Honor IO errors in list-images sub-command

cmd/airgap/listimages.go

@@ -48,8 +48,11 @@ func NewAirgapListImagesCmd() *cobra.Command {
 				return fmt.Errorf("failed to get config: %w", err)
 			}
 
+			out := cmd.OutOrStdout()
 			for _, uri := range airgap.GetImageURIs(clusterConfig.Spec, all) {
-				fmt.Fprintln(cmd.OutOrStdout(), uri)
+				if _, err := fmt.Fprintln(out, uri); err != nil {
+					return err
+				}
 			}
 			return nil
 		},

cmd/airgap/listimages_test.go

@@ -17,18 +17,18 @@ limitations under the License.
 package airgap
 
 import (
-	"bufio"
-	"bytes"
 	"errors"
 	"fmt"
-	"io"
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 	"testing/iotest"
 
+	internalio "github.com/k0sproject/k0s/internal/io"
 	"github.com/k0sproject/k0s/pkg/apis/k0s/v1beta1"
+
 	"github.com/spf13/cobra"
 
 	"github.com/stretchr/testify/assert"
@@ -44,11 +44,28 @@ func TestAirgapListImages(t *testing.T) {
 
 	defaultImage := v1beta1.DefaultEnvoyProxyImage().URI()
 
+	t.Run("HonorsIOErrors", func(t *testing.T) {
+		var writes uint
+		underTest := NewAirgapListImagesCmd()
+		underTest.SetIn(iotest.ErrReader(errors.New("unexpected read from standard input")))
+		underTest.SilenceUsage = true // Cobra writes usage to stdout on errors 🤔
+		underTest.SetOut(internalio.WriterFunc(func(p []byte) (int, error) {
+			writes++
+			return 0, assert.AnError
+		}))
+		var stderr strings.Builder
+		underTest.SetErr(&stderr)
+
+		assert.Same(t, assert.AnError, underTest.Execute())
+		assert.Equal(t, uint(1), writes, "Expected a single write to stdout")
+		assert.Equal(t, fmt.Sprintf("Error: %v\n", assert.AnError), stderr.String())
+	})
+
 	t.Run("All", func(t *testing.T) {
 		underTest, out, err := newAirgapListImagesCmdWithConfig(t, "{}", "--all")
 
 		require.NoError(t, underTest.Execute())
-		lines := intoLines(out)
+		lines := strings.Split(out.String(), "\n")
 		if runtime.GOARCH == "arm" {
 			assert.NotContains(t, lines, defaultImage)
 		} else {
@@ -88,7 +105,7 @@ spec:
 
 				require.NoError(t, underTest.Execute())
 
-				lines := intoLines(out)
+				lines := strings.Split(out.String(), "\n")
 				for _, contained := range test.contained {
 					if runtime.GOARCH == "arm" {
 						assert.NotContains(t, lines, contained)
@@ -105,24 +122,15 @@ spec:
 	})
 }
 
-func newAirgapListImagesCmdWithConfig(t *testing.T, config string, args ...string) (_ *cobra.Command, out, err *bytes.Buffer) {
+func newAirgapListImagesCmdWithConfig(t *testing.T, config string, args ...string) (_ *cobra.Command, out, err *strings.Builder) {
 	configFile := filepath.Join(t.TempDir(), "k0s.yaml")
 	require.NoError(t, os.WriteFile(configFile, []byte(config), 0644))
 
-	out, err = new(bytes.Buffer), new(bytes.Buffer)
+	out, err = new(strings.Builder), new(strings.Builder)
 	cmd := NewAirgapListImagesCmd()
 	cmd.SetArgs(append([]string{"--config=" + configFile}, args...))
 	cmd.SetIn(iotest.ErrReader(errors.New("unexpected read from standard input")))
 	cmd.SetOut(out)
 	cmd.SetErr(err)
 	return cmd, out, err
 }
-
-func intoLines(in io.Reader) (lines []string) {
-	scanner := bufio.NewScanner(in)
-	scanner.Split(bufio.ScanLines)
-	for scanner.Scan() {
-		lines = append(lines, scanner.Text())
-	}
-	return
-}