fix(prompt): fail fast when stdin is not a terminal

go.mod

@@ -22,6 +22,7 @@ require (
 	go.uber.org/zap v1.28.0
 	golang.org/x/crypto v0.52.0
 	golang.org/x/oauth2 v0.36.0
+	golang.org/x/term v0.43.0
 )
 
 require (
@@ -62,7 +63,6 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/net v0.54.0 // indirect
 	golang.org/x/sys v0.45.0 // indirect
-	golang.org/x/term v0.43.0 // indirect
 	golang.org/x/text v0.37.0 // indirect
 	golang.org/x/tools v0.44.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1

pkg/prompt/prompter.go

@@ -4,12 +4,27 @@
 package prompt
 
 import (
+	"errors"
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/AlecAivazis/survey/v2"
+	"golang.org/x/term"
 )
 
+// ErrNonInteractive is returned when a prompt is needed but stdin is not a
+// terminal. survey blocks forever on an open pipe (CI, agent shells, cron),
+// so fail fast instead.
+var ErrNonInteractive = errors.New("stdin is not a terminal")
+
+func ensureTerminal(message string) error {
+	if term.IsTerminal(int(os.Stdin.Fd())) {
+		return nil
+	}
+	return fmt.Errorf("cannot prompt %q: %w; pass the required flags (see --help) or use -i=false", message, ErrNonInteractive)
+}
+
 type prompter struct{}
 
 // New creates a new prompter
@@ -20,6 +35,10 @@ func New() Prompter {
 const defaultPageSize = 10
 
 func (p *prompter) Select(message string, defaultValue string, options []string) (result int, err error) {
+	if err := ensureTerminal(message); err != nil {
+		return 0, err
+	}
+
 	q := &survey.Select{
 		Message:  message,
 		Options:  options,
@@ -43,6 +62,10 @@ func (p *prompter) Select(message string, defaultValue string, options []string)
 }
 
 func (p *prompter) MultiSelect(message string, defaultValues, options []string) (results []int, err error) {
+	if err := ensureTerminal(message); err != nil {
+		return nil, err
+	}
+
 	q := &survey.MultiSelect{
 		Message:  message,
 		Options:  options,
@@ -72,6 +95,10 @@ func (p *prompter) MultiSelect(message string, defaultValues, options []string)
 }
 
 func (p *prompter) Input(prompt, defaultValue string) (result string, err error) {
+	if err := ensureTerminal(prompt); err != nil {
+		return "", err
+	}
+
 	err = survey.AskOne(&survey.Input{
 		Message: prompt,
 		Default: defaultValue,
@@ -81,6 +108,10 @@ func (p *prompter) Input(prompt, defaultValue string) (result string, err error)
 }
 
 func (p *prompter) InputWithHelp(prompt, defaultValue, help string) (result string, err error) {
+	if err := ensureTerminal(prompt); err != nil {
+		return "", err
+	}
+
 	err = survey.AskOne(&survey.Input{
 		Message: prompt,
 		Default: defaultValue,
@@ -91,6 +122,10 @@ func (p *prompter) InputWithHelp(prompt, defaultValue, help string) (result stri
 }
 
 func (p *prompter) Confirm(prompt string, defaultValue bool) (bool, error) {
+	if err := ensureTerminal(prompt); err != nil {
+		return false, err
+	}
+
 	res := defaultValue
 	confirm := survey.Confirm{
 		Message: prompt,
@@ -110,6 +145,10 @@ func (p *prompter) ConfirmDeletion(requiredValue string) error {
 		Message: fmt.Sprintf("Type %s to confirm deletion:", requiredValue),
 	}
 
+	if err := ensureTerminal(input.Message); err != nil {
+		return err
+	}
+
 	validator := func(val interface{}) error {
 		if str := val.(string); !strings.EqualFold(str, requiredValue) {
 			return fmt.Errorf("you entered %s", str)

pkg/prompt/prompter_test.go

@@ -0,0 +1,93 @@
+package prompt_test
+
+import (
+	"errors"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"github.com/zeabur/cli/pkg/prompt"
+)
+
+// withPipeStdin replaces os.Stdin with the read end of a pipe whose write end
+// stays open, like a CI step or an agent shell that never sends input.
+func withPipeStdin(t *testing.T) {
+	t.Helper()
+
+	r, w, err := os.Pipe()
+	require.NoError(t, err)
+
+	orig := os.Stdin
+	os.Stdin = r
+	t.Cleanup(func() {
+		os.Stdin = orig
+		_ = w.Close()
+		_ = r.Close()
+	})
+}
+
+func requireFailsFast(t *testing.T, call func() error) {
+	t.Helper()
+
+	done := make(chan error, 1)
+	go func() { done <- call() }()
+
+	select {
+	case err := <-done:
+		require.True(t, errors.Is(err, prompt.ErrNonInteractive), "got %v", err)
+	case <-time.After(3 * time.Second):
+		t.Fatal("prompt blocked on a non-terminal stdin")
+	}
+}
+
+func TestPrompterFailsWithoutTerminal(t *testing.T) {
+	p := prompt.New()
+
+	t.Run("Select", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			_, err := p.Select("Select a service", "a", []string{"a", "b"})
+			return err
+		})
+	})
+
+	t.Run("MultiSelect", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			_, err := p.MultiSelect("Select services", nil, []string{"a", "b"})
+			return err
+		})
+	})
+
+	t.Run("Input", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			_, err := p.Input("Name", "")
+			return err
+		})
+	})
+
+	t.Run("InputWithHelp", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			_, err := p.InputWithHelp("Name", "", "help")
+			return err
+		})
+	})
+
+	t.Run("Confirm", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			_, err := p.Confirm("Continue?", false)
+			return err
+		})
+	})
+
+	t.Run("ConfirmDeletion", func(t *testing.T) {
+		withPipeStdin(t)
+		requireFailsFast(t, func() error {
+			return p.ConfirmDeletion("my-service")
+		})
+	})
+}