Add Ruby config file option to installer

To replace the YAML config file people need to know they can configure
the gem with a Ruby config file too. Add this option to the installer so
people can choose this config option when installing AppSignal in their
application.

I've made it the first listed method as it's the most flexible
configuration method. The YAML file option has the "legacy" label next
to it now to discourage people from using it.

.changesets/add-ruby-config-file-method-to-installer.md

@@ -0,0 +1,6 @@
+---
+bump: patch
+type: add
+---
+
+Add the `config/appsignal.rb` Ruby config file method to installer, `appsignal install`.

lib/appsignal/cli/install.rb

@@ -229,35 +229,49 @@ def install_for_unknown_framework(config)
           done_notice
         end
 
-        def configure(config, environments, name_overwritten)
+        def configure(config, environments, name_overwritten) # rubocop:disable Metrics/AbcSize
           install_for_capistrano
 
           ENV["APPSIGNAL_APP_ENV"] = "development"
 
           puts "How do you want to configure AppSignal?"
-          puts "  (1) a config file"
-          puts "  (2) environment variables"
+          puts "  (1) a Ruby config file"
+          puts "  (2) a YAML config file (legacy)"
+          puts "  (3) environment variables"
           puts
           puts "  See our docs for information on the different configuration methods: "
           puts "  https://docs.appsignal.com/ruby/configuration.html"
           puts
-          loop do
-            print "  Choose (1/2): "
+          loop do # rubocop:disable Metrics/BlockLength
+            print "  Choose (1-3): "
             case ask_for_input
             when "1"
               puts
-              print "Writing config file"
+              print "Writing Ruby config file"
               periods
               puts
-              puts colorize "  Config file written to config/appsignal.yml", :green
-              write_config_file(
+              write_ruby_config_file(
                 :push_api_key => config[:push_api_key],
                 :app_name => config[:name],
                 :environments => environments
               )
+              puts colorize "  Config file written to config/appsignal.rb", :green
               puts
               break
             when "2"
+              puts
+              print "Writing YAML config file"
+              periods
+              puts
+              write_yaml_config_file(
+                :push_api_key => config[:push_api_key],
+                :app_name => config[:name],
+                :environments => environments
+              )
+              puts colorize "  Config file written to config/appsignal.yml", :green
+              puts
+              break
+            when "3"
               ENV["APPSIGNAL_ACTIVE"] = "true"
               ENV["APPSIGNAL_PUSH_API_KEY"] = config[:push_api_key]
               ENV["APPSIGNAL_APP_NAME"] = config[:name]
@@ -325,17 +339,37 @@ def rails_environments
           ).map { |o| File.basename(o, ".rb") }.sort - EXCLUDED_ENVIRONMENTS
         end
 
-        def write_config_file(data)
-          filename = File.join(
+        def write_ruby_config_file(data)
+          template = File.join(
+            File.dirname(__FILE__),
+            "../../../resources/appsignal.rb.erb"
+          )
+          write_config_file(
+            template,
+            File.join(Dir.pwd, "config/appsignal.rb"),
+            data
+          )
+        end
+
+        def write_yaml_config_file(data)
+          template = File.join(
             File.dirname(__FILE__),
             "../../../resources/appsignal.yml.erb"
           )
-          file_contents = File.read(filename)
+          write_config_file(
+            template,
+            File.join(Dir.pwd, "config/appsignal.yml"),
+            data
+          )
+        end
+
+        def write_config_file(template_path, path, data)
+          file_contents = File.read(template_path)
           template = ERB.new(file_contents, :trim_mode => "-")
           config = template.result(OpenStruct.new(data).instance_eval { binding })
 
           FileUtils.mkdir_p(File.join(Dir.pwd, "config"))
-          File.write(File.join(Dir.pwd, "config/appsignal.yml"), config)
+          File.write(path, config)
         end
 
         def new_config

resources/appsignal.rb.erb

@@ -0,0 +1,32 @@
+# AppSignal Ruby gem configuration
+# Visit our documentation for a list of all available configuration options.
+# https://docs.appsignal.com/ruby/configuration/options.html
+Appsignal.configure do |config|
+  config.activate_if_environment(<%= environments.map(&:inspect).join(", ") %>)
+  config.name = <%= app_name.inspect %>
+  # The application's Push API key
+  # We recommend removing this line and setting this option with the
+  # APPSIGNAL_PUSH_API_KEY environment variable instead.
+  # https://docs.appsignal.com/ruby/configuration/options.html#option-push_api_key
+  config.push_api_key = "<%= push_api_key %>"
+
+  # Actions that should not be monitored by AppSignal
+  # config.ignore_actions << "ApplicationController#isup"
+
+  # Errors that should not be recorded by AppSignal
+  # For more information see our docs:
+  # https://docs.appsignal.com/ruby/configuration/ignore-errors.html
+  # config.ignore_errors += [
+  #   "Exception",
+  #   "NoMemoryError",
+  #   "ScriptError",
+  #   "LoadError",
+  #   "NotImplementedError",
+  #   "SyntaxError",
+  #   "SecurityError",
+  #   "SignalException",
+  #   "Interrupt",
+  #   "SystemExit",
+  #   "SystemStackError"
+  # ]
+end