feat: support for YAML and JSON outputs of gwctl (#2940)

Signed-off-by: Yashvardhan Kukreja <yash.kukreja.98@gmail.com>

gwctl/cmd/describe.go

@@ -82,12 +82,13 @@ func runDescribe(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		K8sClients:    params.K8sClients,
 		PolicyManager: params.PolicyManager,
 	}
-	policiesPrinter := &printer.PoliciesPrinter{Out: params.Out, Clock: clock.RealClock{}}
-	httpRoutesPrinter := &printer.HTTPRoutesPrinter{Out: params.Out, Clock: clock.RealClock{}}
-	gwPrinter := &printer.GatewaysPrinter{Out: params.Out, Clock: clock.RealClock{}}
-	gwcPrinter := &printer.GatewayClassesPrinter{Out: params.Out, Clock: clock.RealClock{}}
-	backendsPrinter := &printer.BackendsPrinter{Out: params.Out}
-	namespacesPrinter := &printer.NamespacesPrinter{Out: params.Out, Clock: clock.RealClock{}}
+
+	policiesPrinter := &printer.PoliciesPrinter{Writer: params.Out, Clock: clock.RealClock{}}
+	httpRoutesPrinter := &printer.HTTPRoutesPrinter{Writer: params.Out, Clock: clock.RealClock{}}
+	gwPrinter := &printer.GatewaysPrinter{Writer: params.Out, Clock: clock.RealClock{}}
+	gwcPrinter := &printer.GatewayClassesPrinter{Writer: params.Out, Clock: clock.RealClock{}}
+	backendsPrinter := &printer.BackendsPrinter{Writer: params.Out}
+	namespacesPrinter := &printer.NamespacesPrinter{Writer: params.Out, Clock: clock.RealClock{}}
 
 	switch kind {
 	case "policy", "policies":

gwctl/cmd/get.go

@@ -34,6 +34,7 @@ func NewGetCommand() *cobra.Command {
 	var namespaceFlag string
 	var allNamespacesFlag bool
 	var labelSelector string
+	var outputFormat string
 
 	cmd := &cobra.Command{
 		Use:   "get {namespaces|gateways|gatewayclasses|policies|policycrds|httproutes}",
@@ -47,6 +48,7 @@ func NewGetCommand() *cobra.Command {
 	cmd.Flags().StringVarP(&namespaceFlag, "namespace", "n", "default", "")
 	cmd.Flags().BoolVarP(&allNamespacesFlag, "all-namespaces", "A", false, "If present, list requested resources from all namespaces.")
 	cmd.Flags().StringVarP(&labelSelector, "selector", "l", "", "Selector (label query) to filter on, supports '=', '==', and '!='.(e.g. -l key1=value1,key2=value2). Matching objects must satisfy all of the specified label constraints.")
+	cmd.Flags().StringVarP(&outputFormat, "output", "o", "", `Output format. Must be one of (yaml, json)`)
 
 	return cmd
 }
@@ -70,6 +72,16 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		fmt.Fprintf(os.Stderr, "failed to read flag \"selector\": %v\n", err)
 		os.Exit(1)
 	}
+	output, err := cmd.Flags().GetString("output")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to read flag \"output\": %v\n", err)
+		os.Exit(1)
+	}
+	outputFormat, err := utils.ValidateAndReturnOutputFormat(output)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
 
 	if allNs {
 		ns = ""
@@ -80,12 +92,16 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		PolicyManager: params.PolicyManager,
 	}
 	realClock := clock.RealClock{}
-	nsPrinter := &printer.NamespacesPrinter{Out: params.Out, Clock: realClock}
-	gwPrinter := &printer.GatewaysPrinter{Out: params.Out, Clock: realClock}
-	gwcPrinter := &printer.GatewayClassesPrinter{Out: params.Out, Clock: realClock}
-	policiesPrinter := &printer.PoliciesPrinter{Out: params.Out, Clock: realClock}
-	httpRoutesPrinter := &printer.HTTPRoutesPrinter{Out: params.Out, Clock: realClock}
-	backendsPrinter := &printer.BackendsPrinter{Out: params.Out, Clock: realClock}
+
+	nsPrinter := &printer.NamespacesPrinter{Writer: params.Out, Clock: realClock}
+	gwPrinter := &printer.GatewaysPrinter{Writer: params.Out, Clock: realClock}
+	gwcPrinter := &printer.GatewayClassesPrinter{Writer: params.Out, Clock: realClock}
+	policiesPrinter := &printer.PoliciesPrinter{Writer: params.Out, Clock: realClock}
+	httpRoutesPrinter := &printer.HTTPRoutesPrinter{Writer: params.Out, Clock: realClock}
+	backendsPrinter := &printer.BackendsPrinter{Writer: params.Out, Clock: realClock}
+
+	var resourceModel *resourcediscovery.ResourceModel
+	var printerImpl printer.Printer
 
 	switch kind {
 	case "namespace", "namespaces", "ns":
@@ -94,12 +110,12 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 			fmt.Fprintf(os.Stderr, "Unable to find resources that match the label selector \"%s\": %v\n", labelSelector, err)
 			os.Exit(1)
 		}
-		resourceModel, err := discoverer.DiscoverResourcesForNamespace(resourcediscovery.Filter{Labels: selector})
+		resourceModel, err = discoverer.DiscoverResourcesForNamespace(resourcediscovery.Filter{Labels: selector})
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover Namespace resources: %v\n", err)
 			os.Exit(1)
 		}
-		nsPrinter.Print(resourceModel)
+		printerImpl = nsPrinter
 
 	case "gateway", "gateways":
 		selector, err := labels.Parse(labelSelector)
@@ -111,12 +127,12 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		if len(args) > 1 {
 			filter.Name = args[1]
 		}
-		resourceModel, err := discoverer.DiscoverResourcesForGateway(filter)
+		resourceModel, err = discoverer.DiscoverResourcesForGateway(filter)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover Gateway resources: %v\n", err)
 			os.Exit(1)
 		}
-		gwPrinter.Print(resourceModel)
+		printerImpl = gwPrinter
 
 	case "gatewayclass", "gatewayclasses":
 		selector, err := labels.Parse(labelSelector)
@@ -128,20 +144,22 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		if len(args) > 1 {
 			filter.Name = args[1]
 		}
-		resourceModel, err := discoverer.DiscoverResourcesForGatewayClass(filter)
+		resourceModel, err = discoverer.DiscoverResourcesForGatewayClass(filter)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover GatewayClass resources: %v\n", err)
 			os.Exit(1)
 		}
-		gwcPrinter.Print(resourceModel)
+		printerImpl = gwcPrinter
 
 	case "policy", "policies":
 		list := params.PolicyManager.GetPolicies()
-		policiesPrinter.PrintPoliciesGetView(list)
+		policiesPrinter.PrintPolicies(list, outputFormat)
+		return
 
 	case "policycrd", "policycrds":
 		list := params.PolicyManager.GetCRDs()
-		policiesPrinter.PrintPolicyCRDsGetView(list)
+		policiesPrinter.PrintCRDs(list, outputFormat)
+		return
 
 	case "httproute", "httproutes":
 		selector, err := labels.Parse(labelSelector)
@@ -153,12 +171,12 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		if len(args) > 1 {
 			filter.Name = args[1]
 		}
-		resourceModel, err := discoverer.DiscoverResourcesForHTTPRoute(filter)
+		resourceModel, err = discoverer.DiscoverResourcesForHTTPRoute(filter)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover HTTPRoute resources: %v\n", err)
 			os.Exit(1)
 		}
-		httpRoutesPrinter.Print(resourceModel)
+		printerImpl = httpRoutesPrinter
 
 	case "backend", "backends":
 		selector, err := labels.Parse(labelSelector)
@@ -170,14 +188,17 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		if len(args) > 1 {
 			filter.Name = args[1]
 		}
-		resourceModel, err := discoverer.DiscoverResourcesForBackend(filter)
+		resourceModel, err = discoverer.DiscoverResourcesForBackend(filter)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover backend resources: %v\n", err)
 			os.Exit(1)
 		}
 		backendsPrinter.Print(resourceModel)
+		return
 
 	default:
 		fmt.Fprintf(os.Stderr, "Unrecognized RESOURCE_TYPE\n")
+		os.Exit(1)
 	}
+	printer.Print(printerImpl, resourceModel, outputFormat)
 }

gwctl/pkg/common/clients.go

@@ -131,3 +131,13 @@ func MustClientsForTest(t *testing.T, initRuntimeObjects ...runtime.Object) *K8s
 func PtrTo[T any](a T) *T {
 	return &a
 }
+
+func MapToValues[K comparable, V any](obj map[K]V) []V {
+	values := make([]V, len(obj))
+	i := 0
+	for _, v := range obj {
+		values[i] = v
+		i++
+	}
+	return values
+}

gwctl/pkg/common/testhelpers.go

@@ -17,6 +17,8 @@ limitations under the License.
 package common
 
 import (
+	"encoding/json"
+	"fmt"
 	"strings"
 
 	"github.com/google/go-cmp/cmp"
@@ -51,3 +53,21 @@ var YamlStringTransformer = cmp.Transformer("YamlLines", func(s YamlString) []st
 	}
 	return lines[start : end+1]
 })
+
+type JSONString string
+
+func (src JSONString) CmpDiff(tgt JSONString) (diff string, err error) {
+	var srcMap, targetMap map[string]interface{}
+	err = json.Unmarshal([]byte(src), &srcMap)
+	if err != nil {
+		err = fmt.Errorf("failed to unmarshal the source json: %w", err)
+		return
+	}
+	err = json.Unmarshal([]byte(tgt), &targetMap)
+	if err != nil {
+		err = fmt.Errorf("failed to unmarshal the target json: %w", err)
+		return
+	}
+
+	return cmp.Diff(srcMap, targetMap), nil
+}

gwctl/pkg/policymanager/manager.go

@@ -22,6 +22,8 @@ import (
 	"fmt"
 	"strings"
 
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -180,6 +182,8 @@ type PolicyCRD struct {
 	crd apiextensionsv1.CustomResourceDefinition
 }
 
+func (p PolicyCRD) ClientObject() client.Object { return p.CRD() }
+
 // ID returns a unique identifier for this PolicyCRD.
 func (p PolicyCRD) ID() PolicyCrdID {
 	return PolicyCrdID(p.crd.Spec.Names.Kind + "." + p.crd.Spec.Group)
@@ -220,6 +224,8 @@ type Policy struct {
 	inherited bool
 }
 
+func (p Policy) ClientObject() client.Object { return p.Unstructured() }
+
 type ObjRef struct {
 	Group     string `json:",omitempty"`
 	Kind      string `json:",omitempty"`

gwctl/pkg/printer/backends.go

@@ -29,19 +29,19 @@ import (
 
 	"sigs.k8s.io/controller-runtime/pkg/client"
 
-	"sigs.k8s.io/yaml"
-
 	"sigs.k8s.io/gateway-api/gwctl/pkg/policymanager"
 	"sigs.k8s.io/gateway-api/gwctl/pkg/resourcediscovery"
+
+	"sigs.k8s.io/yaml"
 )
 
 type BackendsPrinter struct {
-	Out   io.Writer
+	io.Writer
 	Clock clock.Clock
 }
 
 func (bp *BackendsPrinter) Print(resourceModel *resourcediscovery.ResourceModel) {
-	tw := tabwriter.NewWriter(bp.Out, 0, 0, 2, ' ', 0)
+	tw := tabwriter.NewWriter(bp, 0, 0, 2, ' ', 0)
 	row := []string{"NAMESPACE", "NAME", "TYPE", "REFERRED BY ROUTES", "AGE", "POLICIES"}
 	_, err := tw.Write([]byte(strings.Join(row, "\t") + "\n"))
 	if err != nil {
@@ -163,11 +163,11 @@ func (bp *BackendsPrinter) PrintDescribeView(resourceModel *resourcediscovery.Re
 				fmt.Fprintf(os.Stderr, "failed to marshal to yaml: %v\n", err)
 				os.Exit(1)
 			}
-			fmt.Fprint(bp.Out, string(b))
+			fmt.Fprint(bp, string(b))
 		}
 
 		if index+1 <= len(resourceModel.Backends) {
-			fmt.Fprintf(bp.Out, "\n\n")
+			fmt.Fprintf(bp, "\n\n")
 		}
 	}
 }

gwctl/pkg/printer/backends_test.go

@@ -465,8 +465,8 @@ func TestBackendsPrinter_Print(t *testing.T) {
 	}
 
 	bp := &BackendsPrinter{
-		Out:   params.Out,
-		Clock: fakeClock,
+		Writer: params.Out,
+		Clock:  fakeClock,
 	}
 
 	bp.Print(resourceModel)

gwctl/pkg/printer/common.go

@@ -20,12 +20,14 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sort"
 	"strings"
 	"text/tabwriter"
 
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/util/duration"
 	"k8s.io/utils/clock"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/yaml"
 )
 
@@ -148,3 +150,32 @@ func convertEventsSliceToTable(events []corev1.Event, clock clock.Clock) *Table
 	}
 	return table
 }
+
+type NodeResource interface {
+	ClientObject() client.Object
+}
+
+func ClientObjects[K NodeResource](nodes []K) []client.Object {
+	clientObjects := make([]client.Object, len(nodes))
+	for i, node := range nodes {
+		clientObjects[i] = node.ClientObject()
+	}
+	return clientObjects
+}
+
+func SortByString[K NodeResource](items []K) []K {
+	sort.Slice(items, func(i, j int) bool {
+		a := client.ObjectKeyFromObject(items[i].ClientObject()).String()
+		b := client.ObjectKeyFromObject(items[j].ClientObject()).String()
+		return a < b
+	})
+	return items
+}
+
+func NodeResources[K NodeResource](items []K) []NodeResource {
+	output := make([]NodeResource, len(items))
+	for i, item := range items {
+		output[i] = item
+	}
+	return output
+}