Add test for version output aligning

Includes some refactoring to allow testing the output
in isolation.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/system/testdata/docker-client-version.golden

@@ -0,0 +1,9 @@
+Client:
+ Version:      18.99.5-ce
+ API version:  1.38
+ Go version:   go1.10.2
+ Git commit:   deadbeef
+ Built:        Wed May 30 22:21:05 2018
+ OS/Arch:      linux/amd64
+ Experimental: true
+ Orchestrator: swarm

cli/command/system/version.go

@@ -14,6 +14,7 @@ import (
 	"github.com/docker/cli/kubernetes"
 	"github.com/docker/cli/templates"
 	"github.com/docker/docker/api/types"
+	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	kubernetesClient "k8s.io/client-go/kubernetes"
@@ -121,19 +122,10 @@ func reformatDate(buildTime string) string {
 }
 
 func runVersion(dockerCli command.Cli, opts *versionOptions) error {
-	templateFormat := versionTemplate
-	tmpl := templates.New("version")
-	if opts.format != "" {
-		templateFormat = opts.format
-	} else {
-		tmpl = tmpl.Funcs(template.FuncMap{"getDetailsOrder": getDetailsOrder})
-	}
-
 	var err error
-	tmpl, err = tmpl.Parse(templateFormat)
+	tmpl, err := newVersionTemplate(opts.format)
 	if err != nil {
-		return cli.StatusError{StatusCode: 64,
-			Status: "Template parsing error: " + err.Error()}
+		return cli.StatusError{StatusCode: 64, Status: err.Error()}
 	}
 
 	vd := versionInfo{
@@ -200,15 +192,30 @@ func runVersion(dockerCli command.Cli, opts *versionOptions) error {
 			})
 		}
 	}
-	t := tabwriter.NewWriter(dockerCli.Out(), 15, 1, 1, ' ', 0)
-	if err2 := tmpl.Execute(t, vd); err2 != nil && err == nil {
+	if err2 := prettyPrintVersion(dockerCli, vd, tmpl); err2 != nil && err == nil {
 		err = err2
 	}
+	return err
+}
+
+func prettyPrintVersion(dockerCli command.Cli, vd versionInfo, tmpl *template.Template) error {
+	t := tabwriter.NewWriter(dockerCli.Out(), 15, 1, 1, ' ', 0)
+	err := tmpl.Execute(t, vd)
 	t.Write([]byte("\n"))
 	t.Flush()
 	return err
 }
 
+func newVersionTemplate(templateFormat string) (*template.Template, error) {
+	if templateFormat == "" {
+		templateFormat = versionTemplate
+	}
+	tmpl := templates.New("version").Funcs(template.FuncMap{"getDetailsOrder": getDetailsOrder})
+	tmpl, err := tmpl.Parse(templateFormat)
+
+	return tmpl, errors.Wrap(err, "Template parsing error")
+}
+
 func getDetailsOrder(v types.ComponentVersion) []string {
 	out := make([]string, 0, len(v.Details))
 	for k := range v.Details {

cli/command/system/version_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/gotestyourself/gotestyourself/assert"
 	is "github.com/gotestyourself/gotestyourself/assert/cmp"
+	"github.com/gotestyourself/gotestyourself/golden"
 
 	"github.com/docker/cli/internal/test"
 	"github.com/docker/docker/api"
@@ -44,6 +45,30 @@ func TestVersionWithOrchestrator(t *testing.T) {
 	assert.Check(t, is.Contains(cleanTabs(cli.OutBuffer().String()), "Orchestrator: swarm"))
 }
 
+func TestVersionAlign(t *testing.T) {
+	vi := versionInfo{
+		Client: clientVersion{
+			Version:           "18.99.5-ce",
+			APIVersion:        "1.38",
+			DefaultAPIVersion: "1.38",
+			GitCommit:         "deadbeef",
+			GoVersion:         "go1.10.2",
+			Os:                "linux",
+			Arch:              "amd64",
+			BuildTime:         "Wed May 30 22:21:05 2018",
+			Experimental:      true,
+			Orchestrator:      "swarm",
+		},
+	}
+
+	cli := test.NewFakeCli(&fakeClient{})
+	tmpl, err := newVersionTemplate("")
+	assert.NilError(t, err)
+	assert.NilError(t, prettyPrintVersion(cli, vi, tmpl))
+	assert.Check(t, golden.String(cli.OutBuffer().String(), "docker-client-version.golden"))
+	assert.Check(t, is.Equal("", cli.ErrBuffer().String()))
+}
+
 func cleanTabs(line string) string {
 	return strings.Join(strings.Fields(line), " ")
 }