image/tree: Respect NO_COLOR env variable

Do not use the fancy colored output if NO_COLOR variable is set to 1
following the https://no-color.org/ convention.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli/command/image/tree.go

@@ -292,7 +292,7 @@ func printImageTree(outs command.Streams, view treeView) {
 			Width: func() int {
 				maxChipsWidth := 0
 				for _, chip := range possibleChips {
-					s := chip.String(isTerm)
+					s := out.Sprint(chip)
 					l := tui.Width(s)
 					maxChipsWidth += l
 				}
@@ -308,9 +308,9 @@ func printImageTree(outs command.Streams, view treeView) {
 				var b strings.Builder
 				for _, chip := range possibleChips {
 					if chip.check(d) {
-						b.WriteString(chip.String(isTerm))
+						b.WriteString(out.Sprint(chip))
 					} else {
-						b.WriteString(chipPlaceholder.String(isTerm))
+						b.WriteString(out.Sprint(chipPlaceholder))
 					}
 				}
 				return b.String()

cli/command/image/tree_test.go

@@ -15,6 +15,7 @@ func TestPrintImageTreeAnsiTty(t *testing.T) {
 		stdoutTty    bool
 		stderrTty    bool
 		expectedAnsi bool
+		noColorEnv   bool
 	}{
 		{
 			name:      "non-terminal",
@@ -80,6 +81,24 @@ func TestPrintImageTreeAnsiTty(t *testing.T) {
 
 			expectedAnsi: false,
 		},
+		{
+			name:      "no-color-env",
+			stdinTty:  false,
+			stdoutTty: false,
+			stderrTty: false,
+
+			noColorEnv:   true,
+			expectedAnsi: false,
+		},
+		{
+			name:      "no-color-env-terminal",
+			stdinTty:  true,
+			stdoutTty: true,
+			stderrTty: true,
+
+			noColorEnv:   true,
+			expectedAnsi: false,
+		},
 	}
 
 	mockView := treeView{
@@ -115,6 +134,11 @@ func TestPrintImageTreeAnsiTty(t *testing.T) {
 			cli.In().SetIsTerminal(tc.stdinTty)
 			cli.Out().SetIsTerminal(tc.stdoutTty)
 			cli.Err().SetIsTerminal(tc.stderrTty)
+			if tc.noColorEnv {
+				t.Setenv("NO_COLOR", "1")
+			} else {
+				t.Setenv("NO_COLOR", "")
+			}
 
 			printImageTree(cli, mockView)
 
@@ -123,9 +147,9 @@ func TestPrintImageTreeAnsiTty(t *testing.T) {
 
 			hasAnsi := strings.Contains(out, "\x1b[")
 			if tc.expectedAnsi {
-				assert.Check(t, hasAnsi, "Output should contain ANSI escape codes")
+				assert.Check(t, hasAnsi, "Output should contain ANSI escape codes, output: %s", out)
 			} else {
-				assert.Check(t, !hasAnsi, "Output should not contain ANSI escape codes")
+				assert.Check(t, !hasAnsi, "Output should not contain ANSI escape codes, output: %s", out)
 			}
 		})
 	}

docs/reference/commandline/docker.md

@@ -130,6 +130,8 @@ line:
 | `DOCKER_TLS`                  | Enable TLS for connections made by the `docker` CLI (equivalent of the `--tls` command-line option). Set to a non-empty value to enable TLS. Note that TLS is enabled automatically if any of the other TLS options are set.                                      |
 | `DOCKER_TLS_VERIFY`           | When set Docker uses TLS and verifies the remote. This variable is used both by the `docker` CLI and the [`dockerd` daemon](https://docs.docker.com/reference/cli/dockerd/)                                                                                       |
 | `BUILDKIT_PROGRESS`           | Set type of progress output (`auto`, `plain`, `tty`, `rawjson`) when [building](https://docs.docker.com/reference/cli/docker/image/build/) with [BuildKit backend](https://docs.docker.com/build/buildkit/). Use plain to show container output (default `auto`). |
+| `NO_COLOR`                    | Disable any ANSI escape codes in the output in accordance with https://no-color.org/
+                                                                                                             |
 
 Because Docker is developed using Go, you can also use any environment
 variables used by the Go runtime. In particular, you may find these useful:

internal/tui/note.go

@@ -28,7 +28,7 @@ func withHeader(header Str) noteOptions {
 }
 
 func (o Output) printNoteWithOptions(format string, args []any, opts ...noteOptions) {
-	if o.isTerminal {
+	if !o.noColor {
 		// TODO: Handle all flags
 		format = strings.ReplaceAll(format, "--platform", ColorFlag.Apply("--platform"))
 	}
@@ -51,7 +51,7 @@ func (o Output) printNoteWithOptions(format string, args []any, opts ...noteOpti
 		}
 
 		l := line
-		if o.isTerminal {
+		if !o.noColor {
 			l = aec.Italic.Apply(l)
 		}
 		_, _ = fmt.Fprintln(o, l)

internal/tui/output.go

@@ -5,6 +5,7 @@ package tui
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/docker/cli/cli/streams"
 	"github.com/morikuni/aec"
@@ -12,7 +13,7 @@ import (
 
 type Output struct {
 	*streams.Out
-	isTerminal bool
+	noColor bool
 }
 
 type terminalPrintable interface {
@@ -20,24 +21,28 @@ type terminalPrintable interface {
 }
 
 func NewOutput(out *streams.Out) Output {
+	noColor := !out.IsTerminal()
+	if os.Getenv("NO_COLOR") != "" {
+		noColor = true
+	}
 	return Output{
-		Out:        out,
-		isTerminal: out.IsTerminal(),
+		Out:     out,
+		noColor: noColor,
 	}
 }
 
 func (o Output) Color(clr aec.ANSI) aec.ANSI {
-	if o.isTerminal {
-		return clr
+	if o.noColor {
+		return ColorNone
 	}
-	return ColorNone
+	return clr
 }
 
 func (o Output) Sprint(all ...any) string {
 	var out []any
 	for _, p := range all {
 		if s, ok := p.(terminalPrintable); ok {
-			out = append(out, s.String(o.isTerminal))
+			out = append(out, s.String(!o.noColor))
 		} else {
 			out = append(out, p)
 		}
@@ -47,7 +52,7 @@ func (o Output) Sprint(all ...any) string {
 
 func (o Output) PrintlnWithColor(clr aec.ANSI, args ...any) {
 	msg := o.Sprint(args...)
-	if o.isTerminal {
+	if !o.noColor {
 		msg = clr.Apply(msg)
 	}
 	_, _ = fmt.Fprintln(o.Out, msg)