Improve error messages for type validation in migrations (#484)

* Remove suggestion to use Ecto.Type in migrations

* Improve invalid migration type error messages

* Fix tests for error message changes

Author: v0idpwn

lib/ecto/migration.ex

@@ -1395,9 +1395,7 @@ defmodule Ecto.Migration do
   defp validate_type!(type) when is_atom(type) do
     case Atom.to_string(type) do
       "Elixir." <> _ ->
-        raise ArgumentError,
-          "#{inspect type} is not a valid database type, " <>
-          "please use an atom like :string, :text and so on"
+        raise_invalid_migration_type!(type)
       _ ->
         :ok
     end
@@ -1416,17 +1414,23 @@ defmodule Ecto.Migration do
   end
 
   defp validate_type!(type) do
+    raise_invalid_migration_type!(type)
+  end
+
+  defp raise_invalid_migration_type!(type) do
     raise ArgumentError, """
     invalid migration type: #{inspect(type)}. Expected one of:
 
       * an atom, such as :string
       * a quoted atom, such as :"integer unsigned"
-      * an Ecto.Type, such as Ecto.UUID
-      * a tuple of the above, such as {:array, :integer} or {:array, Ecto.UUID}
+      * a tuple representing a composite type, such as {:array, :integer} or {:map, :string}
       * a reference, such as references(:users)
 
-    All Ecto types are allowed and properly translated.
-    All other types are sent to the database as is.
+    Ecto types are automatically translated to database types. All other types
+    are sent to the database as is.
+
+    Types defined through Ecto.Type or Ecto.ParameterizedType aren't allowed,
+    use their underlying types instead.
     """
   end
 

test/ecto/migration_test.exs

@@ -146,7 +146,7 @@ defmodule Ecto.MigrationTest do
   end
 
   test "chokes on alias types" do
-    assert_raise ArgumentError, ~r"Ecto.DateTime is not a valid database type", fn ->
+    assert_raise ArgumentError, ~r"invalid migration type: Ecto.DateTime", fn ->
       add(:hello, Ecto.DateTime)
     end
   end
@@ -413,7 +413,7 @@ defmodule Ecto.MigrationTest do
   end
 
   test "forward: column modifications invoke type validations" do
-    assert_raise ArgumentError, ~r"Ecto.DateTime is not a valid database type", fn ->
+    assert_raise ArgumentError, ~r"invalid migration type: Ecto.DateTime", fn ->
       alter table(:posts) do
         modify(:hello, Ecto.DateTime)
       end