From 679a5a3bcae1eb55aa4203132a3b1003c1e2c7b3 Mon Sep 17 00:00:00 2001
From: Paul Kulchenko <paul@kulchenko.com>
Date: Fri, 1 Sep 2017 11:23:47 -0700
Subject: [PATCH] Added `metatostring` option to disable `__tostring`
 processing during serialization.

Ref pkulchenko/MobDebug#27, pkulchenko/MobDebug#29.
---
 README.md       | 2 ++
 src/serpent.lua | 8 ++++----
 t/test.lua      | 5 +++++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 890265b..a6e5bbe 100644
--- a/README.md
+++ b/README.md
@@ -74,6 +74,8 @@ Similar to `pcall` and `loadstring` calls, `load` returns status as the first va
 * maxlevel (number) -- specify max level up to which to expand nested tables.
 * maxnum (number) -- specify max number of elements in a table.
 * maxlength (number) -- specify max length for all table elements.
+* metatostring (True/false) -- use `__tostring` metamethod when serializing tables (**v0.29**);
+set to `false` to disable and serialize the table as is, even when `__tostring` is present.
 * numformat (string; "%.17g") -- specify format for numeric values (shortest possible round-trippable double).
 * valignore (table) -- allows to specify a list of values to ignore (as keys).
 * keyallow (table) -- allows to specify the list of keys to be serialized.
diff --git a/src/serpent.lua b/src/serpent.lua
index c5e862b..a5012c4 100644
--- a/src/serpent.lua
+++ b/src/serpent.lua
@@ -1,4 +1,4 @@
-local n, v = "serpent", 0.289 -- (C) 2012-17 Paul Kulchenko; MIT License
+local n, v = "serpent", "0.29" -- (C) 2012-17 Paul Kulchenko; MIT License
 local c, d = "Paul Kulchenko", "Lua serializer and pretty printer"
 local snum = {[tostring(1/0)]='1/0 --[[math.huge]]',[tostring(-1/0)]='-1/0 --[[-math.huge]]',[tostring(0/0)]='0/0'}
 local badtype = {thread = true, userdata = true, cdata = true}
@@ -15,7 +15,7 @@ local function s(t, opts)
   local name, indent, fatal, maxnum = opts.name, opts.indent, opts.fatal, opts.maxnum
   local sparse, custom, huge = opts.sparse, opts.custom, not opts.nohuge
   local space, maxl = (opts.compact and '' or ' '), (opts.maxlevel or math.huge)
-  local maxlen = tonumber(opts.maxlength)
+  local maxlen, metatostring = tonumber(opts.maxlength), opts.metatostring
   local iname, comm = '_'..(name or ''), opts.comment and (tonumber(opts.comment) or math.huge)
   local numformat = opts.numformat or "%.17g"
   local seen, sref, syms, symn = {}, {'local '..iname..'={}'}, {}, 0
@@ -53,9 +53,9 @@ local function s(t, opts)
     if type(mt) == 'table' then
       local to, tr = pcall(function() return mt.__tostring(t) end)
       local so, sr = pcall(function() return mt.__serialize(t) end)
-      if (to or so) then -- knows how to serialize itself
+      if (opts.metatostring ~= false and to or so) then -- knows how to serialize itself
         seen[t] = insref or spath
-        if so then t = sr else t = tostring(t) end
+        t = so and sr or tr
         ttype = type(t)
       end -- new value falls through to be serialized
     end
diff --git a/t/test.lua b/t/test.lua
index 532515e..5ba35a3 100644
--- a/t/test.lua
+++ b/t/test.lua
@@ -143,6 +143,11 @@ do
   assert(_a.y == 12, "metatable with __tostring and __index 1: failed")
   assert(_a[1] == 'a', "metatable with __tostring and __index 2: failed")
   assert(_a.x == 1, "metatable with __tostring and __index 3: failed")
+
+  -- check that __tostring is not used when disabled
+  local _a = assert(loadstring(serpent.dump(a, {sparse = false, nocode = true, metatostring = false})))()
+  assert(_a[1] == 'a', "metatable with disabled __tostring and __index 1: failed")
+  assert(_a[2] == 'b', "metatable with disabled __tostring and __index 2: failed")
 end
 
 -- test circular reference in self-reference section