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local type = type
local debug_traceback = type(debug) == "table" and type(debug.traceback) == "function" and debug.traceback
local function traceback(x)
-- Attempt to detect error() and error("xyz", 0).
-- This probably means they're erroring the program intentionally and so we
-- shouldn't display anything.
if x == nil or (type(x) == "string" and not x:find(":%d+:")) then
return x
end
if debug_traceback then
-- The parens are important, as they prevent a tail call occuring, meaning
-- the stack level is preserved. This ensures the code behaves identically
-- on LuaJ and PUC Lua.
return (debug_traceback(tostring(x), 2))
else
local level = 3
local out = { tostring(x), "stack traceback:" }
while true do
local _, msg = pcall(error, "", level)
if msg == "" then break end
out[#out + 1] = " " .. msg
level = level + 1
end
return table.concat(out, "\n")
end
end
local function trim_traceback(target, marker)
local ttarget, tmarker = {}, {}
for line in target:gmatch("([^\n]*)\n?") do ttarget[#ttarget + 1] = line end
for line in marker:gmatch("([^\n]*)\n?") do tmarker[#tmarker + 1] = line end
-- Trim identical suffixes
local t_len, m_len = #ttarget, #tmarker
while t_len >= 3 and ttarget[t_len] == tmarker[m_len] do
table.remove(ttarget, t_len)
t_len, m_len = t_len - 1, m_len - 1
end
-- Trim elements from this file and xpcall invocations
while t_len >= 1 and ttarget[t_len]:find("^\tstack_trace%.lua:%d+:") or
ttarget[t_len] == "\t[C]: in function 'xpcall'" or ttarget[t_len] == " xpcall: " do
table.remove(ttarget, t_len)
t_len = t_len - 1
end
return ttarget
end
--- Run a function with
local function xpcall_with(fn)
-- So this is rather grim: we need to get the full traceback and current one and remove
-- the common prefix
local trace
local res = table.pack(xpcall(fn, traceback)) if not res[1] then trace = traceback("trace.lua:1:") end
local ok, err = res[1], res[2]
if not ok and err ~= nil then
trace = trim_traceback(err, trace)
-- Find the position where the stack traceback actually starts
local trace_starts
for i = #trace, 1, -1 do
if trace[i] == "stack traceback:" then trace_starts = i; break end
end
-- If this traceback is more than 15 elements long, keep the first 9, last 5
-- and put an ellipsis between the rest
local max = 15
if trace_starts and #trace - trace_starts > max then
local keep_starts = trace_starts + 10
for i = #trace - trace_starts - max, 0, -1 do table.remove(trace, keep_starts + i) end
table.insert(trace, keep_starts, " ...")
end
return false, table.concat(trace, "\n")
end
return table.unpack(res, 1, res.n)
end
_ENV.traceback = traceback
_ENV.trim_traceback = trim_traceback
_ENV.xpcall_with = xpcall_with
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