use iodata for json serialization

lib/elixir/lib/calendar/duration.ex

@@ -532,7 +532,7 @@ defmodule Duration do
       sign,
       Integer.to_string(second),
       ?.,
-      ms |> Integer.to_string() |> String.pad_leading(6, "0") |> binary_part(0, p)
+      Calendar.ISO.microseconds_to_iodata(ms, p)
     ]
   end
 

lib/elixir/lib/json.ex

@@ -150,9 +150,93 @@ defimpl JSON.Encoder, for: Map do
   end
 end
 
-defimpl JSON.Encoder, for: [Date, Time, NaiveDateTime, DateTime, Duration] do
+defimpl JSON.Encoder, for: Duration do
   def encode(value, _encoder) do
-    [?", @for.to_iso8601(value), ?"]
+    [?", Duration.to_iso8601(value), ?"]
+  end
+end
+
+defimpl JSON.Encoder, for: Date do
+  def encode(%{calendar: Calendar.ISO} = date, _encoder) do
+    %{year: year, month: month, day: day} = date
+    [?", Calendar.ISO.date_to_iodata(year, month, day), ?"]
+  end
+
+  def encode(value, _encoder) do
+    [?", Date.to_iso8601(value), ?"]
+  end
+end
+
+defimpl JSON.Encoder, for: Time do
+  def encode(%{calendar: Calendar.ISO} = time, _encoder) do
+    %{
+      hour: hour,
+      minute: minute,
+      second: second,
+      microsecond: microsecond
+    } = time
+
+    [?", Calendar.ISO.time_to_iodata(hour, minute, second, microsecond), ?"]
+  end
+
+  def encode(value, _encoder) do
+    [?", Time.to_iso8601(value), ?"]
+  end
+end
+
+defimpl JSON.Encoder, for: NaiveDateTime do
+  def encode(%{calendar: Calendar.ISO} = naive_datetime, _encoder) do
+    %{
+      year: year,
+      month: month,
+      day: day,
+      hour: hour,
+      minute: minute,
+      second: second,
+      microsecond: microsecond
+    } = naive_datetime
+
+    [
+      ?",
+      Calendar.ISO.date_to_iodata(year, month, day),
+      ?T,
+      Calendar.ISO.time_to_iodata(hour, minute, second, microsecond),
+      ?"
+    ]
+  end
+
+  def encode(value, _encoder) do
+    [?", NaiveDateTime.to_iso8601(value), ?"]
+  end
+end
+
+defimpl JSON.Encoder, for: DateTime do
+  def encode(%{calendar: Calendar.ISO} = datetime, _encoder) do
+    %{
+      year: year,
+      month: month,
+      day: day,
+      hour: hour,
+      minute: minute,
+      second: second,
+      microsecond: microsecond,
+      time_zone: time_zone,
+      utc_offset: utc_offset,
+      std_offset: std_offset
+    } = datetime
+
+    [
+      ?",
+      Calendar.ISO.date_to_iodata(year, month, day),
+      ?T,
+      Calendar.ISO.time_to_iodata(hour, minute, second, microsecond),
+      Calendar.ISO.offset_to_iodata(utc_offset, std_offset, time_zone, :extended),
+      ?"
+    ]
+  end
+
+  def encode(value, _encoder) do
+    [?", DateTime.to_iso8601(value), ?"]
   end
 end
 

lib/elixir/test/elixir/json_test.exs

@@ -99,6 +99,18 @@ defmodule JSONTest do
     list = JSON.encode_to_iodata!([1, 1.0, "one", %{1 => 2, 3.0 => 4.0, key: :bar}])
     assert is_list(list)
     assert IO.iodata_to_binary(list) == "[1,1.0,\"one\",{\"1\":2,\"3.0\":4.0,\"key\":\"bar\"}]"
+
+    list =
+      JSON.encode_to_iodata!([
+        ~T[12:34:56.78],
+        ~D[2024-12-31],
+        ~N[2010-04-17 14:00:00.123],
+        ~U[2010-04-17 14:00:00.123Z],
+        Duration.new!(month: 2, hour: 3)
+      ])
+
+    assert IO.iodata_to_binary(list) ==
+             ~s'["12:34:56.78","2024-12-31","2010-04-17T14:00:00.123","2010-04-17T14:00:00.123Z","P2MT3H"]'
   end
 
   test "deprecated" do