Allow setting nil value in Settings::Upsert (#14228)

app/models/settings/smtp.rb

@@ -8,13 +8,13 @@ module Settings
     # the cache, or call Settings::Smtp.clear_cache
     cache_prefix { "v1" }
 
-    field :address, type: :string, default: ApplicationConfig["SMTP_ADDRESS"]
-    field :authentication, type: :string, default: ApplicationConfig["SMTP_AUTHENTICATION"],
+    field :address, type: :string, default: ApplicationConfig["SMTP_ADDRESS"].presence
+    field :authentication, type: :string, default: ApplicationConfig["SMTP_AUTHENTICATION"].presence,
                            validates: { inclusion: %w[plain login cram_md5] }
-    field :domain, type: :string, default: ApplicationConfig["SMTP_DOMAIN"]
-    field :password, type: :string, default: ApplicationConfig["SMTP_PASSWORD"]
+    field :domain, type: :string, default: ApplicationConfig["SMTP_DOMAIN"].presence
+    field :password, type: :string, default: ApplicationConfig["SMTP_PASSWORD"].presence
     field :port, type: :integer, default: ApplicationConfig["SMTP_PORT"].presence || 25
-    field :user_name, type: :string, default: ApplicationConfig["SMTP_USER_NAME"]
+    field :user_name, type: :string, default: ApplicationConfig["SMTP_USER_NAME"].presence
 
     class << self
       def settings

app/services/settings/upsert.rb

@@ -32,6 +32,8 @@ module Settings
           settings_class.public_send("#{key}=", value.to_h)
         elsif value.present?
           settings_class.public_send("#{key}=", value.strip)
+        elsif value.blank?
+          settings_class.public_send("#{key}=", nil)
         end
       rescue ActiveRecord::RecordInvalid => e
         @errors << e.message

app/validators/valid_domain_csv_validator.rb

@@ -3,6 +3,8 @@ class ValidDomainCsvValidator < ActiveModel::EachValidator
   VALID_DOMAIN = /^[a-zA-Z0-9]{1,61}[a-zA-Z0-9](?:\.[a-zA-Z]{2,})+$/.freeze
 
   def validate_each(record, attribute, value)
+    return unless value
+
     return if value.all? { |domain| domain.match?(VALID_DOMAIN) }
 
     record.errors.add(attribute, options[:message] || DEFAULT_MESSAGE)

spec/requests/admin/configs_spec.rb

@@ -793,6 +793,32 @@ RSpec.describe "/admin/customization/config", type: :request do
         end
       end
 
+      describe "SMTP configs" do
+        after { Settings::SMTP.clear_cache }
+
+        it "updates appropriate SMTP configs" do
+          expected_handle = { "address" => "smtp.example.com", "port" => "1234" }
+          post admin_settings_smtp_settings_path, params: {
+            settings_smtp: expected_handle,
+            confirmation: confirmation_message
+          }
+          expect(Settings::SMTP.address).to eq("smtp.example.com")
+          expect(Settings::SMTP.port).to eq(1234)
+        end
+
+        it "unsets appropriate SMTP config, and apply default value if applicable" do
+          Settings::SMTP.address = "smtp.example.com"
+          Settings::SMTP.port = 12_345
+          expected_handle = { "address" => "", "port" => "" }
+          post admin_settings_smtp_settings_path, params: {
+            settings_smtp: expected_handle,
+            confirmation: confirmation_message
+          }
+          expect(Settings::SMTP.address).to eq(nil)
+          expect(Settings::SMTP.port).to eq(25)
+        end
+      end
+
       describe "Sponsors" do
         it "updates the sponsor_headline" do
           headline = "basic"