feat(env): add --output json|yaml to 'helm env'

'helm env' only emits KEY="VALUE" lines, which is inconvenient for
tooling that needs the helm paths on the current system (#11909).

Add an --output/-o flag accepting env (the default, unchanged), json,
and yaml. Single-variable mode keeps printing the bare value by
default and emits a one-entry object for the structured formats.

Closes #11909

Signed-off-by: Ruslan Shaydullin <shaydullin.r.d@outlook.com>

pkg/cmd/env.go

@@ -19,10 +19,15 @@ package cmd
 import (
 	"fmt"
 	"io"
+	"log"
+	"maps"
+	"slices"
 	"sort"
+	"strings"
 
 	"github.com/spf13/cobra"
 
+	"helm.sh/helm/v4/pkg/cli/output"
 	"helm.sh/helm/v4/pkg/cmd/require"
 )
 
@@ -31,6 +36,7 @@ Env prints out all the environment information in use by Helm.
 `
 
 func newEnvCmd(out io.Writer) *cobra.Command {
+	outfmt := envFormatKeyValue
 	cmd := &cobra.Command{
 		Use:   "env",
 		Short: "helm client environment information",
@@ -44,22 +50,18 @@ func newEnvCmd(out io.Writer) *cobra.Command {
 
 			return noMoreArgsComp()
 		},
-		Run: func(_ *cobra.Command, args []string) {
+		RunE: func(_ *cobra.Command, args []string) error {
 			envVars := settings.EnvVars()
 
-			if len(args) == 0 {
+			if len(args) == 1 {
-				// Sort the variables by alphabetical order.
+				return outfmt.writeSingle(out, args[0], envVars[args[0]])
-				// This allows for a constant output across calls to 'helm env'.
-				keys := getSortedEnvVarKeys()
-
-				for _, k := range keys {
-					fmt.Fprintf(out, "%s=\"%s\"\n", k, envVars[k])
-				}
-			} else {
-				fmt.Fprintf(out, "%s\n", envVars[args[0]])
 			}
+			return outfmt.write(out, envVars)
 		},
 	}
+
+	bindEnvOutputFlag(cmd, &outfmt)
+
 	return cmd
 }
 
@@ -74,3 +76,92 @@ func getSortedEnvVarKeys() []string {
 
 	return keys
 }
+
+// envFormat is the set of output formats supported by 'helm env'. The
+// KEY="VALUE" shell format predates the structured formats and stays the
+// default; it is not part of output.Format because no other command emits it.
+type envFormat string
+
+const (
+	envFormatKeyValue envFormat = "env"
+	envFormatJSON     envFormat = "json"
+	envFormatYAML     envFormat = "yaml"
+)
+
+func envFormats() []string {
+	return []string{string(envFormatKeyValue), string(envFormatJSON), string(envFormatYAML)}
+}
+
+func envFormatsWithDesc() map[string]string {
+	return map[string]string{
+		string(envFormatKeyValue): `Output result in KEY="VALUE" format`,
+		string(envFormatJSON):     "Output result in JSON format",
+		string(envFormatYAML):     "Output result in YAML format",
+	}
+}
+
+// String, Set and Type make envFormat usable as a pflag.Value.
+func (o *envFormat) String() string { return string(*o) }
+
+func (o *envFormat) Type() string { return "format" }
+
+func (o *envFormat) Set(s string) error {
+	if !slices.Contains(envFormats(), s) {
+		return output.ErrInvalidFormatType
+	}
+	*o = envFormat(s)
+	return nil
+}
+
+// write prints every variable in the given format.
+func (o envFormat) write(out io.Writer, envVars map[string]string) error {
+	switch o {
+	case envFormatKeyValue:
+		// Sort the variables by alphabetical order.
+		// This allows for a constant output across calls to 'helm env'.
+		for _, k := range slices.Sorted(maps.Keys(envVars)) {
+			fmt.Fprintf(out, "%s=\"%s\"\n", k, envVars[k])
+		}
+		return nil
+	case envFormatJSON:
+		return output.EncodeJSON(out, envVars)
+	case envFormatYAML:
+		return output.EncodeYAML(out, envVars)
+	}
+	return output.ErrInvalidFormatType
+}
+
+// writeSingle prints one variable. The key=value format keeps the historic
+// behavior of printing the bare value only.
+func (o envFormat) writeSingle(out io.Writer, key, value string) error {
+	switch o {
+	case envFormatKeyValue:
+		fmt.Fprintf(out, "%s\n", value)
+		return nil
+	case envFormatJSON:
+		return output.EncodeJSON(out, map[string]string{key: value})
+	case envFormatYAML:
+		return output.EncodeYAML(out, map[string]string{key: value})
+	}
+	return output.ErrInvalidFormatType
+}
+
+func bindEnvOutputFlag(cmd *cobra.Command, varRef *envFormat) {
+	cmd.Flags().VarP(varRef, outputFlag, "o",
+		"prints the output in the specified format. Allowed values: "+strings.Join(envFormats(), ", "))
+
+	err := cmd.RegisterFlagCompletionFunc(outputFlag, func(_ *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {
+		var formatNames []string
+		for format, desc := range envFormatsWithDesc() {
+			formatNames = append(formatNames, fmt.Sprintf("%s\t%s", format, desc))
+		}
+
+		// Sort the results to get a deterministic order for the tests
+		sort.Strings(formatNames)
+		return formatNames, cobra.ShellCompDirectiveNoFileComp
+	})
+
+	if err != nil {
+		log.Fatal(err)
+	}
+}

pkg/cmd/env_test.go

@@ -17,6 +17,10 @@ limitations under the License.
 package cmd
 
 import (
+	"bytes"
+	"encoding/json"
+	"regexp"
+	"strings"
 	"testing"
 )
 
@@ -25,10 +29,139 @@ func TestEnv(t *testing.T) {
 		name:   "completion for env",
 		cmd:    "__complete env ''",
 		golden: "output/env-comp.txt",
+	}, {
+		name:   "completion for env output flag",
+		cmd:    "__complete env --output ''",
+		golden: "output/env-output-comp.txt",
+	}, {
+		name:      "env with invalid output format",
+		cmd:       "env --output table",
+		golden:    "output/env-output-invalid.txt",
+		wantError: true,
 	}}
 	runTestCmd(t, tests)
 }
 
+func TestEnvOutputDefault(t *testing.T) {
+	// Pin the default format: without --output, every line must keep the
+	// historic KEY="VALUE" shape. The values are machine-specific, so
+	// assert the shape rather than compare against a golden file.
+	_, out, err := executeActionCommand("env")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !strings.Contains(out, `HELM_BIN="`) {
+		t.Errorf("expected HELM_BIN in default output, got %q", out)
+	}
+	lineRe := regexp.MustCompile(`^[A-Z0-9_]+=".*"$`)
+	for line := range strings.SplitSeq(strings.TrimSuffix(out, "\n"), "\n") {
+		if !lineRe.MatchString(line) {
+			t.Errorf("line %q does not match KEY=\"VALUE\" format", line)
+		}
+	}
+
+	// Single-variable mode without --output keeps printing the bare value.
+	_, out, err = executeActionCommand("env HELM_BURST_LIMIT")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != "100\n" {
+		t.Errorf("expected %q, got %q", "100\n", out)
+	}
+}
+
+func TestEnvOutputJSON(t *testing.T) {
+	// The full listing contains machine-specific paths, so validate the
+	// shape instead of comparing against a golden file.
+	_, out, err := executeActionCommand("env --output json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var envVars map[string]string
+	if err := json.Unmarshal([]byte(out), &envVars); err != nil {
+		t.Fatalf("expected valid JSON output, got %q: %s", out, err)
+	}
+	if _, ok := envVars["HELM_BIN"]; !ok {
+		t.Errorf("expected HELM_BIN in JSON output, got %v", envVars)
+	}
+}
+
+func TestEnvFormatWrite(t *testing.T) {
+	envVars := map[string]string{
+		"HELM_BIN":       "/usr/local/bin/helm",
+		"HELM_DEBUG":     "false",
+		"HELM_NAMESPACE": "default",
+	}
+
+	tests := []struct {
+		name   string
+		format envFormat
+		want   string
+	}{{
+		name:   "key=value format",
+		format: envFormatKeyValue,
+		want: `HELM_BIN="/usr/local/bin/helm"
+HELM_DEBUG="false"
+HELM_NAMESPACE="default"
+`,
+	}, {
+		name:   "json format",
+		format: envFormatJSON,
+		want:   `{"HELM_BIN":"/usr/local/bin/helm","HELM_DEBUG":"false","HELM_NAMESPACE":"default"}` + "\n",
+	}, {
+		name:   "yaml format",
+		format: envFormatYAML,
+		want: `HELM_BIN: /usr/local/bin/helm
+HELM_DEBUG: "false"
+HELM_NAMESPACE: default
+`,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			if err := tt.format.write(&buf, envVars); err != nil {
+				t.Fatal(err)
+			}
+			if got := buf.String(); got != tt.want {
+				t.Errorf("expected %q, got %q", tt.want, got)
+			}
+		})
+	}
+}
+
+func TestEnvFormatWriteSingle(t *testing.T) {
+	tests := []struct {
+		name   string
+		format envFormat
+		want   string
+	}{{
+		name:   "key=value format prints the bare value",
+		format: envFormatKeyValue,
+		want:   "default\n",
+	}, {
+		name:   "json format",
+		format: envFormatJSON,
+		want:   `{"HELM_NAMESPACE":"default"}` + "\n",
+	}, {
+		name:   "yaml format",
+		format: envFormatYAML,
+		want:   "HELM_NAMESPACE: default\n",
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			if err := tt.format.writeSingle(&buf, "HELM_NAMESPACE", "default"); err != nil {
+				t.Fatal(err)
+			}
+			if got := buf.String(); got != tt.want {
+				t.Errorf("expected %q, got %q", tt.want, got)
+			}
+		})
+	}
+}
+
 func TestEnvFileCompletion(t *testing.T) {
 	checkFileCompletion(t, "env", false)
 	checkFileCompletion(t, "env HELM_BIN", false)

pkg/cmd/testdata/output/env-output-comp.txt

@@ -0,0 +1,5 @@
+env	Output result in KEY="VALUE" format
+json	Output result in JSON format
+yaml	Output result in YAML format
+:4
+Completion ended with directive: ShellCompDirectiveNoFileComp

pkg/cmd/testdata/output/env-output-invalid.txt

@@ -0,0 +1 @@
+Error: invalid argument "table" for "-o, --output" flag: invalid format type