Follow-up to enhance login prompt

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Author: AkihiroSuda

cmd/nerdctl/login.go

@@ -17,13 +17,16 @@
 package main
 
 import (
+	"bufio"
 	"context"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"net/url"
+	"os"
 	"strings"
+	"syscall"
 
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/remotes/docker"
@@ -35,6 +38,7 @@ import (
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/registry"
 	"golang.org/x/net/context/ctxhttp"
+	"golang.org/x/term"
 
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -341,3 +345,21 @@ func ConfigureAuthentification(authConfig *types.AuthConfig, options *loginOptio
 
 	return nil
 }
+
+func readUsername() (string, error) {
+	var fd *os.File
+	if term.IsTerminal(int(syscall.Stdin)) {
+		fd = os.Stdin
+	} else {
+		return "", fmt.Errorf("stdin is not a terminal (Hint: use `nerdctl login --username=USERNAME --password-stdin`)")
+	}
+
+	reader := bufio.NewReader(fd)
+	username, err := reader.ReadString('\n')
+	if err != nil {
+		return "", fmt.Errorf("error reading username: %w", err)
+	}
+	username = strings.TrimSpace(username)
+
+	return username, nil
+}

cmd/nerdctl/login_unix.go

@@ -20,10 +20,8 @@
 package main
 
 import (
-	"bufio"
 	"fmt"
 	"os"
-	"strings"
 	"syscall"
 
 	"golang.org/x/term"
@@ -48,26 +46,3 @@ func readPassword() (string, error) {
 
 	return string(bytePassword), nil
 }
-
-func readUsername() (string, error) {
-	var fd *os.File
-	if term.IsTerminal(syscall.Stdin) {
-		fd = os.Stdin
-	} else {
-		tty, err := os.Open("/dev/tty")
-		if err != nil {
-			return "", fmt.Errorf("error allocating terminal: %w", err)
-		}
-		defer tty.Close()
-		fd = tty
-	}
-
-	reader := bufio.NewReader(fd)
-	username, err := reader.ReadString('\n')
-	if err != nil {
-		return "", fmt.Errorf("error reading username: %w", err)
-	}
-	username = strings.TrimSpace(username)
-
-	return username, nil
-}

cmd/nerdctl/login_windows.go

@@ -17,10 +17,7 @@
 package main
 
 import (
-	"bufio"
 	"fmt"
-	"os"
-	"strings"
 	"syscall"
 
 	"golang.org/x/term"
@@ -40,21 +37,3 @@ func readPassword() (string, error) {
 
 	return string(bytePassword), nil
 }
-
-func readUsername() (string, error) {
-	var fd *os.File
-	if term.IsTerminal(int(syscall.Stdin)) {
-		fd = os.Stdin
-	} else {
-		return "", fmt.Errorf("error allocating terminal")
-	}
-
-	reader := bufio.NewReader(fd)
-	username, err := reader.ReadString('\n')
-	if err != nil {
-		return "", fmt.Errorf("error reading username: %w", err)
-	}
-	username = strings.TrimSpace(username)
-
-	return username, nil
-}