We are treating name as more like a username

Therefore it should be a unique way of identifying a user.

lib/chess/store/user.ex

@@ -20,20 +20,23 @@ defmodule Chess.Store.User do
     timestamps()
   end
 
+  @profile_attrs ~w[name email]a
+  @registration_attrs ~w[name email password]a
+
   @doc false
   def changeset(struct, params \\ %{}) do
     struct
-    |> cast(params, registration_attrs())
-    |> validate_required(registration_attrs())
-    |> unique_constraint(:email)
+    |> cast(params, @registration_attrs)
+    |> validate_required(@registration_attrs)
+    |> unique_validations()
     |> hash_password()
   end
 
   def profile_changeset(struct, params \\ %{}) do
     struct
-    |> cast(params, profile_attrs())
-    |> validate_required(profile_attrs())
-    |> unique_constraint(:email)
+    |> cast(params, @profile_attrs)
+    |> validate_required(@profile_attrs)
+    |> unique_validations()
   end
 
   def password_changeset(struct, params \\ %{}) do
@@ -43,6 +46,12 @@ defmodule Chess.Store.User do
     |> hash_password()
   end
 
+  def unique_validations(struct, params \\ %{}) do
+    struct
+    |> unique_constraint(:name)
+    |> unique_constraint(:email)
+  end
+
   def opponents(user) do
     from user in "users",
       where: user.id != ^user.id,
@@ -58,7 +67,4 @@ defmodule Chess.Store.User do
       changeset
     end
   end
-
-  defp registration_attrs, do: ~w[name email password]a
-  defp profile_attrs, do: ~w{name email}a
 end

priv/repo/migrations/20180928184135_add_unique_index_to_users_name.exs

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

test/chess/store/user_test.exs

@@ -25,7 +25,16 @@ defmodule Chess.Store.UserTest do
     end
 
     test "email must be unique" do
-      insert(:user, %{email: "zelda@hyrule.com"})
+      insert(:user, %{name: "Princess", email: "zelda@hyrule.com"})
+
+      changeset = User.changeset(%User{}, @valid_attrs)
+      {:error, changeset} = Repo.insert(changeset)
+
+      refute changeset.valid?
+    end
+
+    test "name must be unique" do
+      insert(:user, %{name: "Zelda", email: "princess@hyrule.kingdom"})
 
       changeset = User.changeset(%User{}, @valid_attrs)
       {:error, changeset} = Repo.insert(changeset)