cmd/headscale/cli: add printListOutput to centralise table-vs-JSON branching

Add a helper that checks the --output flag and either serialises as
JSON/YAML or invokes a table-rendering callback. This removes the
repeated format,_ := cmd.Flags().GetString("output") + if-branch from
the five list commands.

cmd/headscale/cli/api_key.go

@@ -48,19 +48,12 @@ var listAPIKeys = &cobra.Command{
 	Short:   "List the Api keys for headscale",
 	Aliases: []string{"ls", "show"},
 	RunE: grpcRunE(func(ctx context.Context, client v1.HeadscaleServiceClient, cmd *cobra.Command, args []string) error {
-		format, _ := cmd.Flags().GetString("output")
+		response, err := client.ListApiKeys(ctx, &v1.ListApiKeysRequest{})
-
-		request := &v1.ListApiKeysRequest{}
-
-		response, err := client.ListApiKeys(ctx, request)
 		if err != nil {
 			return fmt.Errorf("listing api keys: %w", err)
 		}
 
-		if format != "" {
+		return printListOutput(cmd, response.GetApiKeys(), func() error {
-			return printOutput(cmd, response.GetApiKeys(), "")
-		}
-
 			tableData := pterm.TableData{
 				{"ID", "Prefix", "Expiration", "Created"},
 			}
@@ -80,12 +73,8 @@ var listAPIKeys = &cobra.Command{
 				})
 			}
 
-		err = pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
+			return pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
-		if err != nil {
+		})
-			return fmt.Errorf("rendering table: %w", err)
-		}
-
-		return nil
 	}),
 }
 

cmd/headscale/cli/nodes.go

@@ -136,36 +136,24 @@ var listNodesCmd = &cobra.Command{
 	Short:   "List nodes",
 	Aliases: []string{"ls", "show"},
 	RunE: grpcRunE(func(ctx context.Context, client v1.HeadscaleServiceClient, cmd *cobra.Command, args []string) error {
-		format, _ := cmd.Flags().GetString("output")
 		user, err := cmd.Flags().GetString("user")
 		if err != nil {
 			return fmt.Errorf("getting user flag: %w", err)
 		}
 
-		request := &v1.ListNodesRequest{
+		response, err := client.ListNodes(ctx, &v1.ListNodesRequest{User: user})
-			User: user,
-		}
-
-		response, err := client.ListNodes(ctx, request)
 		if err != nil {
 			return fmt.Errorf("listing nodes: %w", err)
 		}
 
-		if format != "" {
+		return printListOutput(cmd, response.GetNodes(), func() error {
-			return printOutput(cmd, response.GetNodes(), "")
-		}
-
 			tableData, err := nodesToPtables(user, response.GetNodes())
 			if err != nil {
 				return fmt.Errorf("converting to table: %w", err)
 			}
 
-		err = pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
+			return pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
-		if err != nil {
+		})
-			return fmt.Errorf("rendering table: %w", err)
-		}
-
-		return nil
 	}),
 }
 
@@ -174,15 +162,12 @@ var listNodeRoutesCmd = &cobra.Command{
 	Short:   "List routes available on nodes",
 	Aliases: []string{"lsr", "routes"},
 	RunE: grpcRunE(func(ctx context.Context, client v1.HeadscaleServiceClient, cmd *cobra.Command, args []string) error {
-		format, _ := cmd.Flags().GetString("output")
 		identifier, err := cmd.Flags().GetUint64("identifier")
 		if err != nil {
 			return fmt.Errorf("getting identifier flag: %w", err)
 		}
 
-		request := &v1.ListNodesRequest{}
+		response, err := client.ListNodes(ctx, &v1.ListNodesRequest{})
-
-		response, err := client.ListNodes(ctx, request)
 		if err != nil {
 			return fmt.Errorf("listing nodes: %w", err)
 		}
@@ -202,18 +187,9 @@ var listNodeRoutesCmd = &cobra.Command{
 			return (n.GetSubnetRoutes() != nil && len(n.GetSubnetRoutes()) > 0) || (n.GetApprovedRoutes() != nil && len(n.GetApprovedRoutes()) > 0) || (n.GetAvailableRoutes() != nil && len(n.GetAvailableRoutes()) > 0)
 		})
 
-		if format != "" {
+		return printListOutput(cmd, nodes, func() error {
-			return printOutput(cmd, nodes, "")
+			return pterm.DefaultTable.WithHasHeader().WithData(nodeRoutesToPtables(nodes)).Render()
-		}
+		})
-
-		tableData := nodeRoutesToPtables(nodes)
-
-		err = pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
-		if err != nil {
-			return fmt.Errorf("rendering table: %w", err)
-		}
-
-		return nil
 	}),
 }
 

cmd/headscale/cli/preauthkeys.go

@@ -48,17 +48,12 @@ var listPreAuthKeys = &cobra.Command{
 	Short:   "List all preauthkeys",
 	Aliases: []string{"ls", "show"},
 	RunE: grpcRunE(func(ctx context.Context, client v1.HeadscaleServiceClient, cmd *cobra.Command, args []string) error {
-		format, _ := cmd.Flags().GetString("output")
-
 		response, err := client.ListPreAuthKeys(ctx, &v1.ListPreAuthKeysRequest{})
 		if err != nil {
 			return fmt.Errorf("listing preauthkeys: %w", err)
 		}
 
-		if format != "" {
+		return printListOutput(cmd, response.GetPreAuthKeys(), func() error {
-			return printOutput(cmd, response.GetPreAuthKeys(), "")
-		}
-
 			tableData := pterm.TableData{
 				{
 					"ID",
@@ -99,12 +94,8 @@ var listPreAuthKeys = &cobra.Command{
 				})
 			}
 
-		err = pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
+			return pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
-		if err != nil {
+		})
-			return fmt.Errorf("rendering table: %w", err)
-		}
-
-		return nil
 	}),
 }
 

cmd/headscale/cli/users.go

@@ -171,8 +171,6 @@ var listUsersCmd = &cobra.Command{
 	Short:   "List all the users",
 	Aliases: []string{"ls", "show"},
 	RunE: grpcRunE(func(ctx context.Context, client v1.HeadscaleServiceClient, cmd *cobra.Command, args []string) error {
-		format, _ := cmd.Flags().GetString("output")
-
 		request := &v1.ListUsersRequest{}
 
 		id, _ := cmd.Flags().GetInt64("identifier")
@@ -194,10 +192,7 @@ var listUsersCmd = &cobra.Command{
 			return fmt.Errorf("listing users: %w", err)
 		}
 
-		if format != "" {
+		return printListOutput(cmd, response.GetUsers(), func() error {
-			return printOutput(cmd, response.GetUsers(), "")
-		}
-
 			tableData := pterm.TableData{{"ID", "Name", "Username", "Email", "Created"}}
 			for _, user := range response.GetUsers() {
 				tableData = append(
@@ -212,12 +207,8 @@ var listUsersCmd = &cobra.Command{
 				)
 			}
 
-		err = pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
+			return pterm.DefaultTable.WithHasHeader().WithData(tableData).Render()
-		if err != nil {
+		})
-			return fmt.Errorf("rendering table: %w", err)
-		}
-
-		return nil
 	}),
 }
 

cmd/headscale/cli/utils.go

@@ -209,6 +209,22 @@ func printOutput(cmd *cobra.Command, result any, override string) error {
 	return nil
 }
 
+// printListOutput checks the --output flag: when a machine-readable format is
+// requested it serialises data as JSON/YAML; otherwise it calls renderTable
+// to produce the human-readable pterm table.
+func printListOutput(
+	cmd *cobra.Command,
+	data any,
+	renderTable func() error,
+) error {
+	format, _ := cmd.Flags().GetString("output")
+	if format != "" {
+		return printOutput(cmd, data, "")
+	}
+
+	return renderTable()
+}
+
 // printError writes err to stderr, formatting it as JSON/YAML when the
 // --output flag requests machine-readable output.  Used exclusively by
 // Execute() so that every error surfaces in the format the caller asked for.