add validator for the 'reply_by_email_enabled' site setting

config/locales/server.en.yml

@@ -1263,6 +1263,8 @@ en:
       pop3_polling_username_is_empty: "You must set a 'pop3 polling username' before enabling POP3 polling."
       pop3_polling_password_is_empty: "You must set a 'pop3 polling password' before enabling POP3 polling."
       pop3_polling_authentication_failed: "POP3 authentication failed. Please verify your pop3 credentials."
+      reply_by_email_address_is_empty: "You must set a 'reply by email address' before enabling reply by email."
+      pop3_polling_disabled: "You must first enabled POP3 polling before enabling reply by email."
 
   notification_types:
     group_mentioned: "%{group_name} was mentioned in %{link}"

config/site_settings.yml

@@ -506,7 +506,9 @@ email:
     client: true
   email_custom_headers: 'Auto-Submitted: auto-generated'
   email_subject: '[%{site_name}] %{optional_pm}%{optional_cat}%{topic_title}'
-  reply_by_email_enabled: false
+  reply_by_email_enabled:
+    default: false
+    validator: "ReplyByEmailEnabledValidator"
   reply_by_email_address:
     default: ''
     validator: "ReplyByEmailAddressValidator"

lib/validators/reply_by_email_enabled_validator.rb

@@ -0,0 +1,23 @@
+class ReplyByEmailEnabledValidator
+
+  def initialize(opts={})
+    @opts = opts
+  end
+
+  def valid_value?(val)
+    # only validate when enabling reply by email
+    return true if val == "f"
+    # ensure reply_by_email_address is configured && polling is working
+    SiteSetting.reply_by_email_address.present? &&
+    SiteSetting.pop3_polling_enabled?
+  end
+
+  def error_message
+    if SiteSetting.reply_by_email_address.blank?
+      I18n.t("site_settings.errors.reply_by_email_address_is_empty")
+    else
+      I18n.t("site_settings.errors.pop3_polling_disabled")
+    end
+  end
+
+end

spec/components/validators/reply_by_email_enabled_validator_spec.rb

@@ -0,0 +1,31 @@
+require 'rails_helper'
+
+describe ReplyByEmailEnabledValidator do
+
+  describe '#valid_value?' do
+    subject(:validator) { described_class.new }
+
+    it "only validates when enabling the setting" do
+      expect(validator.valid_value?("f")).to eq(true)
+    end
+
+    it "returns false if reply_by_email_address is missing" do
+      SiteSetting.expects(:reply_by_email_address).returns("")
+      expect(validator.valid_value?("t")).to eq(false)
+    end
+
+    it "returns false if POP3 polling is disabled" do
+      SiteSetting.expects(:reply_by_email_address).returns("foo.%{reply_key}+42@bar.com")
+      SiteSetting.expects(:pop3_polling_enabled).returns(false)
+      expect(validator.valid_value?("t")).to eq(false)
+    end
+
+    it "returns true when POP3 polling is enabled and the reply_by_email_address is configured" do
+      SiteSetting.expects(:reply_by_email_address).returns("foo.%{reply_key}+42@bar.com")
+      SiteSetting.expects(:pop3_polling_enabled).returns(true)
+      expect(validator.valid_value?("t")).to eq(true)
+    end
+
+  end
+
+end