transient, set of elements currently being traversed
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local nest_points = { }
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local nest_patches = { }
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local function gensym()
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gensym_max = gensym_max + 1 ; return gensym_max
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end
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-----------------------------------------------------------------------------
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-- nest_points are places where a table appears within itself, directly or not.
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-- for instance, all of these chunks create nest points in table x:
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-- "x = { }; x[x] = 1", "x = { }; x[1] = x", "x = { }; x[1] = { y = { x } }".
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-- To handle those, two tables are created by mark_nest_point:
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-- * nest_points [parent] associates all keys and values in table parent which
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-- create a nest_point with boolean `true'
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-- * nest_patches contain a list of { parent, key, value } tuples creating
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-- a nest point. They're all dumped after all the other table operations
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-- have been performed.
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--
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-- mark_nest_point (p, k, v) fills tables nest_points and nest_patches with
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-- informations required to remember that key/value (k,v) create a nest point
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-- in table parent. It also marks `parent' as occuring multiple times, since
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-- several references to it will be required in order to patch the nest
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-- points.
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-----------------------------------------------------------------------------
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local function mark_nest_point (parent, k, v)
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local nk, nv = nested[k], nested[v]
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assert (not nk or seen_once[k] or multiple[k])
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assert (not nv or seen_once[v] or multiple[v])
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local mode = (nk and nv and "kv") or (nk and "k") or ("v")
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local parent_np = nest_points [parent]
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local pair = { k, v }
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if not parent_np then parent_np = { }; nest_points [parent] = parent_np end
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parent_np [k], parent_np [v] = nk, nv
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table.insert (nest_patches, { parent, k, v })
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seen_once [parent], multiple [parent] = nil, true
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end
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-----------------------------------------------------------------------------
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-- First pass, list the tables and functions which appear more than once in x
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-----------------------------------------------------------------------------
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local function mark_multiple_occurences (x)
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if no_identity [type(x)] then return end
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if seen_once [x] then seen_once [x], multiple [x] = nil, true
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elseif multiple [x] then -- pass
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else seen_once [x] = true end
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if type (x) == 'table' then
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nested [x] = true
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for k, v in pairs (x) do
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if nested[k] or nested[v] then mark_nest_point (x, k, v) else
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mark_multiple_occurences (k)
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mark_multiple_occurences (v)
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end
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end
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nested [x] = nil
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end
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end
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local dumped = { } -- multiply occuring values already dumped in localdefs
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local localdefs = { } -- already dumped local definitions as source code lines
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-- mutually recursive functions:
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local dump_val, dump_or_ref_val
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--------------------------------------------------------------------
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-- if x occurs multiple times, dump the local var rather than the
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-- value. If it's the first time it's dumped, also dump the content
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-- in localdefs.
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--------------------------------------------------------------------
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function dump_or_ref_val (x)
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if nested[x] then return 'false' end -- placeholder for recursive reference
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if not multiple[x] then return dump_val (x) end
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local var = dumped [x]
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if var then return "_[" .. var .. "]" end -- already referenced
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local val = dump_val(x) -- first occurence, create and register reference
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var = gensym()
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table.insert(localdefs, "_["..var.."]="..val)
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dumped [x] = var
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return "_[" .. var .. "]"
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end
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-----------------------------------------------------------------------------
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-- Second pass, dump the object; subparts occuring multiple times are dumped
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-- in local variables which can be referenced multiple times;
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-- care is taken to dump locla vars in asensible order.
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-----------------------------------------------------------------------------
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function dump_val(x)
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local t = type(x)
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if x==nil then return 'nil'
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elseif t=="number" then return tostring(x)
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elseif t=="string" then return string.format("%q", x)
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elseif t=="boolean" then return x and "true" or "false"
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elseif t=="table" then
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local acc = { }
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local idx_dumped = { }
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local np = nest_points [x]
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for i, v in ipairs(x) do
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if np and np[v] then
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table.insert (acc, 'false') -- placeholder
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else
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table.insert (acc, dump_or_ref_val(v))
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end
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idx_dumped[i] = true
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end
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for k, v in pairs(x) do
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if np and (np[k] or np[v]) then
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--check_multiple(k); check_multiple(v) -- force dumps in localdefs
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elseif not idx_dumped[k] then
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table.insert (acc, "[" .. dump_or_ref_val(k) .. "] = " .. dump_or_ref_val(v))
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end
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end
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return "{ "..table.concat(acc,", ").." }"
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else
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error ("Can't serialize data of type "..t)
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end
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end
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local function dump_nest_patches()
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for _, entry in ipairs(nest_patches) do
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local p, k, v = unpack (entry)
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assert (multiple[p])
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local set = dump_or_ref_val (p) .. "[" .. dump_or_ref_val (k) .. "] = " ..
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dump_or_ref_val (v) .. " -- rec "
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table.insert (localdefs, set)
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end
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end
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mark_multiple_occurences (x)
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local toplevel = dump_or_ref_val (x)
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dump_nest_patches()
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if next (localdefs) then
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return "local _={ }\n" ..
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table.concat (localdefs, "\n") ..
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"\nreturn " .. toplevel
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else
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return "return " .. toplevel
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end
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end
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-- Deserialization.
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-- http://stackoverflow.com/questions/5958818/loading-serialized-data-into-a-table
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--
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local function stringtotable(sdata)
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if sdata:byte(1) == 27 then return nil, "binary bytecode prohibited" end
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local f, message = assert(loadstring(sdata))
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if not f then return nil, message end
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setfenv(f, table)
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return f()
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end
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function minetest.deserialize(sdata)
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local table = {}
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local okay,results = pcall(stringtotable, sdata)
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if okay then
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return results
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end
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minetest.log('error', 'minetest.deserialize(): '.. results)
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return nil
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end
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-- Run some unit tests
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local function unit_test()
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function unitTest(name, success)
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if not success then
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error(name .. ': failed')
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end
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end
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unittest_input = {cat={sound="nyan", speed=400}, dog={sound="woof"}}
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unittest_output = minetest.deserialize(minetest.serialize(unittest_input))
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unitTest("test 1a", unittest_input.cat.sound == unittest_output.cat.sound)
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unitTest("test 1b", unittest_input.cat.speed == unittest_output.cat.speed)
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unitTest("test 1c", unittest_input.dog.sound == unittest_output.dog.sound)
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unittest_input = {escapechars="\n\r\t\v\\\"\'", noneuropean="θשׁ٩∂"}
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unittest_output = minetest.deserialize(minetest.serialize(unittest_input))
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unitTest("test 3a", unittest_input.escapechars == unittest_output.escapechars)
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unitTest("test 3b", unittest_input.noneuropean == unittest_output.noneuropean)
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end
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unit_test() -- Run it
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unit_test = nil -- Hide it
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