Fix for casting boolean values in MySQL (#538)

lib/ecto/adapters/myxql/connection.ex

@@ -689,6 +689,10 @@ if Code.ensure_loaded?(MyXQL) do
       [expr(other, sources, query), " + 0"]
     end
 
+    defp expr(%Ecto.Query.Tagged{value: other, type: :boolean}, sources, query) do
+      ["IF(", expr(other, sources, query), ", TRUE, FALSE)"]
+    end
+
     defp expr(%Ecto.Query.Tagged{value: other, type: type}, sources, query) do
       ["CAST(", expr(other, sources, query), " AS ", ecto_cast_to_db(type, query), ?)]
     end

test/ecto/adapters/myxql_test.exs

@@ -612,6 +612,16 @@ defmodule Ecto.Adapters.MyXQLTest do
     assert all(query) == ~s{SELECT CAST(? AS char) FROM `schema` AS s0}
   end
 
+  test "boolean type true is cast with an if" do
+    query = Schema |> select([], type(^true, :boolean)) |> plan()
+    assert all(query) == ~s{SELECT IF(?, TRUE, FALSE) FROM `schema` AS s0}
+  end
+
+  test "boolean type false is cast with an if" do
+    query = Schema |> select([], type(^false, :boolean)) |> plan()
+    assert all(query) == ~s{SELECT IF(?, TRUE, FALSE) FROM `schema` AS s0}
+  end
+
   test "json_extract_path" do
     query = Schema |> select([s], json_extract_path(s.meta, [0, 1])) |> plan()
     assert all(query) == ~s{SELECT json_extract(s0.`meta`, '$[0][1]') FROM `schema` AS s0}