feat(flux get): add --output flag, yaml only

Copied the flag syntax from kubectl --output so it can be extended later
without breaking changes.

It's not integrated terribly well, but the next step would be to
abstract the printing so we can switch out printers more cleanly and
also pick which information is rendered for each printing format, and I
do not know go or this codebase well enough to do that yet.

Signed-off-by: Mara Furland <mara@fur.land>

cmd/flux/get.go

@@ -68,6 +68,7 @@ type GetFlags struct {
 	statusSelector string
 	labelSelector  string
 	watch          bool
+	outputFormat   string
 }
 
 var getArgs GetFlags
@@ -81,6 +82,7 @@ func init() {
 		"specify the status condition name and the desired state to filter the get result, e.g. ready=false")
 	getCmd.PersistentFlags().StringVarP(&getArgs.labelSelector, "label-selector", "l", "",
 		"filter objects by label selector")
+	getCmd.PersistentFlags().StringVarP(&getArgs.outputFormat, "output", "o", "table", "Output format. One of: (table, yaml), default: table")
 	rootCmd.AddCommand(getCmd)
 }
 
@@ -168,6 +170,26 @@ func (get getCommand) run(cmd *cobra.Command, args []string) error {
 		})
 	}
 
+	outputFormat := getArgs.outputFormat
+
+	switch outputFormat {
+	case "yaml":
+	case "table":
+	case "":
+		outputFormat = "table"
+	default:
+		return fmt.Errorf("unknown output format: '%s'", outputFormat)
+	}
+
+	if outputFormat != "table" {
+		if getArgs.noHeader {
+			return fmt.Errorf("cannot set no-header in %s output", outputFormat)
+		}
+		if getArgs.watch {
+			return fmt.Errorf("cannot set watch mode in %s output", outputFormat)
+		}
+	}
+
 	getAll := cmd.Use == "all"
 
 	if getArgs.watch {
@@ -198,25 +220,31 @@ func (get getCommand) run(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 
+	displayNamespaces := getArgs.allNamespaces || outputFormat != "table"
+
 	var header []string
 	if !getArgs.noHeader {
-		header = get.list.headers(getArgs.allNamespaces)
+		header = get.list.headers(displayNamespaces)
 	}
 
-	rows, err := getRowsToPrint(getAll, get.list)
+	rows, err := getRowsToPrint(getAll, displayNamespaces, get.list)
 	if err != nil {
 		return err
 	}
 
-	err = printers.TablePrinter(header).Print(cmd.OutOrStdout(), rows)
+	switch outputFormat {
+	case "yaml":
+		err = printers.YamlPrinter(header).Print(cmd.OutOrStdout(), rows)
+	case "table":
+		err = printers.TablePrinter(header).Print(cmd.OutOrStdout(), rows)
+		if getAll && err != nil {
+			fmt.Println()
+		}
+	}
 	if err != nil {
 		return err
 	}
 
-	if getAll {
-		fmt.Println()
-	}
-
 	return nil
 }
 
@@ -227,7 +255,7 @@ func namespaceNameOrAny(allNamespaces bool, namespaceName string) string {
 	return fmt.Sprintf("%q", namespaceName)
 }
 
-func getRowsToPrint(getAll bool, list summarisable) ([][]string, error) {
+func getRowsToPrint(getAll bool, displayNamespace bool, list summarisable) ([][]string, error) {
 	noFilter := true
 	var conditionType, conditionStatus string
 	if getArgs.statusSelector != "" {
@@ -242,7 +270,7 @@ func getRowsToPrint(getAll bool, list summarisable) ([][]string, error) {
 	var rows [][]string
 	for i := 0; i < list.len(); i++ {
 		if noFilter || list.statusSelectorMatches(i, conditionType, conditionStatus) {
-			row := list.summariseItem(i, getArgs.allNamespaces, getAll)
+			row := list.summariseItem(i, displayNamespace, getAll)
 			rows = append(rows, row)
 		}
 	}
@@ -277,7 +305,7 @@ func watchUntil(ctx context.Context, w watch.Interface, get *getCommand) (bool,
 		if !getArgs.noHeader {
 			header = sink.headers(getArgs.allNamespaces)
 		}
-		rows, err := getRowsToPrint(false, sink)
+		rows, err := getRowsToPrint(false, getArgs.allNamespaces, sink)
 		if err != nil {
 			return false, err
 		}

cmd/flux/get_test.go

@@ -49,6 +49,11 @@ func Test_GetCmd(t *testing.T) {
 			args:     `-l "sharding.fluxcd.io/key notin (shard1, shard2)"`,
 			expected: "testdata/get/get_label_two.golden",
 		},
+		{
+			name:     "yaml output",
+			args:     `--output yaml`,
+			expected: "testdata/get/get_yaml.golden",
+		},
 	}
 
 	for _, tt := range tests {

cmd/flux/testdata/get/get_yaml.golden

@@ -0,0 +1,18 @@
+- Message: 'Fetched revision: main@sha1:696f056d'
+  Name: podinfo
+  Namespace: flux-system-15
+  Ready: true
+  Revision: main@sha1:696f056d
+  Suspended: false
+- Message: 'Fetched revision: main@sha1:696f056d'
+  Name: podinfo-shard1
+  Namespace: flux-system-15
+  Ready: true
+  Revision: main@sha1:696f056d
+  Suspended: false
+- Message: 'Fetched revision: main@sha1:696f056d'
+  Name: podinfo-shard2
+  Namespace: flux-system-15
+  Ready: true
+  Revision: main@sha1:696f056d
+  Suspended: false