Improve path handling in pushgateway client

lib/prometheus/client/push.rb

@@ -21,7 +21,10 @@ class Push
 
       attr_reader :job, :instance, :gateway, :path
 
-      def initialize(job, instance = nil, gateway = nil, **kwargs)
+      def initialize(job:, instance: nil, gateway: DEFAULT_GATEWAY, **kwargs)
+        raise ArgumentError, "job cannot be nil" if job.nil?
+        raise ArgumentError, "job cannot be empty" if job.empty?
+
         @mutex = Mutex.new
         @job = job
         @instance = instance

spec/prometheus/client/push_spec.rb

@@ -5,29 +5,41 @@
 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, open_timeout: 5, read_timeout: 30) }
+  let(:push) { Prometheus::Client::Push.new(job: 'test-job', gateway: gateway, open_timeout: 5, read_timeout: 30) }
 
   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 nil' do
+      expect do
+        Prometheus::Client::Push.new(job: nil)
+      end.to raise_error ArgumentError
+    end
+
+    it 'raises an ArgumentError if the job is empty' do
+      expect do
+        Prometheus::Client::Push.new(job: "")
+      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
@@ -59,19 +71,19 @@
 
   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)