fix(term): confirmation prompts on windows (#413)

This fixes confirmation prompts on windows by scanning for a line of
input and comparing that to the desired prompt. term.Confirm(...) is
refactored slightly to make it easier to test.

Fixes #347

Author: nlowe

pkg/term/alert.go

@@ -3,22 +3,42 @@ package term
 import (
 	"bufio"
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/pkg/errors"
 )
 
+var ErrConfirmationFailed = errors.New("aborted by user")
+
 // Confirm asks the user for confirmation
 func Confirm(msg, approval string) error {
-	reader := bufio.NewReader(os.Stdin)
-	fmt.Println(msg)
-	fmt.Printf("Please type '%s' to confirm: ", approval)
-	read, err := reader.ReadString('\n')
+	return confirmFrom(os.Stdin, os.Stdout, msg, approval)
+}
+
+func confirmFrom(r io.Reader, w io.Writer, msg, approval string) error {
+	reader := bufio.NewScanner(r)
+	_, err := fmt.Fprintln(w, msg)
 	if err != nil {
-		return errors.Wrap(err, "reading from stdin")
+		return errors.Wrap(err, "writing to stdout")
 	}
-	if read != approval+"\n" {
-		return errors.New("aborted by user")
+
+	_, err = fmt.Fprintf(w, "Please type '%s' to confirm: ", approval)
+	if err != nil {
+		return errors.Wrap(err, "writing to stdout")
 	}
+
+	if !reader.Scan() {
+		if err := reader.Err(); err != nil {
+			return errors.Wrap(err, "reading from stdin")
+		}
+
+		return ErrConfirmationFailed
+	}
+
+	if reader.Text() != approval {
+		return ErrConfirmationFailed
+	}
+
 	return nil
 }

pkg/term/alert_test.go

@@ -0,0 +1,38 @@
+package term
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConfirm(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected error
+	}{
+		{name: "linux yes", input: "yes\n", expected: nil},
+		{name: "windows yes", input: "yes\r\n", expected: nil},
+		{name: "linux no", input: "no\n", expected: ErrConfirmationFailed},
+		{name: "windows no", input: "no\r\n", expected: ErrConfirmationFailed},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			in := strings.NewReader(tt.input)
+			out := &strings.Builder{}
+
+			err := confirmFrom(in, out, "foo", "yes")
+
+			assert.Equal(t, "foo\nPlease type 'yes' to confirm: ", out.String())
+
+			if tt.expected != nil {
+				assert.EqualError(t, err, tt.expected.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}