Added serialization of metatables using __tostring (when present).

README.md

@@ -128,6 +128,10 @@ See LICENSE file.
 
 ## History
 
+Nov 16 2012 v0.19
+  - Fixed an issue with serializing shared functions as keys.
+  - Added serialization of metatables using __tostring (when present).
+
 Sep 13 2012 v0.18
   - Fixed an issue with serializing data structures with circular references that require emitting temporary variables.
   - Fixed an issue with serializing keys pointing to shared references.

src/serpent.lua

@@ -1,4 +1,4 @@
-local n, v = "serpent", 0.18 -- (C) 2012 Paul Kulchenko; MIT License
+local n, v = "serpent", 0.19 -- (C) 2012 Paul Kulchenko; MIT License
 local c, d = "Paul Kulchenko", "Serializer and pretty printer of Lua data types"
 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}
@@ -57,6 +57,8 @@ local function s(t, opts)
     elseif ttype == "table" then
       if level >= maxl then return tag..'{}'..comment('max', level) end
       seen[t] = insref or spath -- set path to use as reference
+      if getmetatable(t) and getmetatable(t).__tostring
+        then return tag..safestr(tostring(t))..comment("meta",l) end
       if next(t) == nil then return tag..'{}'..comment(t, level) end -- table empty
       local maxn, o, out = #t, {}, {}
       for key = 1, maxn do table.insert(o, key) end

t/test.lua

@@ -96,7 +96,6 @@ do
   local tbl = {'tbl'}
   a[3] = {[{}] = {happy = tbl}, sad = tbl}
 
-  print(serpent.dump(a, {sparse = false, nocode = true}))
   assert(loadstring(serpent.dump(a, {sparse = false, nocode = true})),
     "table as key with circular/shared reference: failed")
 end
@@ -108,9 +107,19 @@ do
   a.a[function1]=function() end
   a.b=a.a[function1]
 
-  print(serpent.dump(a, {sparse = false, nocode = true}))
   assert(loadstring(serpent.dump(a, {sparse = false, nocode = true})),
     "functions as shared references while processing shared refs: failed")
 end
 
+-- test serialization of metatable with __tostring
+do
+  local mt = {}
+  mt.__tostring = function(t) return 'table with ' .. #t .. ' entries' end
+  local a = {'a', 'b'}
+  setmetatable(a, mt)
+
+  assert(loadstring(serpent.dump(a, {sparse = false, nocode = true, comment = true})),
+    "metatable with __tostring serialized with a comment: failed")
+end
+
 print("All tests passed.")