Module:Repr

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This module contains functions for generating string representations of Lua objects. It is inspired by Python's repr function.

Usage

To use the module, first you have to import it.

local mRepr = require("Module:Repr")

Then you can use the functions it contains. The documentation for each function is below.

repr

This function generates a string representation of any given Lua object. The idea is that if you copy the string this function produces it, and paste it back into a Lua program, then you should be able to reproduce the original object. This doesn't work for all values, but it should hold for simple cases.

For example, mRepr.repr({bool = true, number = 6, str = "hello world"}) will output the string {bool = true, number = 6, str = "hello world"}.

Basic syntax:

mRepr.repr(value)

Full syntax:

mRepr.repr(value, options)

Parameters:

• value: The value to convert to a string. This can be any Lua value. This parameter is optional, and defaults to nil.
• options: A table of options. This parameter is optional.

The following options can be specified in the options table:

• pretty: If true, output the string in "pretty" format (as in pretty-printing). This will add new lines and indentation between table items. If false, format everything on one line. The default is false.
• tabs: If true, indent with tabs; otherwise, indent with spaces. The default is true. This only has an effect if pretty is true.
• spaces: The number of spaces to indent with, if tabs is false. The default is 4. This only has an effect if pretty is true.
• semicolons: If true, table items are separated with semicolons. If false, they are separated with spaces. The default is false.
• sortKeys: If true, sort table keys in lexical order, after other table key formatting has been applied (such as adding square brackets). If false, table keys are output in arbitrary order (the order they are processed by the pairs function). The default is true.
• depth: The indentation depth to output the top-level object at. The default is 0. This only has an effect if pretty is true.

Features:

• The function handles cyclic tables gracefully; when it detects a cycle, the inner table is rendered as {CYCLIC}.
• __tostring metamethods are automatically called if they are available.
• The sequence part of a table is always rendered as a sequence. If there are also key-value pairs, they will be rendered after the sequence part.

Here is an example that shows off all the bells and whistles:

local myTable = {
	hello = "repr",
	usefulness = 100,
	isEasyToUse = true,
	sequence = {"a", "sequence", "table"},
	mixed = {"a", "sequence", with = "key-value pairs"},
	subTables = {
		moreInfo = "Calls itself recursively on sub-tables"
	},
	usesToString = setmetatable({}, {__tostring = function () return "__tostring functions are called automatically" end}),
	["$YMBOL$"] = "Keys that aren't Lua identifiers are quoted";
	[{also = "Tables as keys work too";}] = "in case you need that",
	cyclic = {note = "cyclical tables are printed as just {CYCLIC}"}
}
myTable.cyclic.cyclic = myTable.cyclic  -- Create a cycle
 
local options = {
	pretty = true,      -- print with \n and indentation?
	semicolons = false, -- when printing tables, use semicolons (;) instead of commas (,)?
	sortKeys = true,    -- when printing dictionary tables, sort keys alphabetically?
	spaces = 3,         -- when pretty printing, use how many spaces to indent?
	tabs = false,       -- when pretty printing, use tabs instead of spaces?
	depth = 0,          -- when pretty pretty printing, what level to start indenting at?
}
mw.log(mRepr.repr(myTable, options))

This logs the following:

{
   ["$YMBOL$"] = "Keys that aren't Lua identifiers are quoted",
   [{
      also = "Tables as keys work too"
   }] = "in case you need that",
   cyclic = {
      cyclic = {CYCLIC},
      note = "cyclical tables are printed as just {CYCLIC}"
   },
   hello = "repr",
   isEasyToUse = true,
   mixed = {
      "a",
      "sequence",
      with = "key-value pairs"
   },
   sequence = {
      "a",
      "sequence",
      "table"
   },
   subTables = {
      moreInfo = "Calls itself recursively on sub-tables"
   },
   usefulness = 100,
   usesToString = __tostring functions are called automatically
}

invocationRepr

This function generates a string representation of a function invocation.

Basic syntax:

mRepr.invocationRepr{funcName = functionName, args = functionArgs}

Full syntax:

mRepr.invocationRepr{funcName = functionName, args = functionArgs, options = options}

Parameters:

• funcName: The function name. This parameter is required, and must be a string.
• args: The function arguments. This should be sequence table. The sequence items can be any Lua value, and will each be rendered using the [[#repr|]] function. This argument is optional.
• options: A table of options. The options are the same as for the repr function. This argument is optional.

Examples:

mRepr.invocationRepr{funcName = "myFunc", args = {"test", 4, true, {"a", "b", "c"}}}

Result: myFunc("test", 4, true, {"a", "b", "c"})

The above documentation is transcluded from Module:Repr/doc. (edit | history)
Editors can experiment in this module's sandbox (create | mirror) and testcases (edit | run) pages.
Subpages of this module.

require('Module:No globals')

local defaultSettings = {
	pretty = false;
	tabs = true;
	semicolons = false;
	spaces = 4;
	sortKeys = true;
}

-- Define the reprRecursive variable here so that we can call the reprRecursive
-- function from renderSequence and renderKeyValueTable without getting
-- "Tried to read nil global reprRecursive" errors.
local reprRecursive

-- lua keywords
local keywords = {
	["and"]      = true,
	["break"]    = true,
	["do"]       = true,
	["else"]     = true,
	["elseif"]   = true,
	["end"]      = true,
	["false"]    = true,
	["for"]      = true,
	["function"] = true,
	["if"]       = true,
	["in"]       = true,
	["local"]    = true,
	["nil"]      = true,
	["not"]      = true,
	["or"]       = true,
	["repeat"]   = true,
	["return"]   = true,
	["then"]     = true,
	["true"]     = true,
	["until"]    = true,
	["while"]    = true,
}
 
local function isLuaIdentifier(str)
	return type(str) == "string"
		-- must be nonempty
		and str:len() > 0
		-- can only contain a-z, A-Z, 0-9 and underscore
		and not str:find("[^%d%a_]")
		-- cannot begin with digit
		and not tonumber(str:sub(1, 1))
		-- cannot be keyword
		and not keywords[str]
end

local function renderString(s)
	return (("%q"):format(s):gsub("\\\n", "\\n"))
end

local function renderNumber(n)
	if n == math.huge then
		return "math.huge"
	elseif n == -math.huge then
		return "-math.huge"
	else
		return tostring(n)
	end
end

local function hasTostringMetamethod(t)
	return getmetatable(t) and type(getmetatable(t).__tostring) == "function"
end


local function isPositiveInteger(value)
	return type(value) == "number"
		and value >= 1
		and value < math.huge
		and value == math.floor(value)
end

local function isSequence(t)
	for k in pairs(t) do
		if not isPositiveInteger(k) then
			return false
		end
	end
	return true
end

local function renderSequence(t, reprSettings, indent, depth, shown)
	local tabs = indent:rep(depth)
	local str = "{" .. (reprSettings.pretty and ("\n" .. indent .. tabs) or "")
	for i = 1, #t do
		if i ~= 1 then
			str = str .. (reprSettings.semicolons and ";" or ",") .. (reprSettings.pretty and ("\n" .. indent .. tabs) or " ")
		end
		depth = depth + 1
		str = str .. reprRecursive(t[i], reprSettings, indent, depth, shown)
		depth = depth - 1
	end
	if reprSettings.pretty then
		str = str .. "\n" .. tabs
	end
	str = str .. "}"
	return str
end

local function renderKeyValueTable(t, reprSettings, indent, depth, shown)
	local tabs = indent:rep(depth)
	local str = "{" .. (reprSettings.pretty and ("\n" .. indent .. tabs) or "")
	local keyOrder = {}
	local keyValueStrings = {}
	for k, v in pairs(t) do
		depth = depth + 1
		local kStr = isLuaIdentifier(k) and k or ("[" .. reprRecursive(k, reprSettings, indent, depth, shown) .. "]")
		local vStr = reprRecursive(v, reprSettings, indent, depth, shown)
		table.insert(keyOrder, kStr)
		keyValueStrings[kStr] = vStr
		depth = depth - 1
	end
	if reprSettings.sortKeys then table.sort(keyOrder) end
	local first = true
	for _, kStr in pairs(keyOrder) do
		if not first then
			str = str .. (reprSettings.semicolons and ";" or ",") .. (reprSettings.pretty and ("\n" .. indent .. tabs) or " ")
		end
		str = str .. ("%s = %s"):format(kStr, keyValueStrings[kStr])
		first = false
	end
	if reprSettings.pretty then
		str = str .. "\n" .. tabs
	end
	str = str .. "}"
	return str
end

local function renderTable(t, reprSettings, indent, depth, shown)
	if hasTostringMetamethod(t) then
		return tostring(t)
	elseif shown[t] then
		return "{CYCLIC}"
	end
	shown[t] = true
	local result
	if isSequence(t) then
		result = renderSequence(t, reprSettings, indent, depth, shown)
	else
		result = renderKeyValueTable(t, reprSettings, indent, depth, shown)
	end
	shown[t] = false
	return result
end
 
function reprRecursive(value, reprSettings, indent, depth, shown)
	if value == nil then
		return "nil"
	end
	local valueType = type(value)
	if valueType == "boolean" then
		return tostring(value)
	elseif valueType == "number" then
		return renderNumber(value)
	elseif valueType == "string" then
		return renderString(value)
	elseif valueType == "table" then
		return renderTable(value, reprSettings, indent, depth, shown)
	else
		return "<" .. valueType .. ">"
	end
end

local function repr(value, reprSettings)
	reprSettings = reprSettings or {}
	for setting, settingValue in pairs(defaultSettings) do
		if reprSettings[setting] == nil then
			reprSettings[setting] = defaultSettings[setting]
		end
	end
	
	local indent = (" "):rep(reprSettings.spaces or defaultSettings.spaces)
	if reprSettings.tabs then
		indent = "\t"
	end

	local depth = 0	
	local shown = {} 

	return reprRecursive(value, reprSettings, indent, depth, shown)
end
 
return {
	isLuaIdentifier = isLuaIdentifier,
	repr = repr,
}