Handle a Docker daemon without registry info

components/cli/cli/command/registry.go

@@ -28,7 +28,9 @@ func ElectAuthServer(ctx context.Context, cli Cli) string {
 	// the default registry URL might be Windows specific.
 	serverAddress := registry.IndexServer
 	if info, err := cli.Client().Info(ctx); err != nil {
-		fmt.Fprintf(cli.Out(), "Warning: failed to get default registry endpoint from daemon (%v). Using system default: %s\n", err, serverAddress)
+		fmt.Fprintf(cli.Err(), "Warning: failed to get default registry endpoint from daemon (%v). Using system default: %s\n", err, serverAddress)
+	} else if info.IndexServerAddress == "" {
+		fmt.Fprintf(cli.Err(), "Warning: Empty registry endpoint from daemon. Using system default: %s\n", serverAddress)
 	} else {
 		serverAddress = info.IndexServerAddress
 	}

components/cli/cli/command/registry_test.go

@@ -0,0 +1,79 @@
+package command_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/net/context"
+
+	// Prevents a circular import with "github.com/docker/cli/cli/internal/test"
+	. "github.com/docker/cli/cli/command"
+	"github.com/docker/cli/cli/internal/test"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/client"
+)
+
+type fakeClient struct {
+	client.Client
+	infoFunc func() (types.Info, error)
+}
+
+func (cli *fakeClient) Info(_ context.Context) (types.Info, error) {
+	if cli.infoFunc != nil {
+		return cli.infoFunc()
+	}
+	return types.Info{}, nil
+}
+
+func TestElectAuthServer(t *testing.T) {
+	testCases := []struct {
+		expectedAuthServer string
+		expectedWarning    string
+		infoFunc           func() (types.Info, error)
+	}{
+		{
+			expectedAuthServer: "https://index.docker.io/v1/",
+			expectedWarning:    "",
+			infoFunc: func() (types.Info, error) {
+				return types.Info{IndexServerAddress: "https://index.docker.io/v1/"}, nil
+			},
+		},
+		{
+			expectedAuthServer: "https://index.docker.io/v1/",
+			expectedWarning:    "Empty registry endpoint from daemon",
+			infoFunc: func() (types.Info, error) {
+				return types.Info{IndexServerAddress: ""}, nil
+			},
+		},
+		{
+			expectedAuthServer: "https://foo.bar",
+			expectedWarning:    "",
+			infoFunc: func() (types.Info, error) {
+				return types.Info{IndexServerAddress: "https://foo.bar"}, nil
+			},
+		},
+		{
+			expectedAuthServer: "https://index.docker.io/v1/",
+			expectedWarning:    "failed to get default registry endpoint from daemon",
+			infoFunc: func() (types.Info, error) {
+				return types.Info{}, errors.Errorf("error getting info")
+			},
+		},
+	}
+	for _, tc := range testCases {
+		buf := new(bytes.Buffer)
+		cli := test.NewFakeCli(&fakeClient{infoFunc: tc.infoFunc}, buf)
+		errBuf := new(bytes.Buffer)
+		cli.SetErr(errBuf)
+		server := ElectAuthServer(context.Background(), cli)
+		assert.Equal(t, tc.expectedAuthServer, server)
+		actual := errBuf.String()
+		if tc.expectedWarning == "" {
+			assert.Empty(t, actual)
+		} else {
+			assert.Contains(t, actual, tc.expectedWarning)
+		}
+	}
+}