From 70556ccea5b33ffcbb62eb1dc7288b287de28438 Mon Sep 17 00:00:00 2001
From: rxi <rxi@users.noreply.github.com>
Date: Sun, 30 Aug 2015 19:08:50 +0100
Subject: [PATCH] Added checking for sparseness and mixed key types when
 encoding array

---
 README.md |  2 +-
 json.lua  | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 03482b4..f814d0a 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ A lightweight JSON library for Lua
 * Implemented in pure Lua: works with 5.1, 5.2, 5.3 and JIT
 * Fast: generally outperforms other pure Lua JSON implementations
   ([benchmark scripts](bench/))
-* Tiny: around 280sloc, 8.5kb
+* Tiny: around 290sloc, 9kb
 * Proper error messages, *eg:* `expected '}' or ',' at line 203 col 30`
 
 
diff --git a/json.lua b/json.lua
index f04724b..205dfb4 100644
--- a/json.lua
+++ b/json.lua
@@ -51,7 +51,19 @@ local function encode_table(val, stack)
   stack[val] = true
 
   if val[1] ~= nil then
-    -- Treat as an array
+    -- Treat as array -- check keys are valid and it is not sparse
+    local n = 0
+    for k in pairs(val) do
+      local t = type(k)
+      if t ~= "number" then
+        error("unexpected key of type '" .. t .. "' in array")
+      end
+      n = n + 1
+    end
+    if n ~= #val then
+      error("unexpected sparse array")
+    end
+    -- Encode
     for i, v in ipairs(val) do
       table.insert(res, encode(v, stack))
     end
@@ -63,7 +75,7 @@ local function encode_table(val, stack)
     for k, v in pairs(val) do
       local t = type(k)
       if t ~= "string" then
-        error("expected key of type 'string', got '" .. t .. "'")
+        error("unexpected key of type '" .. t .. "' in object")
       end
       table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
     end