Validate batch invitation users one-by-one

Until now, one invalid email address in a batch upload (CSV) would raise
an ambiguous error and give the user no information about what went
wrong.

Now, if the batch encounters a validation problem, it returns to the
original form as before but also displays a more helpful error message.

This is a small improvement which avoids some of the complexities of
what might be even more helpful error reports (e.g. listing one or all
of the invalid email addresses).

app/controllers/batch_invitations_controller.rb

@@ -54,6 +54,11 @@ def create
       end
       batch_user = BatchInvitationUser.new(batch_user_args)
 
+      unless batch_user.valid?
+        flash[:alert] = batch_users_error_message(batch_user)
+        return render :new
+      end
+
       @batch_invitation.batch_invitation_users << batch_user
     end
 
@@ -91,4 +96,14 @@ def grant_default_permissions(batch_invitation)
       batch_invitation.grant_permission(default_permission)
     end
   end
+
+  def batch_users_error_message(batch_user)
+    e = batch_user.errors.first
+
+    if e.attribute == :email
+      "One or more emails were invalid"
+    else
+      e.full_message
+    end
+  end
 end

test/controllers/batch_invitations_controller_test.rb

@@ -131,6 +131,15 @@ def users_csv(filename = "users.csv")
       end
     end
 
+    context "the CSV contains one or more email addresses that aren't valid" do
+      should "redisplay the form and show a flash message" do
+        post :create, params: { batch_invitation: { user_names_and_emails: users_csv("users_with_non_valid_emails.csv") }, user: { supported_permission_ids: [] } }
+
+        assert_template :new
+        assert_match(/One or more emails were invalid/i, flash[:alert])
+      end
+    end
+
     context "the CSV has all the fields, but not in the expected order" do
       should "process the fields by name" do
         post :create, params: { batch_invitation: { user_names_and_emails: users_csv("reversed_users.csv") }, user: { supported_permission_ids: [] } }

test/controllers/fixtures/users_with_non_valid_emails.csv

@@ -0,0 +1,5 @@
+Name,Email
+Raphael Gupta,[email protected]
+Bolormaa Śniegowski,@bolo
+Flora Gao,[email protected]
+Aureliusz Clemente,aureliusz@examplegovuk