From ec237550245449802ff9d7d1a4b35c4550821dca Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <103478229+wangxiaoxuan273@users.noreply.github.com>
Date: Fri, 15 Mar 2024 14:48:58 +0800
Subject: [PATCH] fix: make --output - implies --no-tty (#1286)

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 cmd/oras/internal/option/common.go      | 13 +++++++-
 cmd/oras/internal/option/common_test.go | 44 +++++++++++++++++++++++++
 cmd/oras/root/blob/fetch.go             |  6 +++-
 3 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/cmd/oras/internal/option/common.go b/cmd/oras/internal/option/common.go
index 7cb14a2c0..9cd7b622c 100644
--- a/cmd/oras/internal/option/common.go
+++ b/cmd/oras/internal/option/common.go
@@ -25,6 +25,8 @@ import (
 	"oras.land/oras/internal/trace"
 )
 
+const NoTTYFlag = "no-tty"
+
 // Common option struct.
 type Common struct {
 	Debug   bool
@@ -38,7 +40,7 @@ type Common struct {
 func (opts *Common) ApplyFlags(fs *pflag.FlagSet) {
 	fs.BoolVarP(&opts.Debug, "debug", "d", false, "output debug logs (implies --no-tty)")
 	fs.BoolVarP(&opts.Verbose, "verbose", "v", false, "verbose output")
-	fs.BoolVarP(&opts.noTTY, "no-tty", "", false, "[Preview] do not show progress output")
+	fs.BoolVarP(&opts.noTTY, NoTTYFlag, "", false, "[Preview] do not show progress output")
 }
 
 // WithContext returns a new FieldLogger and an associated Context derived from ctx.
@@ -63,3 +65,12 @@ func (opts *Common) parseTTY(f *os.File) error {
 	}
 	return nil
 }
+
+// UpdateTTY updates the TTY value, given the status of --no-tty flag and output
+// path value.
+func (opts *Common) UpdateTTY(flagPresent bool, toSTDOUT bool) {
+	ttyEnforced := flagPresent && !opts.noTTY
+	if opts.noTTY || (toSTDOUT && !ttyEnforced) {
+		opts.TTY = nil
+	}
+}
diff --git a/cmd/oras/internal/option/common_test.go b/cmd/oras/internal/option/common_test.go
index 6a035a820..2949fb448 100644
--- a/cmd/oras/internal/option/common_test.go
+++ b/cmd/oras/internal/option/common_test.go
@@ -16,6 +16,8 @@ limitations under the License.
 package option
 
 import (
+	"os"
+	"reflect"
 	"testing"
 
 	"github.com/spf13/pflag"
@@ -28,3 +30,45 @@ func TestCommon_FlagsInit(t *testing.T) {
 
 	ApplyFlags(&test, pflag.NewFlagSet("oras-test", pflag.ExitOnError))
 }
+
+func TestCommon_UpdateTTY(t *testing.T) {
+	testTTY := &os.File{}
+	tests := []struct {
+		name        string
+		flagPresent bool
+		toSTDOUT    bool
+		noTTY       bool
+		expectedTTY *os.File
+	}{
+		{
+			"output to STDOUT, --no-tty flag not used, reset TTY", false, true, false, nil,
+		},
+		{
+			"output to STDOUT, --no-tty set to true, reset TTY", true, true, true, nil,
+		},
+		{
+			"output to STDOUT, --no-tty set to false", true, true, false, testTTY,
+		},
+		{
+			"not output to STDOUT, --no-tty flag not used", false, false, false, testTTY,
+		},
+		{
+			"not output to STDOUT, --no-tty set to true, reset TTY", true, false, true, nil,
+		},
+		{
+			"not output to STDOUT, --no-tty set to false", true, false, false, testTTY,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			opts := &Common{
+				noTTY: tt.noTTY,
+				TTY:   testTTY,
+			}
+			opts.UpdateTTY(tt.flagPresent, tt.toSTDOUT)
+			if !reflect.DeepEqual(opts.TTY, tt.expectedTTY) {
+				t.Fatalf("tt.TTY got %v, want %v", opts.TTY, tt.expectedTTY)
+			}
+		})
+	}
+}
diff --git a/cmd/oras/root/blob/fetch.go b/cmd/oras/root/blob/fetch.go
index 72cb3a256..f81c822fa 100644
--- a/cmd/oras/root/blob/fetch.go
+++ b/cmd/oras/root/blob/fetch.go
@@ -77,7 +77,11 @@ Example - Fetch and print a blob from OCI image layout archive file 'layout.tar'
 				return errors.New("`--output -` cannot be used with `--descriptor` at the same time")
 			}
 			opts.RawReference = args[0]
-			return option.Parse(&opts)
+			err := option.Parse(&opts)
+			if err == nil {
+				opts.UpdateTTY(cmd.Flags().Changed(option.NoTTYFlag), opts.outputPath == "-")
+			}
+			return err
 		},
 		Aliases: []string{"get"},
 		RunE: func(cmd *cobra.Command, args []string) error {