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This metamodule provides function callAssert, which simplifies error checking by throwing an error if a given function returns nil or false. This is similar to the built-in function assert, but unlike it, callAssert itself calls the function, whose return value is to be checked. This allows it to include the function name and argument values in the error message.
Usage
local callAssert = require('Module:CallAssert') local result1, result2, etc = callAssert(func, 'funcName', ...)
callAssert
calls func(...)
and checks if the first returned value evaluates to true. If it does, then it returns all the returned values. If not, it throws an error with a message in the form 'funcName(argument_values) failed'
.
local function pack(...)
return {...}, select('#', ...)
end
local function mapArray(func, array, count)
local result = {}
for i = 1, count or #array do
result[i] = func(array[i])
end
return result
end
local function quote(value)
if type(value) == 'string' then
return (string.gsub(string.format('%q', value), '\\\n', '\\n')) -- Outer parentheses remove second value returned by gsub
end
local str = tostring(value)
if type(value) == 'table' and str ~= 'table' then
return '{' .. str .. '}'
end
return str
end
local function callAssert(func, funcName, ...)
local result, resultCount = pack(func(...))
if not result[1] then
local args, argsCount = pack(...)
args = mapArray(quote, args, argsCount)
local message = mw.ustring.format(
'%s(%s) failed',
funcName,
table.concat(args, ', ')
)
error(message, 2)
end
return unpack(result, 1, resultCount)
end
return callAssert