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|
--- Useful error stack objects
--
-- Many NSE library functions return a boolean status and an optional error
-- message. The Oops library consists of several simple functions to accumulate
-- these errors and pass them up the stack, resulting in a useful and verbose
-- error message when debugging.
--
-- @author Daniel Miller
-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
-- @class module
-- @name oops
local require = require
local setmetatable = setmetatable
local _ENV = require "strict" {}
local nmap = require "nmap"
local debugging = nmap.debugging
local verbosity = nmap.verbosity
local table = require "table"
local concat = table.concat
local insert = table.insert
local Oops = {
new = function (self, message)
local o = {message}
setmetatable(o, self)
self.__index = self
return o
end,
push = function (self, message)
insert(self, 1, message)
end,
__tostring = function (self)
local banner = "The script encountered an error"
local sep = ":\n- "
if debugging() > 0 then
-- Print full error trace
return banner .. sep .. concat(self, sep)
end
if verbosity() > 0 then
-- Show just the top error
return banner .. ": " .. self[1]
end
-- By default, no string output shown.
return ""
end,
}
--- Add an error message to a stack of errors
--
-- @param message The error message to add to the stack.
-- @param previous (Optional) Any error reported by other functions that failed.
-- @return An Oops object representing the error stack.
err = function (message, previous)
local result
if previous then
if previous.push then
result = previous
else
result = Oops:new(previous)
end
result:push(message)
elseif message.push then
result = message
else
result = Oops:new(message)
end
return result
end
local err = err
--- Report an error or return a good value
--
-- If the status is true, just return the message. If it's false, return the
-- message as an Oops object. This can be easily used as the final return value
-- of a script.
-- @param status The return status of the script.
-- @param message The output of the script, or an error message if status is false.
-- @return The message if status is true, or an error message if it is false.
output = function (status, message)
if status then
return message
else
return err(message)
end
end
local output = output
--- Report a status and error or return values
--
-- This is intended to wrap a function that returns a status and either an
-- error or some value. If the status is false, the message is added to the
-- stack of errors. Instead of this code:
--
-- <code>
-- local status, value_or_error, value = somefunction(args)
-- if not status then
-- return status, "somefunction failed for some reason"
-- end
-- </code>
--
-- with this instead:
--
-- <code>
-- local status, value_or_error, value = oops.raise("somefunction failed", somefunction(args))
-- if not status then
-- return status, value_or_error
-- end
-- </code>
--
-- but instead of just the one error, you get a stack of errors from
-- <code>somefunction</code> with your own message at the top.
--
-- @param message The error message to report if status is false.
-- @param status The first return value of the function. Treated as boolean, but returned unmodified.
-- @param previous The second return value of the function, or error.
-- @return The same status that was input.
-- @return The rest of the return values, but on error, the message will be added to the stack.
raise = function (message, status, previous, ...)
local r = previous
if not status then
r = err(message, previous)
end
return status, r, ...
end
return _ENV
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