Update :utc_datetime handling

lib/ecto/adapters/sqlite3.ex

@@ -241,24 +241,19 @@ defmodule Ecto.Adapters.SQLite3 do
 
   @impl Ecto.Adapter
   def loaders(:utc_datetime_usec, type) do
-    [&Codec.datetime_decode/1, type]
+    [&Codec.utc_datetime_decode/1, type]
   end
 
   @impl Ecto.Adapter
   def loaders(:utc_datetime, type) do
-    [&Codec.datetime_decode/1, type]
+    [&Codec.utc_datetime_decode/1, type]
   end
 
   @impl Ecto.Adapter
   def loaders(:naive_datetime, type) do
     [&Codec.naive_datetime_decode/1, type]
   end
 
-  @impl Ecto.Adapter
-  def loaders(:datetime, type) do
-    [&Codec.datetime_decode/1, type]
-  end
-
   @impl Ecto.Adapter
   def loaders(:date, type) do
     [&Codec.date_decode/1, type]
@@ -326,11 +321,26 @@ defmodule Ecto.Adapters.SQLite3 do
     [type, &Codec.time_encode/1]
   end
 
+  @impl Ecto.Adapter
+  def dumpers(:utc_datetime, type) do
+    [type, &Codec.utc_datetime_encode/1]
+  end
+
+  @impl Ecto.Adapter
+  def dumpers(:utc_datetime_usec, type) do
+    [type, &Codec.utc_datetime_encode/1]
+  end
+
   @impl Ecto.Adapter
   def dumpers(:naive_datetime, type) do
     [type, &Codec.naive_datetime_encode/1]
   end
 
+  @impl Ecto.Adapter
+  def dumpers(:naive_datetime_usec, type) do
+    [type, &Codec.naive_datetime_encode/1]
+  end
+
   @impl Ecto.Adapter
   def dumpers({:array, _}, type) do
     [type, &Codec.json_encode/1]

lib/ecto/adapters/sqlite3/codec.ex

@@ -43,17 +43,13 @@ defmodule Ecto.Adapters.SQLite3.Codec do
 
   def decimal_decode(_), do: :error
 
-  def datetime_decode(nil), do: {:ok, nil}
-
-  def datetime_decode(val) do
-    # TODO: Should we be preserving the timezone? SQLite3 stores everything
-    #       shifted to UTC. sqlite_ecto2 used a custom field type "TEXT_DATETIME"
-    #       to preserve the original string inserted. But I don't know if that
-    #       is desirable or not.
-    #
-    #       @warmwaffles 2021-02-28
-    case DateTime.from_iso8601(val) do
-      {:ok, dt, _offset} -> {:ok, dt}
+  def utc_datetime_decode(nil), do: {:ok, nil}
+
+  def utc_datetime_decode(val) do
+    with {:ok, naive} <- NaiveDateTime.from_iso8601(val),
+         {:ok, dt} <- DateTime.from_naive(naive, "Etc/UTC") do
+      {:ok, dt}
+    else
       _ -> :error
     end
   end
@@ -95,6 +91,11 @@ defmodule Ecto.Adapters.SQLite3.Codec do
     {:ok, value}
   end
 
+  # Ecto does check this already, so there should be no need to handle errors
+  def utc_datetime_encode(%{time_zone: "Etc/UTC"} = value) do
+    {:ok, NaiveDateTime.to_iso8601(value)}
+  end
+
   def naive_datetime_encode(value) do
     {:ok, NaiveDateTime.to_iso8601(value)}
   end

test/ecto/adapters/sqlite3/codec_test.exs

@@ -80,4 +80,24 @@ defmodule Ecto.Adapters.SQLite3.CodecTest do
       {:ok, ^decimal} = Codec.decimal_decode(1.2)
     end
   end
+
+  describe ".utc_datetime_decode/1" do
+    test "nil" do
+      assert {:ok, nil} = Codec.utc_datetime_decode(nil)
+    end
+
+    test "string" do
+      {:ok, dt} = DateTime.from_naive(~N[2021-08-25 10:58:59Z], "Etc/UTC")
+      assert {:ok, ^dt} = Codec.utc_datetime_decode("2021-08-25 10:58:59")
+
+      {:ok, dt} = DateTime.from_naive(~N[2021-08-25 10:58:59.111111], "Etc/UTC")
+      assert {:ok, ^dt} = Codec.utc_datetime_decode("2021-08-25 10:58:59.111111")
+    end
+
+    test "ignores timezone offset if present" do
+      {:ok, dt} = DateTime.from_naive(~N[2021-08-25 10:58:59.111111], "Etc/UTC")
+      assert {:ok, ^dt} = Codec.utc_datetime_decode("2021-08-25 10:58:59.111111Z")
+      assert {:ok, ^dt} = Codec.utc_datetime_decode("2021-08-25 10:58:59.111111+02:30")
+    end
+  end
 end