Issue sidekiq#1901: Don't crash if provided config file is empty.

Don't return result of YAML.load if false

added tests around empty config file

update changelog

Changes.md

@@ -2,6 +2,7 @@
 -----------
 
 - Add queues list for each process to the Busy page. [davetoxa, #1897]
+- Fix for crash caused by empty config file. [jordan0day, #1901]
 
 3.2.2
 -----------

lib/sidekiq/cli.rb

@@ -353,7 +353,7 @@ def write_pid
     def parse_config(cfile)
       opts = {}
       if File.exist?(cfile)
-        opts = YAML.load(ERB.new(IO.read(cfile)).result)
+        opts = YAML.load(ERB.new(IO.read(cfile)).result) || opts
         opts = opts.merge(opts.delete(environment) || {})
         parse_queues(opts, opts.delete(:queues) || [])
       else

test/test_cli.rb

@@ -241,6 +241,35 @@ class TestCli < Sidekiq::Test
       end
     end
 
+    describe 'with an empty config file' do
+      before do
+        @tmp_file = Tempfile.new('sidekiq-test')
+        @tmp_path = @tmp_file.path
+        @tmp_file.close!
+      end
+
+      after do
+        File.unlink @tmp_path if File.exist? @tmp_path
+      end
+
+      it 'takes a path' do
+        @cli.parse(['sidekiq', '-C', @tmp_path])
+        assert_equal @tmp_path, Sidekiq.options[:config_file]
+      end
+
+      it 'should have an identical options hash, except for config_file' do
+        @cli.parse(['sidekiq'])
+        old_options = Sidekiq.options.clone
+
+        @cli.parse(['sidekiq', '-C', @tmp_path])
+        new_options = Sidekiq.options.clone
+        refute_equal old_options, new_options
+
+        new_options.delete(:config_file)
+        assert_equal old_options, new_options
+      end
+    end
+
     describe 'with config file and flags' do
       before do
         # We need an actual file here.