Convert pushgateway client to keyword arguments

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>

lib/prometheus/client/push.rb

@@ -21,10 +21,8 @@ class Push
 
       attr_reader :job, :instance, :gateway, :path
 
-      def initialize(job, instance = nil, gateway = nil)
-        unless job
-          raise ArgumentError, "job cannot be nil"
-        end
+      def initialize(job:, instance: nil, gateway: DEFAULT_GATEWAY)
+        raise ArgumentError, "job cannot be nil" if job.nil?
 
         @mutex = Mutex.new
         @job = job

spec/prometheus/client/push_spec.rb

@@ -5,35 +5,35 @@
 describe Prometheus::Client::Push do
   let(:gateway) { 'http://localhost:9091' }
   let(:registry) { Prometheus::Client.registry }
-  let(:push) { Prometheus::Client::Push.new('test-job', nil, gateway) }
+  let(:push) { Prometheus::Client::Push.new(job: 'test-job', gateway: gateway) }
 
   describe '.new' do
     it 'returns a new push instance' do
       expect(push).to be_a(Prometheus::Client::Push)
     end
 
     it 'uses localhost as default Pushgateway' do
-      push = Prometheus::Client::Push.new('test-job')
+      push = Prometheus::Client::Push.new(job: 'test-job')
 
       expect(push.gateway).to eql('http://localhost:9091')
     end
 
     it 'allows to specify a custom Pushgateway' do
-      push = Prometheus::Client::Push.new('test-job', nil, 'http://pu.sh:1234')
+      push = Prometheus::Client::Push.new(job: 'test-job', gateway: 'http://pu.sh:1234')
 
       expect(push.gateway).to eql('http://pu.sh:1234')
     end
 
-    it 'raises an ArgumentError if the job is not provided' do
+    it 'raises an ArgumentError if the job is nil' do
       expect do
-        Prometheus::Client::Push.new(nil)
+        Prometheus::Client::Push.new(job: nil)
       end.to raise_error ArgumentError
     end
 
     it 'raises an ArgumentError if the given gateway URL is invalid' do
       ['inva.lid:1233', 'http://[invalid]'].each do |url|
         expect do
-          Prometheus::Client::Push.new('test-job', nil, url)
+          Prometheus::Client::Push.new(job: 'test-job', gateway: url)
         end.to raise_error ArgumentError
       end
     end
@@ -65,19 +65,19 @@
 
   describe '#path' do
     it 'uses the default metrics path if no instance value given' do
-      push = Prometheus::Client::Push.new('test-job')
+      push = Prometheus::Client::Push.new(job: 'test-job')
 
       expect(push.path).to eql('/metrics/job/test-job')
     end
 
     it 'uses the full metrics path if an instance value is given' do
-      push = Prometheus::Client::Push.new('bar-job', 'foo')
+      push = Prometheus::Client::Push.new(job: 'bar-job', instance: 'foo')
 
       expect(push.path).to eql('/metrics/job/bar-job/instance/foo')
     end
 
     it 'escapes non-URL characters' do
-      push = Prometheus::Client::Push.new('bar job', 'foo <my instance>')
+      push = Prometheus::Client::Push.new(job: 'bar job', instance: 'foo <my instance>')
 
       expected = '/metrics/job/bar+job/instance/foo+%3Cmy+instance%3E'
       expect(push.path).to eql(expected)