luci-base: update coxpcall() implementation, fix runtime error reporting

Sync our coxpcall() implementation to the newest upstream version in order to
get access to the inner backtrace information and propagate these traces to
the browser in luci.dispatcher.dispatch().

This should make tracking down runtime errors much easier.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/luasrc/dispatcher.lua

@@ -358,7 +358,7 @@ function dispatch(request)
 			elseif key == "REQUEST_URI" then
 				return build_url(unpack(ctx.requestpath))
 			elseif key == "FULL_REQUEST_URI" then
-				local url = { http.getenv("SCRIPT_NAME") or "" , http.getenv("PATH_INFO") }
+				local url = { http.getenv("SCRIPT_NAME") or "", http.getenv("PATH_INFO") }
 				local query = http.getenv("QUERY_STRING")
 				if query and #query > 0 then
 					url[#url+1] = "?"
@@ -507,10 +507,11 @@ function dispatch(request)
 		else
 			ok, err = util.copcall(target, unpack(args))
 		end
-		assert(ok,
+		if not ok then
-		       "Failed to execute " .. (type(c.target) == "function" and "function" or c.target.type or "unknown") ..
+			error500("Failed to execute " .. (type(c.target) == "function" and "function" or c.target.type or "unknown") ..
-		       " dispatcher target for entry '/" .. table.concat(request, "/") .. "'.\n" ..
+			         " dispatcher target for entry '/" .. table.concat(request, "/") .. "'.\n" ..
-		       "The called action terminated with an exception:\n" .. tostring(err or "(unknown)"))
+			         "The called action terminated with an exception:\n" .. tostring(err or "(unknown)"))
+		end
 	else
 		local root = node()
 		if not root or not root.target then

modules/luci-base/luasrc/util.lua

@@ -100,6 +100,8 @@ end
 -- Scope manipulation routines
 --
 
+coxpt = setmetatable({}, { __mode = "kv" })
+
 local tl_meta = {
 	__mode = "k",
 
@@ -697,73 +699,69 @@ function checklib(fullpathexe, wantedlib)
 	return false
 end
 
+-------------------------------------------------------------------------------
+-- Coroutine safe xpcall and pcall versions
 --
--- Coroutine safe xpcall and pcall versions modified for Luci
+-- Encapsulates the protected calls with a coroutine based loop, so errors can
--- original version:
+-- be dealed without the usual Lua 5.x pcall/xpcall issues with coroutines
--- coxpcall 1.13 - Copyright 2005 - Kepler Project (www.keplerproject.org)
+-- yielding inside the call to pcall or xpcall.
 --
--- Copyright © 2005 Kepler Project.
+-- Authors: Roberto Ierusalimschy and Andre Carregal
--- Permission is hereby granted, free of charge, to any person obtaining a
+-- Contributors: Thomas Harning Jr., Ignacio Burgueño, Fabio Mascarenhas
--- copy of this software and associated documentation files (the "Software"),
--- to deal in the Software without restriction, including without limitation
--- the rights to use, copy, modify, merge, publish, distribute, sublicense,
--- and/or sell copies of the Software, and to permit persons to whom the
--- Software is furnished to do so, subject to the following conditions:
 --
--- The above copyright notice and this permission notice shall be
+-- Copyright 2005 - Kepler Project
--- included in all copies or substantial portions of the Software.
 --
--- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+-- $Id: coxpcall.lua,v 1.13 2008/05/19 19:20:02 mascarenhas Exp $
--- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+-------------------------------------------------------------------------------
--- OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
--- IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
--- DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
--- TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
--- OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-local performResume, handleReturnValue
+-------------------------------------------------------------------------------
-local oldpcall, oldxpcall = pcall, xpcall
+-- Implements xpcall with coroutines
-coxpt = {}
+-------------------------------------------------------------------------------
-setmetatable(coxpt, {__mode = "kv"})
+local coromap = setmetatable({}, { __mode = "k" })
 
--- Identity function for copcall
+local function handleReturnValue(err, co, status, ...)
-local function copcall_id(trace, ...)
-  return ...
-end
-
---				values of either the function or the error handler
-function coxpcall(f, err, ...)
-	local res, co = oldpcall(coroutine.create, f)
-	if not res then
-		local params = {...}
-		local newf = function() return f(unpack(params)) end
-		co = coroutine.create(newf)
-	end
-	local c = coroutine.running()
-	coxpt[co] = coxpt[c] or c or 0
-
-	return performResume(err, co, ...)
-end
-
---				values of the function or the error object
-function copcall(f, ...)
-	return coxpcall(f, copcall_id, ...)
-end
-
--- Handle return value of protected call
-function handleReturnValue(err, co, status, ...)
 	if not status then
 		return false, err(debug.traceback(co, (...)), ...)
 	end
-
+	if coroutine.status(co) == 'suspended' then
-	if coroutine.status(co) ~= 'suspended' then
+		return performResume(err, co, coroutine.yield(...))
+	else
 		return true, ...
 	end
-
-	return performResume(err, co, coroutine.yield(...))
 end
 
--- Resume execution of protected function call
 function performResume(err, co, ...)
 	return handleReturnValue(err, co, coroutine.resume(co, ...))
 end
+
+local function id(trace, ...)
+	return trace
+end
+
+function coxpcall(f, err, ...)
+	local current = coroutine.running()
+	if not current then
+		if err == id then
+			return pcall(f, ...)
+		else
+			if select("#", ...) > 0 then
+				local oldf, params = f, { ... }
+				f = function() return oldf(unpack(params)) end
+			end
+			return xpcall(f, err)
+		end
+	else
+		local res, co = pcall(coroutine.create, f)
+		if not res then
+			local newf = function(...) return f(...) end
+			co = coroutine.create(newf)
+		end
+		coromap[co] = current
+		coxpt[co] = coxpt[current] or current or 0
+		return performResume(err, co, ...)
+	end
+end
+
+function copcall(f, ...)
+	return coxpcall(f, id, ...)
+end