[v13] handle empty lists for yaml and json formatted lists in tctl

lib/utils/jsontools.go

@@ -114,6 +114,24 @@ func FastMarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
 	return data, nil
 }
 
+// WriteJSONArray marshals values as a JSON array.
+func WriteJSONArray[T any](w io.Writer, values []T) error {
+	if len(values) == 0 {
+		_, err := w.Write([]byte("[]"))
+		return err
+	}
+	return WriteJSON(w, values)
+}
+
+// WriteJSONObject marshals m as a JSON object.
+func WriteJSONObject[M ~map[K]V, K comparable, V any](w io.Writer, m M) error {
+	if len(m) == 0 {
+		_, err := w.Write([]byte("{}"))
+		return err
+	}
+	return WriteJSON(w, m)
+}
+
 // WriteJSON marshals multiple documents as a JSON list with indentation.
 func WriteJSON(w io.Writer, values interface{}) error {
 	encoder := json.NewEncoder(w)
@@ -156,6 +174,10 @@ func WriteYAML(w io.Writer, values interface{}) error {
 	}
 	// first pass makes sure that all values are documents (objects or maps)
 	slice := reflect.ValueOf(values)
+	if slice.Len() == 0 {
+		_, err := w.Write([]byte("[]"))
+		return err
+	}
 	allDocs := func() bool {
 		for i := 0; i < slice.Len(); i++ {
 			if !isDoc(slice.Index(i)) {

tool/tctl/common/acl_command.go

@@ -119,7 +119,7 @@ func (c *ACLCommand) List(ctx context.Context, client auth.ClientI) error {
 		}
 	}
 
-	if len(accessLists) == 0 {
+	if len(accessLists) == 0 && c.format == teleport.Text {
 		fmt.Println("no access lists")
 		return nil
 	}
@@ -222,7 +222,7 @@ func displayAccessLists(format string, accessLists ...*accesslist.AccessList) er
 	case teleport.YAML:
 		return trace.Wrap(utils.WriteYAML(os.Stdout, accessLists))
 	case teleport.JSON:
-		return trace.Wrap(utils.WriteJSON(os.Stdout, accessLists))
+		return trace.Wrap(utils.WriteJSONArray(os.Stdout, accessLists))
 	case teleport.Text:
 		return trace.Wrap(displayAccessListsText(accessLists...))
 	}

tool/tctl/common/alert_command.go

@@ -181,7 +181,7 @@ func (c *AlertCommand) List(ctx context.Context, client auth.ClientI) error {
 		return trace.Wrap(err)
 	}
 
-	if len(alerts) == 0 {
+	if len(alerts) == 0 && c.format == teleport.Text {
 		fmt.Println("no alerts")
 		return nil
 	}

tool/tctl/common/bots_command.go

@@ -131,11 +131,10 @@ func (c *BotsCommand) ListBots(ctx context.Context, client auth.ClientI) error {
 		}
 		fmt.Println(t.AsBuffer().String())
 	} else {
-		out, err := json.MarshalIndent(users, "", "  ")
+		err := utils.WriteJSONArray(os.Stdout, users)
 		if err != nil {
 			return trace.Wrap(err, "failed to marshal users")
 		}
-		fmt.Print(string(out))
 	}
 	return nil
 }

tool/tctl/common/collection.go

@@ -166,7 +166,7 @@ func (s *serverCollection) writeYAML(w io.Writer) error {
 }
 
 func (s *serverCollection) writeJSON(w io.Writer) error {
-	return utils.WriteJSON(w, s.servers)
+	return utils.WriteJSONArray(w, s.servers)
 }
 
 type userCollection struct {

tool/tctl/common/helpers_test.go

@@ -159,6 +159,22 @@ func mustDecodeJSON[T any](t *testing.T, r io.Reader) T {
 	return out
 }
 
+func mustDecodeYAMLDocuments[T any](t *testing.T, r io.Reader, out *[]T) error {
+	decoder := yaml.NewDecoder(r)
+	for {
+		var entry T
+		if err := decoder.Decode(&entry); err != nil {
+			// Break when there are no more documents to decode
+			if err != io.EOF {
+				return err
+			}
+			break
+		}
+		*out = append(*out, entry)
+	}
+	return nil
+}
+
 func mustDecodeYAML[T any](t *testing.T, r io.Reader) T {
 	var out T
 	err := yaml.NewDecoder(r).Decode(&out)

tool/tctl/common/token_command.go

@@ -366,7 +366,7 @@ func (c *TokensCommand) List(ctx context.Context, client auth.ClientI) error {
 	if err != nil {
 		return trace.Wrap(err)
 	}
-	if len(tokens) == 0 {
+	if len(tokens) == 0 && c.format == teleport.Text {
 		fmt.Fprintln(c.stdout, "No active tokens found.")
 		return nil
 	}
@@ -376,17 +376,15 @@ func (c *TokensCommand) List(ctx context.Context, client auth.ClientI) error {
 
 	switch c.format {
 	case teleport.JSON:
-		data, err := json.MarshalIndent(tokens, "", "  ")
+		err := utils.WriteJSONArray(c.stdout, tokens)
 		if err != nil {
 			return trace.Wrap(err, "failed to marshal tokens")
 		}
-		fmt.Fprint(c.stdout, string(data))
 	case teleport.YAML:
-		data, err := yaml.Marshal(tokens)
+		err := utils.WriteYAML(c.stdout, tokens)
 		if err != nil {
 			return trace.Wrap(err, "failed to marshal tokens")
 		}
-		fmt.Fprint(c.stdout, string(data))
 	case teleport.Text:
 		for _, token := range tokens {
 			fmt.Fprintln(c.stdout, token.GetName())

tool/tctl/common/token_command_test.go

@@ -121,7 +121,9 @@ func TestTokens(t *testing.T) {
 
 		buf, err = runTokensCommand(t, fileConfig, []string{"ls", "--format", teleport.YAML})
 		require.NoError(t, err)
-		yamlOut := mustDecodeYAML[[]listedToken](t, buf)
+		yamlOut := []listedToken{}
+		err = mustDecodeYAMLDocuments(t, buf, &yamlOut)
+		require.NoError(t, err)
 		require.Len(t, yamlOut, 4)
 
 		require.Equal(t, jsonOut, yamlOut)

tool/tctl/common/user_command.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/url"
+	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -37,6 +38,7 @@ import (
 	"github.com/gravitational/teleport/lib/defaults"
 	"github.com/gravitational/teleport/lib/service/servicecfg"
 	"github.com/gravitational/teleport/lib/services"
+	"github.com/gravitational/teleport/lib/utils"
 	"github.com/gravitational/teleport/lib/utils/gcp"
 )
 
@@ -492,11 +494,10 @@ func (u *UserCommand) List(ctx context.Context, client auth.ClientI) error {
 		}
 		fmt.Println(t.AsBuffer().String())
 	} else {
-		out, err := json.MarshalIndent(users, "", "  ")
+		err := utils.WriteJSONArray(os.Stdout, users)
 		if err != nil {
 			return trace.Wrap(err, "failed to marshal users")
 		}
-		fmt.Print(string(out))
 	}
 	return nil
 }

tool/tsh/tsh.go

@@ -1617,7 +1617,7 @@ func exportSession(cf *CLIConf) error {
 
 	switch format {
 	case teleport.JSON:
-		if err := utils.WriteJSON(os.Stdout, events); err != nil {
+		if err := utils.WriteJSONArray(os.Stdout, events); err != nil {
 			return trace.Wrap(err)
 		}
 	case teleport.YAML: