feat: Add --tag flag to filter services in tsuru service list (#234)

* feat: Add --tag flag to filter services in tsuru service list

* refactor: flag to filter services instances

* fix(tests): syntax error and shadowed declaration in service list test

tsuru/client/services.go

@@ -34,6 +34,7 @@ type serviceFilter struct {
 	plan      string
 	service   string
 	teamOwner string
+	tags      cmd.StringSliceFlag
 }
 
 func (f *serviceFilter) queryString() (url.Values, error) {
@@ -53,6 +54,9 @@ func (f *serviceFilter) queryString() (url.Values, error) {
 	if f.service != "" {
 		result.Set("service", f.service)
 	}
+	for _, tag := range f.tags {
+		result.Add("tag", tag)
+	}
 	return result, nil
 }
 
@@ -88,7 +92,9 @@ func (c *ServiceList) Flags() *gnuflag.FlagSet {
 		c.fs.BoolVar(&c.simplified, "q", false, "Display only service instances name")
 		c.fs.BoolVar(&c.json, "json", false, "Display in JSON format")
 		c.fs.BoolVar(&c.justServiceNames, "j", false, "Display just service names")
-
+		tagMessage := "Filter services by tag. Can be used multiple times"
+		c.fs.Var(&c.filter.tags, "tag", tagMessage)
+		c.fs.Var(&c.filter.tags, "g", tagMessage)
 	}
 	return c.fs
 }
@@ -171,9 +177,11 @@ func (s ServiceList) Run(ctx *cmd.Context) error {
 	if hasPool {
 		header = append(header, "Pool")
 	}
+	hasServiceWithInstances := false
 	table.Headers = tablecli.Row(header)
 	for _, s := range services {
 		for _, instance := range s.ServiceInstances {
+			hasServiceWithInstances = true
 			row := []string{s.Service, instance.Name}
 			if hasPool {
 				row = append(row, instance.Pool)
@@ -182,6 +190,9 @@ func (s ServiceList) Run(ctx *cmd.Context) error {
 			table.AddRow(r)
 		}
 	}
+	if !hasServiceWithInstances {
+		return nil
+	}
 
 	_, err = ctx.Stdout.Write(table.Bytes())
 	return err

tsuru/client/services_test.go

@@ -155,6 +155,54 @@ func (s *S) TestServiceList(c *check.C) {
 
 }
 
+func (s *S) TestServiceListWithTags(c *check.C) {
+	var stdout, stderr bytes.Buffer
+	output, err := json.Marshal([]service.ServiceModel{
+		{
+			Service: "mysql",
+			ServiceInstances: []service.ServiceInstance{
+				{
+					Name: "mysql01",
+				},
+			},
+		},
+	})
+	c.Assert(err, check.IsNil)
+
+	ctx := cmd.Context{
+		Args:   []string{},
+		Stdout: &stdout,
+		Stderr: &stderr,
+	}
+
+	trans := cmdtest.ConditionalTransport{
+		Transport: cmdtest.Transport{Message: string(output), Status: http.StatusOK},
+		CondFunc: func(req *http.Request) bool {
+			err = req.ParseForm()
+			c.Assert(err, check.IsNil)
+
+			tags := req.Form["tag"]
+			c.Assert(tags, check.DeepEquals, []string{"tag1", "tag2"})
+
+			return strings.HasSuffix(req.URL.Path, "/services/instances")
+		},
+	}
+	s.setupFakeTransport(&trans)
+	command := ServiceList{}
+	command.Flags().Parse(true, []string{"--tag", "tag1", "--tag", "tag2"})
+	err = command.Run(&ctx)
+	c.Assert(err, check.IsNil)
+
+	table := stdout.String()
+
+	c.Assert(table, check.Equals, `+---------+----------+
+| Service | Instance |
++---------+----------+
+| mysql   | mysql01  |
++---------+----------+
+`)
+}
+
 func (s *S) TestServiceListWithPool(c *check.C) {
 	var stdout, stderr bytes.Buffer
 	output, err := json.Marshal([]service.ServiceModel{