Add unique email constraint for users. Part of #101

priv/repo/migrations/20161014181536_add_unique_email_index_to_users.exs

@@ -0,0 +1,7 @@
+defmodule Ask.Repo.Migrations.AddUniqueEmailIndexToUsers do
+  use Ecto.Migration
+
+  def change do
+    create unique_index(:users, [:email])
+  end
+end

test/models/user_test.exs

@@ -1,7 +1,7 @@
 defmodule Ask.UserTest do
   use Ask.ModelCase
 
-  alias Ask.User
+  alias Ask.{User, Repo}
 
   @valid_attrs %{email: "some@content", encrypted_password: "some content"}
   @invalid_email %{email: "some content", encrypted_password: "some content"}
@@ -21,4 +21,9 @@ defmodule Ask.UserTest do
     changeset = User.changeset(%User{}, @invalid_email)
     refute changeset.valid?
   end
+
+  test "can't create two users with same email" do
+    User.changeset(%User{}, @valid_attrs) |> Repo.insert!
+    {:error, _} = User.changeset(%User{}, @valid_attrs) |> Repo.insert
+  end
 end

web/models/user.ex

@@ -19,6 +19,7 @@ defmodule Ask.User do
     struct
     |> cast(params, [:email, :encrypted_password])
     |> validate_required([:email, :encrypted_password])
+    |> unique_constraint(:email)
     |> validate_format(:email, ~r/@/)
   end
 end