Symbolize all config.yml keys when loading

This ensures that keys in the Yaml file can be specified as either
symbols or strings, but will always be treated as symbols after loading.

It tries to use ActiveSupport's `deep_symbolize_keys!` method if
ActiveSupport is loaded, otherwise falling back to an inline version.

Closes #3672.

lib/sidekiq/cli.rb

@@ -214,6 +214,14 @@ module Sidekiq
       @environment = cli_env || ENV['RAILS_ENV'] || ENV['RACK_ENV'] || 'development'
     end
 
+    def symbolize_keys_deep!(hash)
+      hash.keys.each do |k|
+        symkey = k.respond_to?(:to_sym) ? k.to_sym : k
+        hash[symkey] = hash.delete k
+        symbolize_keys_deep! hash[symkey] if hash[symkey].kind_of? Hash
+      end
+    end
+
     alias_method :die, :exit
     alias_method :☠, :exit
 
@@ -386,7 +394,14 @@ module Sidekiq
       opts = {}
       if File.exist?(cfile)
         opts = YAML.load(ERB.new(IO.read(cfile)).result) || opts
-        opts = opts.merge(opts.delete(environment) || {})
+
+        if opts.respond_to? :deep_symbolize_keys!
+          opts.deep_symbolize_keys!
+        else
+          symbolize_keys_deep!(opts)
+        end
+
+        opts = opts.merge(opts.delete(environment.to_sym) || {})
         parse_queues(opts, opts.delete(:queues) || [])
       else
         # allow a non-existent config file so Sidekiq

test/string_config.yml

@@ -0,0 +1,10 @@
+---
+verbose:      false
+require:      ./test/fake_env.rb
+pidfile:      /tmp/sidekiq-config-test.pid
+logfile:      /tmp/sidekiq.log
+concurrency:  50
+queues:
+  - [<%="very_"%>often, 2]
+  - [seldom, 1]
+

test/test_cli.rb

@@ -194,6 +194,24 @@ class TestCli < Sidekiq::Test
       end
     end
 
+    describe 'with config file using string keys' do
+      before do
+        @cli.parse(['sidekiq', '-C', './test/string_config.yml'])
+      end
+
+      it 'parses as expected' do
+        assert_equal './test/string_config.yml', Sidekiq.options[:config_file]
+        refute Sidekiq.options[:verbose]
+        assert_equal './test/fake_env.rb', Sidekiq.options[:require]
+        assert_nil Sidekiq.options[:environment]
+        assert_equal 50, Sidekiq.options[:concurrency]
+        assert_equal '/tmp/sidekiq-config-test.pid', Sidekiq.options[:pidfile]
+        assert_equal '/tmp/sidekiq.log', Sidekiq.options[:logfile]
+        assert_equal 2, Sidekiq.options[:queues].count { |q| q == 'very_often' }
+        assert_equal 1, Sidekiq.options[:queues].count { |q| q == 'seldom' }
+      end
+    end
+
     describe 'with env based config file' do
       before do
         @cli.parse(['sidekiq', '-e', 'staging', '-C', './test/env_based_config.yml'])