Fix system df issues with -f and -v

Fixed the issue of `--format` and `--verbose` flags being allowed in
combination with one another.

Implemented functionality for `--format json` or `--format '{{ json }}' `.

Implemented command-completion help for `--format`.

Fixes: #16204

Signed-off-by: Jake Correnti <jcorrenti13@gmail.com>

cmd/podman/system/df.go

@@ -1,6 +1,7 @@
 package system
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"os"
@@ -9,6 +10,7 @@ import (
 
 	"github.com/containers/common/pkg/completion"
 	"github.com/containers/common/pkg/report"
+	"github.com/containers/podman/v4/cmd/podman/common"
 	"github.com/containers/podman/v4/cmd/podman/registry"
 	"github.com/containers/podman/v4/cmd/podman/validate"
 	"github.com/containers/podman/v4/pkg/domain/entities"
@@ -46,7 +48,7 @@ func init() {
 
 	formatFlagName := "format"
 	flags.StringVar(&dfOptions.Format, formatFlagName, "", "Pretty-print images using a Go template")
-	_ = dfSystemCommand.RegisterFlagCompletionFunc(formatFlagName, completion.AutocompleteNone)
+	_ = dfSystemCommand.RegisterFlagCompletionFunc(formatFlagName, common.AutocompleteFormat(&dfSummary{}))
 }
 
 func df(cmd *cobra.Command, args []string) error {
@@ -55,6 +57,10 @@ func df(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
+	if dfOptions.Format != "" && dfOptions.Verbose {
+		return errors.New("Cannot combine --format and --verbose flags")
+	}
+
 	if dfOptions.Verbose {
 		return printVerbose(cmd, reports)
 	}
@@ -139,6 +145,9 @@ func printSummary(cmd *cobra.Command, reports *entities.SystemDfReport) error {
 
 	var err error
 	if cmd.Flags().Changed("format") {
+		if report.IsJSON(dfOptions.Format) {
+			return printJSON(dfSummaries)
+		}
 		rpt, err = rpt.Parse(report.OriginUser, dfOptions.Format)
 	} else {
 		row := "{{range . }}{{.Type}}\t{{.Total}}\t{{.Active}}\t{{.Size}}\t{{.Reclaimable}}\n{{end -}}"
@@ -150,6 +159,16 @@ func printSummary(cmd *cobra.Command, reports *entities.SystemDfReport) error {
 	return writeTemplate(rpt, hdrs, dfSummaries)
 }
 
+func printJSON(data interface{}) error {
+	bytes, err := json.MarshalIndent(data, "", "    ")
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(string(bytes))
+	return nil
+}
+
 func printVerbose(cmd *cobra.Command, reports *entities.SystemDfReport) error { //nolint:interfacer
 	rpt := report.New(os.Stdout, cmd.Name())
 	defer rpt.Flush()

test/e2e/system_df_test.go

@@ -110,4 +110,24 @@ var _ = Describe("podman system df", func() {
 		Expect(session.LineInOutputContains("Reclaimable"))
 		Expect(session.IsJSONOutputValid())
 	})
+
+	It("podman system df --format with --verbose", func() {
+		session := podmanTest.Podman([]string{"system", "df", "--format", "json", "--verbose"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).ShouldNot(Exit(0))
+	})
+
+	It("podman system df --format json", func() {
+		session := podmanTest.Podman([]string{"create", ALPINE})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+
+		session = podmanTest.Podman([]string{"system", "df", "--format", "json"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+		Expect(session.LineInOutputContains("Size"))
+		Expect(session.LineInOutputContains("Reclaimable"))
+		Expect(session.IsJSONOutputValid())
+	})
+
 })