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

pkg/printers/yaml_printer.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2022 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package printers
+
+import (
+	"fmt"
+	"io"
+
+	"sigs.k8s.io/yaml"
+)
+
+// YamlPrinter is a printer that prints Flux cmd outputs as yaml.
+func YamlPrinter(header []string) PrinterFunc {
+	return func(w io.Writer, args ...interface{}) error {
+		// args is 2d array of string
+		// headers is 1d array of string
+		var rows [][]string
+		for _, arg := range args {
+			switch arg := arg.(type) {
+			case []interface{}:
+				for _, v := range arg {
+					s, ok := v.([][]string)
+					if !ok {
+						return fmt.Errorf("unsupported type %T", v)
+					}
+					rows = append(rows, s...)
+				}
+			default:
+				return fmt.Errorf("unsupported type %T", arg)
+			}
+		}
+
+		var entries []map[string]interface{}
+		for _, row := range rows {
+			entry := make(map[string]interface{})
+			for j, h := range header {
+				if row[j] == "True" || row[j] == "False" {
+					entry[h] = row[j] == "True"
+				} else {
+					entry[h] = row[j]
+				}
+			}
+			entries = append(entries, entry)
+		}
+
+		if len(entries) > 0 {
+			y, err := yaml.Marshal(entries)
+			if err != nil {
+				return fmt.Errorf("error marshalling yaml %w", err)
+			}
+			fmt.Fprint(w, string(y))
+		}
+
+		return nil
+	}
+}