Freeze mutable objects assigned to constants

Author: sferik

Rakefile

@@ -2,7 +2,7 @@ require 'bundler'
 Bundler::GemHelper.install_tasks
 
 task :erd do
-  FORMAT = 'svg'
+  FORMAT = 'svg'.freeze
   `bundle exec ruby ./etc/erd.rb > ./etc/erd.dot`
   `dot -T #{FORMAT} ./etc/erd.dot -o ./etc/erd.#{FORMAT}`
 end

etc/erd.rb

@@ -1,9 +1,9 @@
 require 'twitter'
 
-COLON = ':'
-UNDERSCORE = '_'
-TAB = "\t"
-NAMESPACE = 'Twitter::'
+COLON = ':'.freeze
+UNDERSCORE = '_'.freeze
+TAB = "\t".freeze
+NAMESPACE = 'Twitter::'.freeze
 
 # Colons are invalid characters in DOT nodes.
 # Replace them with underscores.

lib/twitter/error.rb

@@ -68,13 +68,13 @@ class Error < StandardError
       502 => Twitter::Error::BadGateway,
       503 => Twitter::Error::ServiceUnavailable,
       504 => Twitter::Error::GatewayTimeout,
-    }
+    }.freeze
 
     FORBIDDEN_MESSAGES = {
       'Status is a duplicate.' => Twitter::Error::DuplicateStatus,
       'You have already favorited this status.' => Twitter::Error::AlreadyFavorited,
       'sharing is not permissible for this status (Share validations failed)' => Twitter::Error::AlreadyRetweeted,
-    }
+    }.freeze
 
     # If error code is missing see https://dev.twitter.com/overview/api/response-codes
     module Code

lib/twitter/rest/request.rb

@@ -12,7 +12,7 @@ module Twitter
   module REST
     class Request
       include Twitter::Utils
-      BASE_URL = 'https://api.twitter.com'
+      BASE_URL = 'https://api.twitter.com'.freeze
       attr_accessor :client, :headers, :options, :path, :rate_limit,
                     :request_method, :uri
       alias verb request_method
@@ -45,7 +45,7 @@ def set_multipart_options!(request_method, options)
         if request_method == :multipart_post
           key = options.delete(:key)
           file = options.delete(:file)
-          options.merge!(key => HTTP::FormData::File.new(file, filename: File.basename(file), mime_type: mime_type(File.basename(file))))
+          options[key] = HTTP::FormData::File.new(file, filename: File.basename(file), mime_type: mime_type(File.basename(file)))
           @request_method = :post
           @headers = Twitter::Headers.new(@client, @request_method, @uri).request_headers
         else

lib/twitter/streaming/event.rb

@@ -5,11 +5,11 @@ class Event
         :list_created, :list_destroyed, :list_updated, :list_member_added,
         :list_member_added, :list_member_removed, :list_user_subscribed,
         :list_user_subscribed, :list_user_unsubscribed, :list_user_unsubscribed
-      ]
+      ].freeze
 
       TWEET_EVENTS = [
         :favorite, :unfavorite
-      ]
+      ].freeze
 
       attr_reader :name, :source, :target, :target_object