feat: add --no-stdin flag to container attach

Signed-off-by: Subash Kotha <subash.kotha2@gmail.com>

Author: subashkotha

cmd/nerdctl/container/container_attach.go

@@ -17,6 +17,8 @@
 package container
 
 import (
+	"io"
+
 	"github.com/spf13/cobra"
 
 	containerd "github.com/containerd/containerd/v2/client"
@@ -56,6 +58,7 @@ Caveats:
 		SilenceErrors:     true,
 	}
 	cmd.Flags().String("detach-keys", consoleutil.DefaultDetachKeys, "Override the default detach keys")
+	cmd.Flags().Bool("no-stdin", false, "Do not attach STDIN")
 	return cmd
 }
 
@@ -68,9 +71,18 @@ func attachOptions(cmd *cobra.Command) (types.ContainerAttachOptions, error) {
 	if err != nil {
 		return types.ContainerAttachOptions{}, err
 	}
+	noStdin, err := cmd.Flags().GetBool("no-stdin")
+	if err != nil {
+		return types.ContainerAttachOptions{}, err
+	}
+
+	var stdin io.Reader
+	if !noStdin {
+		stdin = cmd.InOrStdin()
+	}
 	return types.ContainerAttachOptions{
 		GOptions:   globalOptions,
-		Stdin:      cmd.InOrStdin(),
+		Stdin:      stdin,
 		Stdout:     cmd.OutOrStdout(),
 		Stderr:     cmd.ErrOrStderr(),
 		DetachKeys: detachKeys,

cmd/nerdctl/container/container_attach_linux_test.go

@@ -211,3 +211,61 @@ func TestAttachForAutoRemovedContainer(t *testing.T) {
 
 	testCase.Run(t)
 }
+
+func TestAttachNoStdin(t *testing.T) {
+	testCase := nerdtest.Setup()
+
+	testCase.Cleanup = func(data test.Data, helpers test.Helpers) {
+		helpers.Anyhow("rm", "-f", data.Identifier())
+	}
+
+	testCase.Setup = func(data test.Data, helpers test.Helpers) {
+		cmd := helpers.Command("run", "-it", "--detach-keys=ctrl-p,ctrl-q", "--name", data.Identifier(),
+			testutil.CommonImage, "sh", "-c", `echo ready; sleep 5`)
+		cmd.WithPseudoTTY()
+		time.Sleep(1 * time.Second)
+		cmd.Feed(bytes.NewReader([]byte{16, 17})) // Ctrl-p, Ctrl-q to detach (https://en.wikipedia.org/wiki/C0_and_C1_control_codes)
+		cmd.Run(&test.Expected{
+			ExitCode: 0,
+			Output: func(stdout string, info string, t *testing.T) {
+				assert.Assert(t, strings.Contains(helpers.Capture("inspect", "--format", "{{.State.Running}}", data.Identifier()), "true"))
+			},
+		})
+	}
+
+	testCase.Command = func(data test.Data, helpers test.Helpers) test.TestableCommand {
+		cmd := helpers.Command("attach", "--no-stdin", data.Identifier())
+		cmd.WithPseudoTTY()
+		cmd.WithFeeder(func() io.Reader {
+			maxRetries := 30
+			retryCount := 0
+			for {
+				if retryCount >= maxRetries {
+					t.Fatalf("Container did not output 'ready' message after %d retries", maxRetries)
+					return nil
+				}
+				out := helpers.Capture("logs", data.Identifier())
+				if strings.Contains(out, "ready") {
+					break
+				}
+				time.Sleep(1 * time.Second)
+				retryCount++
+			}
+			return strings.NewReader("should-not-appear\n")
+		})
+		return cmd
+	}
+
+	testCase.Expected = func(data test.Data, helpers test.Helpers) *test.Expected {
+		return &test.Expected{
+			ExitCode: 0, // Since it's a normal exit and not detach.
+			Output: func(stdout string, info string, t *testing.T) {
+				logs := helpers.Capture("logs", data.Identifier())
+				assert.Assert(t, strings.Contains(logs, "ready"))
+				assert.Assert(t, !strings.Contains(stdout, "should-not-appear"))
+			},
+		}
+	}
+
+	testCase.Run(t)
+}

docs/command-reference.md

@@ -686,8 +686,9 @@ Usage: `nerdctl attach CONTAINER`
 Flags:
 
 - :whale: `--detach-keys`: Override the default detach keys
+- :whale: `--no-stdin`: Do not attach STDIN
 
-Unimplemented `docker attach` flags: `--no-stdin`, `--sig-proxy`
+Unimplemented `docker attach` flags: `--sig-proxy`
 
 ### :whale: nerdctl container prune
 

pkg/cmd/container/attach.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 
 	"golang.org/x/term"
 
@@ -114,9 +115,12 @@ func Attach(ctx context.Context, client *containerd.Client, req string, options
 			}
 			io.Cancel()
 		}
-		in, err := consoleutil.NewDetachableStdin(con, options.DetachKeys, closer)
-		if err != nil {
-			return err
+		var in io.Reader
+		if options.Stdin != nil {
+			in, err = consoleutil.NewDetachableStdin(con, options.DetachKeys, closer)
+			if err != nil {
+				return err
+			}
 		}
 		opt = cio.WithStreams(in, con, nil)
 	} else {