neiam /apollos_crib

It's Apollo's Crib

JSON: keep the key order Poison wrote

6696166 · Gabriel Morell · 2026-10-23 13:11

8 files +27 -4

Message

{commit_body(@commit)}

modified apps/room_sanctum/lib/room_sanctum/json.ex

+12 −2

@@ -23,7 +23,8 @@ defmodule RoomSanctum.JSON do

23	23
24	24	@doc """
25	25	`term` with everything Jason would refuse made into what Poison wrote
26		− for it. Dates and times are left alone: both write them as ISO 8601.
	26	+ for it, and every map made a `Jason.OrderedObject` in the key order
	27	+ Poison wrote. Dates and times are left alone: both write them as ISO 8601.
27	28	"""
28	29	def normalize(%struct{} = value) when struct in [Date, Time, NaiveDateTime, DateTime], do: value
29	30	def normalize(%Jason.Fragment{} = value), do: value

@@ -32,7 +33,16 @@ defmodule RoomSanctum.JSON do

32	33	def normalize(%Range{} = value), do: Enum.to_list(value)
33	34	def normalize(%MapSet{} = value), do: value \|> MapSet.to_list() \|> normalize()
34	35	def normalize(%_{} = value), do: value \|> Map.from_struct() \|> normalize()
35		− def normalize(value) when is_map(value), do: Map.new(value, fn {k, v} -> {k, normalize(v)} end)
	36	+ # Poison wrote an object's keys in the reverse of the map's own order (it
	37	+ # folds over `Map.keys/1`, prepending), and Jason writes them in that order.
	38	+ # A client that reads a board in the order it arrived -- the Android app
	39	+ # lays its cards out that way -- would see them flip, so the order Poison
	40	+ # wrote is kept.
	41	+ def normalize(value) when is_map(value) do
	42	+ values = :lists.foldl(&[{&1, normalize(Map.fetch!(value, &1))} \| &2], [], Map.keys(value))
	43	+ %Jason.OrderedObject{values: values}
	44	+ end
	45	+
36	46	def normalize(value) when is_list(value), do: Enum.map(value, &normalize/1)
37	47	def normalize(value) when is_tuple(value), do: value \|> Tuple.to_list() \|> normalize()
38	48	def normalize(value), do: value

modified apps/room_sanctum/test/room_sanctum/json_test.exs

+15 −2

@@ -30,12 +30,25 @@ defmodule RoomSanctum.JSONTest do

30	30	end
31	31
32	32	test "ranges and sets become lists, a URI its string" do
33		− assert JSON.encode!(%{r: 1..3, u: URI.parse("https://example.com/x")}) ==
34		− ~s({"r":[1,2,3],"u":"https://example.com/x"})
	33	+ # String keys: a small map orders them, so the order written is fixed.
	34	+ assert JSON.encode!(%{"r" => 1..3, "u" => URI.parse("https://example.com/x")}) ==
	35	+ ~s({"u":"https://example.com/x","r":[1,2,3]})
35	36
36	37	assert JSON.encode!(MapSet.new([{1, 2}])) == ~s([[1,2]])
37	38	end
38	39
	40	+ test "an object's keys come out in the order Poison wrote them" do
	41	+ # The reverse of the map's own order. The Android app lays a board's
	42	+ # cards out in the order the keys arrive, so this is what it shows.
	43	+ board = %{
	44	+ "ephem-1" => %{"data" => [1], "query" => %{"name" => "Sky"}},
	45	+ "gtfs-2" => [%{"a" => 1, "b" => 2}]
	46	+ }
	47	+
	48	+ assert JSON.encode!(board) ==
	49	+ ~s({"gtfs-2":[{"b":2,"a":1}],"ephem-1":{"query":{"name":"Sky"},"data":[1]}})
	50	+ end
	51	+
39	52	test "pretty printing still works" do
40	53	assert JSON.encode!(%{a: 1}, pretty: true) == ~s({\n "a": 1\n})
41	54	end

Parents: 819251f