factor out dump() function, handle reference loops

frontend/dbg.lua

@@ -1,4 +1,4 @@
-local DocSettings = require("docsettings") -- for dump method
+local dump = require("dump")
 local isAndroid, android = pcall(require, "android")
 
 local Dbg = {
@@ -12,7 +12,7 @@ local function LvDEBUG(lv, ...)
     local line = ""
     for i,v in ipairs({...}) do
         if type(v) == "table" then
-            line = line .. " " .. DocSettings:dump(v, lv)
+            line = line .. " " .. dump(v, lv)
         else
             line = line .. " " .. tostring(v)
         end

frontend/docsettings.lua

@@ -1,5 +1,6 @@
 local lfs = require("libs/libkoreader-lfs")
 local DocSettings = {}
+local dump = require("dump")
 
 function DocSettings:getHistoryPath(fullpath)
     return "./history/[" .. fullpath:gsub("(.*/)([^/]+)","%1] %2"):gsub("/","#") .. ".lua"
@@ -71,49 +72,6 @@ function DocSettings:delSetting(key)
     self.data[key] = nil
 end
 
-function DocSettings:dump(data, max_lv)
-    local out = {}
-    self:_serialize(data, out, 0, max_lv)
-    return table.concat(out)
-end
-
--- simple serialization function, won't do uservalues, functions, loops
-function DocSettings:_serialize(what, outt, indent, max_lv)
-    if not max_lv then
-        max_lv = math.huge
-    end
-
-    if indent > max_lv then
-        return
-    end
-
-    if type(what) == "table" then
-        local didrun = false
-        table.insert(outt, "{")
-        for k, v in pairs(what) do
-            if didrun then
-                table.insert(outt, ",")
-            end
-            table.insert(outt, "\n")
-            table.insert(outt, string.rep("\t", indent+1))
-            table.insert(outt, "[")
-            self:_serialize(k, outt, indent+1, max_lv)
-            table.insert(outt, "] = ")
-            self:_serialize(v, outt, indent+1, max_lv)
-            didrun = true
-        end
-        if didrun then
-            table.insert(outt, "\n")
-            table.insert(outt, string.rep("\t", indent))
-        end
-        table.insert(outt, "}")
-    elseif type(what) == "string" then
-        table.insert(outt, string.format("%q", what))
-    elseif type(what) == "number" or type(what) == "boolean" then
-        table.insert(outt, tostring(what))
-    end
-end
-
 function DocSettings:flush()
     -- write serialized version of the data table into
     --  i) history directory in root directory of koreader
@@ -130,13 +88,12 @@ function DocSettings:flush()
         pcall(table.insert, serials, io.open(self.sidecar_file, "w"))
     end
     os.setlocale('C', 'numeric')
-    local out = {"-- we can read Lua syntax here!\nreturn "}
-    self:_serialize(self.data, out, 0)
-    table.insert(out, "\n")
-    local s_out = table.concat(out)
+    local s_out = dump(self.data)
     for _, f_out in ipairs(serials) do
         if f_out ~= nil then
+            f_out:write("-- we can read Lua syntax here!\nreturn ")
             f_out:write(s_out)
+            f_out:write("\n")
             f_out:close()
         end
     end

frontend/dump.lua

@@ -0,0 +1,69 @@
+--[[
+simple serialization function, won't do uservalues, functions, loops
+]]
+
+local insert = table.insert
+
+local function _serialize(what, outt, indent, max_lv, history)
+    if not max_lv then
+        max_lv = math.huge
+    end
+
+    if indent > max_lv then
+        return
+    end
+
+    history = history or {}
+    for up, item in ipairs(history) do
+        if item == what then
+            insert(outt, "nil --[[ LOOP:\n")
+            insert(outt, string.rep("\t", indent - up))
+            insert(outt, "^------- ]]")
+            return
+        end
+    end
+
+    if type(what) == "table" then
+        local new_history = { what, unpack(history) }
+        local didrun = false
+        insert(outt, "{")
+        for k, v in pairs(what) do
+            if didrun then
+                insert(outt, ",")
+            end
+            insert(outt, "\n")
+            insert(outt, string.rep("\t", indent+1))
+            insert(outt, "[")
+            _serialize(k, outt, indent+1, max_lv, new_history)
+            insert(outt, "] = ")
+            _serialize(v, outt, indent+1, max_lv, new_history)
+            didrun = true
+        end
+        if didrun then
+            insert(outt, "\n")
+            insert(outt, string.rep("\t", indent))
+        end
+        insert(outt, "}")
+    elseif type(what) == "string" then
+        insert(outt, string.format("%q", what))
+    elseif type(what) == "number" or type(what) == "boolean" then
+        insert(outt, tostring(what))
+    elseif type(what) == "function" then
+        insert(outt, "nil --[[ FUNCTION ]]")
+    elseif type(what) == "nil" then
+        insert(outt, "nil")
+    end
+end
+
+--[[
+Serializes whatever is in "data" to a string that is parseable by Lua
+
+You can optionally specify a maximum recursion depth in "max_lv"
+--]]
+local function dump(data, max_lv)
+    local out = {}
+    _serialize(data, out, 0, max_lv)
+    return table.concat(out)
+end
+
+return dump