Add Null email driver (support workaround for #224)

app/assets/javascripts/app/views/channel/email_account_overview.jst.eco

@@ -46,7 +46,9 @@
       <div class="action-block action-block--flex">
         <div class="horizontal">
           <h3><%- @Icon('status', channel.status_in + " inline") %> <%- @T('Inbound') %></h3>
+          <% if channel.preferences.editable isnt false: %>
             <div class="js-editInbound btn btn--text space-left"><%- @T('Edit') %></div>
+          <% end %>
         </div>
         <table class="key-value">
           <tr>
@@ -89,7 +91,9 @@
       <div class="action-block action-block--flex">
         <div class="horizontal">
           <h3><%- @Icon('status', channel.status_out + " inline") %> <%- @T('Outbound') %></h3>
+          <% if channel.preferences.editable isnt false: %>
             <div class="js-editOutbound btn btn--text space-left"><%- @T('Edit') %></div>
+          <% end %>
         </div>
         <table class="key-value">
         <% if channel.options.outbound && channel.options.outbound.options: %>

app/models/channel/driver/null.rb

@@ -0,0 +1,22 @@
+# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
+class Channel::Driver::Null
+  def fetchable?(_channel)
+    false
+  end
+
+  def fetch(*)
+    {
+      result:  'ok',
+      fetched: 0,
+      notice:  '',
+    }
+  end
+
+  def disconnect
+    true
+  end
+
+  def self.streamable?
+    false
+  end
+end

spec/factories/channel.rb

@@ -8,6 +8,20 @@ FactoryBot.define do
     updated_by_id 1
     created_by_id 1
 
+    factory :email_channel do
+      area 'Email::Account'
+      options do
+        {
+          inbound:  {
+            adapter: 'null', options: {}
+          },
+          outbound: {
+            adapter: 'sendmail'
+          }
+        }
+      end
+    end
+
     factory :twitter_channel do
       transient do
         custom_options { {} }

spec/system/admin/channel/email_spec.rb

@@ -0,0 +1,17 @@
+require 'rails_helper'
+
+RSpec.describe 'Admin Panel > Channels > Email', type: :system, authenticated: true do
+  # https://github.com/zammad/zammad/issues/224
+  it 'hides "Edit" links when Channel#preferences[:editable] == false' do
+    # ensure that the only existing email channel
+    # has preferences == { editable: false }
+    Channel.destroy_all
+    create(:email_channel, preferences: { editable: false })
+
+    visit '/#channels/email'
+    expect(page).to have_css('#c-account h3', text: 'Inbound')  # Wait for frontend to load
+    expect(page).to have_css('#c-account h3', text: 'Outbound') # Wait for frontend to load
+
+    expect(page).not_to have_css('.js-editInbound, .js-editOutbound', text: 'Edit')
+  end
+end