util.array: Fix equality metamethod in Lua 5.3
Lua 5.2 only used the __eq metamethod if both operands have the same
__eq, but Lua 5.3 will pick one from either operands that has one as
long as both are tables.
This results in array() == {} and all sorts of odd behavior, including
array() == util.json.null.
<MattJ> I think [array() == {}] should have the same semantics as {} == {}
--- a/util/array.lua Wed Jan 15 21:14:06 2020 +0100
+++ b/util/array.lua Wed Jan 15 21:08:01 2020 +0100
@@ -10,6 +10,7 @@
= table.insert, table.sort, table.remove, table.concat;
local setmetatable = setmetatable;
+local getmetatable = getmetatable;
local math_random = math.random;
local math_floor = math.floor;
local pairs, ipairs = pairs, ipairs;
@@ -40,6 +41,10 @@
end
function array_mt.__eq(a, b)
+ if getmetatable(a) ~= array_mt or getmetatable(b) ~= array_mt then
+ -- Lua 5.3+ calls this if both operands are tables, even if metatables differ
+ return false;
+ end
if #a == #b then
for i = 1, #a do
if a[i] ~= b[i] then