initial

using_xpcall.lua

@@ -0,0 +1,175 @@
+local formspec_log = futil and futil.Deque and futil.Deque()
+
+if not formspec_log then
+    -- no deque implementation found
+    local deq = {}
+    deq.size = function(self)
+        return #self
+    end
+    deq.push_front = function(self, v)
+        table.insert(self, v)
+    end
+    deq.pop_back = function(self)
+        local v = self[1]
+        table.remove(self, 1)
+        return v
+    end
+    deq.iterate = function(self)
+        local i = 0
+        return function()
+            i = i + 1
+            local v = self[i]
+            if v then
+                return v
+            end
+        end
+    end
+    deq.__index = deq
+    formspec_log = setmetatable({}, deq)
+end
+
+local LOG_SIZE = 100
+
+-- use deque for logging, pushing oldest log item out
+local function log_add(msg)
+    core.log('error', type(msg) == "string" and msg or dump(msg))
+    formspec_log:push_front(msg)
+    if formspec_log:size() > LOG_SIZE then
+        formspec_log:pop_back()
+    end
+end
+
+
+local function formspec_log_clear()
+    formspec_log:clear()
+end
+
+
+-- passes to xpcall to be able to capture the call stack
+local function error_printer(err)
+    log_add(err)
+    log_add(debug.traceback("----------------------", 2))
+end
+
+
+-- Takes any function and returns a function that takes and returns
+-- same [multiple] values if no error happens. On error, logs it.
+local function safe_wrap(func)
+    local function wrap_f(...)
+        local res = {xpcall(func, error_printer, ...)}
+        if res[1] then
+            -- no error, just return rest of the values
+            return select(2, unpack(res))
+        else
+            -- error was logged by error_printer already
+            local msg = dump(res[2])
+            if msg then
+                log_add(msg)
+            end
+            return nil
+        end
+    end
+    return wrap_f
+end
+
+
+local function formspec_log_show(playername)
+    local log_items = {}
+    for item in formspec_log:iterate() do
+        table.insert(log_items, type(item) == "string" and item or dump(item))
+    end
+    local formspec_template = [[ formspec_version[6] size[16,9] textarea[0.1,0.4;15.8,8.5;log;log;%s] ]]
+    local log_text = core.formspec_escape(table.concat(log_items,'\n'))
+    core.show_formspec(playername, "yl_commons:formspec_log", string.format(formspec_template, log_text))
+end
+
+
+
+core.register_chatcommand(
+    "debug_formspec_log_show",
+    {
+        privs = { server = true },
+        func = function(playername, _params)
+            formspec_log_show(playername)
+            return true
+        end,
+    }
+)
+
+core.register_chatcommand(
+    "debug_formspec_log_clear",
+    {
+        privs = { server = true },
+        func = function(playername, _params)
+            formspec_log_clear(playername)
+            return true
+        end,
+    }
+)
+
+
+--------------------------------------------------------------------------------
+--- Usage example
+
+local function bugged(playername, params)
+    for _=1,tonumber(params) do
+        core.chat_send_all("Hello!")
+    end
+    return true, playername
+end
+
+
+core.register_chatcommand(
+    "bugged",
+    {
+        privs = { },
+        func = function(playername, params)
+            return bugged(playername, params)
+        end,
+    }
+)
+
+
+core.register_chatcommand(
+    "bugged_safe",
+    {
+        privs = { },
+        func = function(playername, params)
+            local status, ret1, ret2 = pcall(bugged, playername, params)
+            -- `status` will be `false` if function call raised an error
+            -- `ret1` will contain the error message on error, or first returned value on no errors
+            -- `ret2` will contain second returned value on no errors
+            -- etc.
+            return status, string.format("%s | %s", ret1, ret2)
+        end,
+    }
+)
+
+
+core.register_chatcommand(
+    "bugged_safe2",
+    {
+        privs = { },
+        func = function(playername, params)
+            -- NOTE: if this does not work, you may need to make sure you're using luajit or newer lua
+            local status, ret1, ret2 = xpcall(bugged, error_printer, playername, params)
+            -- `status` will be `false` if function call raised an error
+            -- `ret1` will contain the error message on error, or first returned value on no errors
+            -- `ret2` will contain second returned value on no errors
+            -- etc.
+            return status, string.format("%s | %s", ret1, ret2)
+        end,
+    }
+)
+
+
+core.register_chatcommand(
+    "bugged_safe3",
+    {
+        privs = { },
+        func = function(playername, params)
+            local safe_bugged = safe_wrap(bugged)
+            return safe_bugged(playername, params)
+        end,
+    }
+)