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.

local defaultSettings = {
	pretty = false;
	tabs = true;
	semicolons = false;
	spaces = 4;
	sortKeys = true;
}
 
-- 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 reprRecursive(value, reprSettings, indent, depth, shown)
	if type(value) == "string" then
		return (("%q"):format(value):gsub("\\\n", "\\n"))
	elseif type(value) == "number" then
		if value == math.huge then return "math.huge" end
		if value == -math.huge then return "-math.huge" end
		return tostring(tonumber(value))
	elseif type(value) == "boolean" then
		return tostring(value)
	elseif type(value) == "nil" then
		return "nil"
	elseif type(value) == "table" and getmetatable(value) and type(getmetatable(value).__tostring) == "function" then
		return tostring(getmetatable(value).__tostring(value))
	elseif type(value) == "table" then
		if shown[value] then return "{CYCLIC}" end
		shown[value] = true
		local tabs = indent:rep(depth)
		local str = "{" .. (reprSettings.pretty and ("\n" .. indent .. tabs) or "")
		local isArray = true
		for k in pairs(value) do
			if type(k) ~= "number" or k < 1 or k == math.huge or k ~= math.floor(k) then
				isArray = false
				break
			end
		end
		if isArray then
			for i = 1, #value 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(value[i], reprSettings, indent, depth, shown)
				depth = depth - 1
			end
		else
			local keyOrder = {}
			local keyValueStrings = {}
			for k, v in pairs(value) 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
		end
		shown[value] = false
		if reprSettings.pretty then
			str = str .. "\n" .. tabs
		end
		str = str .. "}"
		return str
	else
		return "<" .. type(value) .. ">"
	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,
}