Make sure DateTime.truncate returns DateTime when passed map (#8448)

With tests for Calendar.datetime maps being passed to DateTime functions.

2 files changed, 83 insertions, 2 deletions

diff --git a/lib/elixir/lib/calendar/datetime.ex b/lib/elixir/lib/calendar/datetime.ex
index 8e85cb21e..dcc791b91 100644
--- a/lib/elixir/lib/calendar/datetime.ex
+++ b/lib/elixir/lib/calendar/datetime.ex
@@ -1098,10 +1098,14 @@ defmodule DateTime do
   """
   @doc since: "1.6.0"
   @spec truncate(Calendar.datetime(), :microsecond | :millisecond | :second) :: t()
-  def truncate(%{microsecond: microsecond} = datetime, precision) do
+  def truncate(%DateTime{microsecond: microsecond} = datetime, precision) do
     %{datetime | microsecond: Calendar.truncate(microsecond, precision)}
   end
 
+  def truncate(%{} = datetime_map, precision) do
+    truncate(from_map(datetime_map), precision)
+  end
+
   @doc """
   Converts a given `datetime` from one calendar to another.
 
@@ -1129,10 +1133,14 @@ defmodule DateTime do
   @spec convert(Calendar.datetime(), Calendar.calendar()) ::
           {:ok, t} | {:error, :incompatible_calendars}
 
-  def convert(%{calendar: calendar} = datetime, calendar) do
+  def convert(%DateTime{calendar: calendar} = datetime, calendar) do
     {:ok, datetime}
   end
 
+  def convert(%{calendar: calendar} = datetime, calendar) do
+    {:ok, from_map(datetime)}
+  end
+
   def convert(%{calendar: dt_calendar, microsecond: {_, precision}} = datetime, calendar) do
     if Calendar.compatible_calendars?(dt_calendar, calendar) do
       result_datetime =
@@ -1228,6 +1236,22 @@ defmodule DateTime do
     Calendar.ISO.add_day_fraction_to_iso_days(iso_days, -offset, 86400)
   end
 
+  defp from_map(%{} = datetime_map) do
+    %DateTime{
+      year: datetime_map.year,
+      month: datetime_map.month,
+      day: datetime_map.day,
+      hour: datetime_map.hour,
+      minute: datetime_map.minute,
+      second: datetime_map.second,
+      microsecond: datetime_map.microsecond,
+      time_zone: datetime_map.time_zone,
+      zone_abbr: datetime_map.zone_abbr,
+      utc_offset: datetime_map.utc_offset,
+      std_offset: datetime_map.std_offset
+    }
+  end
+
   defimpl String.Chars do
     def to_string(datetime) do
       %{
diff --git a/lib/elixir/test/elixir/calendar/datetime_test.exs b/lib/elixir/test/elixir/calendar/datetime_test.exs
index 149823481..fe8c2b384 100644
--- a/lib/elixir/test/elixir/calendar/datetime_test.exs
+++ b/lib/elixir/test/elixir/calendar/datetime_test.exs
@@ -22,6 +22,10 @@ defmodule DateTimeTest do
     }
 
     assert to_string(datetime) == "2000-02-29 23:00:07-02:30 BRM Brazil/Manaus"
+    assert DateTime.to_string(datetime) == "2000-02-29 23:00:07-02:30 BRM Brazil/Manaus"
+
+    assert DateTime.to_string(Map.from_struct(datetime)) ==
+             "2000-02-29 23:00:07-02:30 BRM Brazil/Manaus"
   end
 
   test "from_iso8601/1 handles positive and negative offsets" do
@@ -256,6 +260,7 @@ defmodule DateTimeTest do
     }
 
     assert DateTime.to_unix(gregorian_0) == -62_167_219_200
+    assert DateTime.to_unix(Map.from_struct(gregorian_0)) == -62_167_219_200
 
     min_datetime = %DateTime{gregorian_0 | year: -9999}
 
@@ -311,6 +316,7 @@ defmodule DateTimeTest do
     assert DateTime.compare(datetime3, datetime3) == :eq
     assert DateTime.compare(datetime2, datetime3) == :gt
     assert DateTime.compare(datetime3, datetime1) == :lt
+    assert DateTime.compare(Map.from_struct(datetime3), Map.from_struct(datetime1)) == :lt
   end
 
   test "convert/2" do
@@ -354,6 +360,14 @@ defmodule DateTimeTest do
            |> DateTime.convert!(Calendar.ISO) == %{datetime_iso | microsecond: {123, 6}}
 
     assert DateTime.convert(datetime_iso, FakeCalendar) == {:error, :incompatible_calendars}
+
+    # Test passing non-struct map when converting to different calendar returns DateTime struct
+    assert DateTime.convert(Map.from_struct(datetime_iso), Calendar.Holocene) ==
+             {:ok, datetime_hol}
+
+    # Test passing non-struct map when converting to same calendar returns DateTime struct
+    assert DateTime.convert(Map.from_struct(datetime_iso), Calendar.ISO) ==
+             {:ok, datetime_iso}
   end
 
   test "from_iso8601/1 with tz offsets" do
@@ -469,9 +483,15 @@ defmodule DateTimeTest do
       time_zone: "Europe/Paris"
     }
 
+    datetime_map = Map.from_struct(datetime)
+
     assert DateTime.truncate(%{datetime | microsecond: {123_456, 6}}, :microsecond) ==
              %{datetime | microsecond: {123_456, 6}}
 
+    # A struct should be returned when passing a map.
+    assert DateTime.truncate(%{datetime_map | microsecond: {123_456, 6}}, :microsecond) ==
+             %{datetime | microsecond: {123_456, 6}}
+
     assert DateTime.truncate(%{datetime | microsecond: {0, 0}}, :millisecond) ==
              %{datetime | microsecond: {0, 0}}
 
@@ -524,6 +544,9 @@ defmodule DateTimeTest do
     }
 
     assert DateTime.diff(dt1, dt2) == 3_281_904_000
+
+    # Test with a non-struct map conforming to Calendar.datetime
+    assert DateTime.diff(Map.from_struct(dt1), Map.from_struct(dt2)) == 3_281_904_000
   end
 
   describe "from_naive" do
@@ -702,6 +725,25 @@ defmodule DateTimeTest do
   end
 
   describe "add" do
+    test "add with non-struct map that conforms to Calendar.datetime" do
+      dt_map = DateTime.from_naive!(~N[2018-08-28 00:00:00], "Etc/UTC") |> Map.from_struct()
+
+      assert DateTime.add(dt_map, 1, :second) == %DateTime{
+               calendar: Calendar.ISO,
+               year: 2018,
+               month: 8,
+               day: 28,
+               hour: 0,
+               minute: 0,
+               second: 1,
+               std_offset: 0,
+               time_zone: "Etc/UTC",
+               zone_abbr: "UTC",
+               utc_offset: 0,
+               microsecond: {0, 0}
+             }
+    end
+
     test "error with UTC only database and non UTC datetime" do
       dt =
         DateTime.from_naive!(~N[2018-08-28 00:00:00], "Europe/Copenhagen", FakeTimeZoneDatabase)
@@ -732,4 +774,19 @@ defmodule DateTimeTest do
                }
     end
   end
+
+  describe "to_iso8601" do
+    test "to_iso8601/2 with a normal DateTime struct" do
+      datetime = DateTime.from_naive!(~N[2018-07-01 12:34:25.123456], "Etc/UTC")
+
+      assert DateTime.to_iso8601(datetime) == "2018-07-01T12:34:25.123456Z"
+    end
+
+    test "to_iso8601/2 with a non-struct map conforming to the Calendar.datetime type" do
+      datetime_map =
+        DateTime.from_naive!(~N[2018-07-01 12:34:25.123456], "Etc/UTC") |> Map.from_struct()
+
+      assert DateTime.to_iso8601(datetime_map) == "2018-07-01T12:34:25.123456Z"
+    end
+  end
 end