Also encode Duration to JSON

Author: josevalim

lib/elixir/lib/json.ex

@@ -150,7 +150,7 @@ defimpl JSON.Encoder, for: Map do
   end
 end
 
-defimpl JSON.Encoder, for: [Date, Time, NaiveDateTime, DateTime] do
+defimpl JSON.Encoder, for: [Date, Time, NaiveDateTime, DateTime, Duration] do
   def encode(value, _encoder) do
     [?", @for.to_iso8601(value), ?"]
   end

lib/elixir/test/elixir/json_test.exs

@@ -52,6 +52,7 @@ defmodule JSONTest do
       assert JSON.encode!(~T[14:00:00.123]) == "\"14:00:00.123\""
       assert JSON.encode!(~N[2010-04-17 14:00:00.123]) == "\"2010-04-17T14:00:00.123\""
       assert JSON.encode!(~U[2010-04-17 14:00:00.123Z]) == "\"2010-04-17T14:00:00.123Z\""
+      assert JSON.encode!(Duration.new!(month: 2, hour: 3)) == "\"P2MT3H\""
     end
   end