dump_table: Sort keys before printing

This commit is contained in:
jakobrs
2021-08-08 11:19:40 +02:00
committed by George Kiagiadakis
parent 86bfdbea13
commit 92d99f4a75

View File

@@ -77,7 +77,56 @@ local function dump_table(t, indent)
indent_str = indent_str .. "\t"
end
local kvpairs = {}
for k, v in pairs(t) do
table.insert(kvpairs, { k, v })
end
table.sort(kvpairs, function (lhs, rhs)
local left_key, right_key = lhs[1], rhs[1]
-- If the types are different, we sort by the type
-- in alphabetical order. This means that numbers
-- come before before strings, etc
if type(left_key) ~= type(right_key) then
return type(left_key) < type(right_key)
end
local key_type = type(left_key)
-- Only numbers and strings have a well-defined order
-- that's guaranteed to fulfill the requirements of
-- table.sort (strict weak order)
if key_type == "number" or key_type == "string" then
return left_key < right_key
end
-- At this point, we have no good way to order the objects.
-- We can't just do `left_key < right_key`, because this may fail
-- if there's no `__lt` metamethod, and even if there is one,
-- it might not be a strict weak order. (The Lua reference does
-- not say what happens if the order is not strict weak, so it's
-- undefined behaviour)
-- That said, it's always mathematically "permitted" to return `false`,
-- in which case, since both x < y and y < x are false, the elements
-- are considered "equivalent" and may appear in any order in relation
-- to each other. The elements are still sorted in relation to the
-- *other* keys.
return false
-- To be a strict weak order, if x and y are equivalent, and y and z
-- are equivalent, then x and z must be equivalent too. Otherwise the
-- ordering is only a strict *partial* order.
-- Note that the Lua 5.3 reference states that the order merely has to
-- be a strict *partial* order, but since all weak orders are partial
-- orders, this is not a problem.
end)
for _, pair in ipairs(kvpairs) do
local k, v = table.unpack(pair)
if (type(v) == "table") then
print (indent_str .. tostring(k) .. ": ")
dump_table(v, indent + 1)