fix docker version --format=json not outputting json format

The --format=json option was added for all inspect commands, but was not
implemented for "docker version". This patch implements the missing option.

Before this patch:

    docker version --format=json
    json

With this patch:

    docker version --format=json
    {"Client":{"Platform":{"Name":""},"Version":"24.0.0-dev","ApiVersion":"..."}}

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

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

@@ -0,0 +1 @@
+{"Client":{"Platform":{"Name":""},"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","Context":"my-context"},"Server":{"Platform":{"Name":"Docker Enterprise Edition (EE) 2.0"},"Components":[{"Name":"Engine","Version":"17.06.2-ee-15","Details":{"ApiVersion":"1.30","Arch":"amd64","BuildTime":"Mon Jul  9 23:38:38 2018","Experimental":"false","GitCommit":"64ddfa6","GoVersion":"go1.8.7","MinAPIVersion":"1.12","Os":"linux"}},{"Name":"Universal Control Plane","Version":"17.06.2-ee-15","Details":{"ApiVersion":"1.30","Arch":"amd64","BuildTime":"Mon Jul  2 21:24:07 UTC 2018","GitCommit":"4513922","GoVersion":"go1.9.4","MinApiVersion":"1.20","Os":"linux","Version":"3.0.3-tp2"}},{"Name":"Kubernetes","Version":"1.8+","Details":{"buildDate":"2018-04-26T16:51:21Z","compiler":"gc","gitCommit":"8d637aedf46b9c21dde723e29c645b9f27106fa5","gitTreeState":"clean","gitVersion":"v1.8.11-docker-8d637ae","goVersion":"go1.8.3","major":"1","minor":"8+","platform":"linux/amd64"}},{"Name":"Calico","Version":"v3.0.8","Details":{"cni":"v2.0.6","kube-controllers":"v2.0.5","node":"v3.0.8"}}],"Version":"","ApiVersion":"","GitCommit":"","GoVersion":"","Os":"","Arch":""}}

cli/command/system/version.go

@@ -11,7 +11,9 @@ import (
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/cli/cli/command/completion"
+	"github.com/docker/cli/cli/command/formatter"
 	"github.com/docker/cli/cli/command/formatter/tabwriter"
+	flagsHelper "github.com/docker/cli/cli/flags"
 	"github.com/docker/cli/cli/version"
 	"github.com/docker/cli/templates"
 	"github.com/docker/docker/api/types"
@@ -101,9 +103,7 @@ func NewVersionCommand(dockerCli command.Cli) *cobra.Command {
 		ValidArgsFunction: completion.NoComplete,
 	}
 
-	flags := cmd.Flags()
+	cmd.Flags().StringVarP(&opts.format, "format", "f", "", flagsHelper.InspectFormatHelp)
-	flags.StringVarP(&opts.format, "format", "f", "", "Format the output using the given Go template")
-
 	return cmd
 }
 
@@ -194,8 +194,11 @@ func prettyPrintVersion(dockerCli command.Cli, vd versionInfo, tmpl *template.Te
 }
 
 func newVersionTemplate(templateFormat string) (*template.Template, error) {
-	if templateFormat == "" {
+	switch templateFormat {
+	case "":
 		templateFormat = defaultVersionTemplate
+	case formatter.JSONFormatKey:
+		templateFormat = formatter.JSONFormat
 	}
 	tmpl := templates.New("version").Funcs(template.FuncMap{"getDetailsOrder": getDetailsOrder})
 	tmpl, err := tmpl.Parse(templateFormat)

cli/command/system/version_test.go

@@ -6,12 +6,11 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/docker/cli/internal/test"
+	"github.com/docker/docker/api/types"
 	"gotest.tools/v3/assert"
 	is "gotest.tools/v3/assert/cmp"
 	"gotest.tools/v3/golden"
-
-	"github.com/docker/cli/internal/test"
-	"github.com/docker/docker/api/types"
 )
 
 func TestVersionWithoutServer(t *testing.T) {
@@ -30,7 +29,7 @@ func TestVersionWithoutServer(t *testing.T) {
 	assert.Assert(t, !strings.Contains(out, "Server:"), "actual: %s", out)
 }
 
-func TestVersionAlign(t *testing.T) {
+func TestVersionFormat(t *testing.T) {
 	vi := versionInfo{
 		Client: clientVersion{
 			Version:           "18.99.5-ce",
@@ -104,10 +103,28 @@ func TestVersionAlign(t *testing.T) {
 		},
 	})
 
-	cli := test.NewFakeCli(&fakeClient{})
+	t.Run("default", func(t *testing.T) {
-	tmpl, err := newVersionTemplate("")
+		cli := test.NewFakeCli(&fakeClient{})
-	assert.NilError(t, err)
+		tmpl, err := newVersionTemplate("")
-	assert.NilError(t, prettyPrintVersion(cli, vi, tmpl))
+		assert.NilError(t, err)
-	assert.Check(t, golden.String(cli.OutBuffer().String(), "docker-client-version.golden"))
+		assert.NilError(t, prettyPrintVersion(cli, vi, tmpl))
-	assert.Check(t, is.Equal("", cli.ErrBuffer().String()))
+		assert.Check(t, golden.String(cli.OutBuffer().String(), "docker-client-version.golden"))
+		assert.Check(t, is.Equal("", cli.ErrBuffer().String()))
+	})
+	t.Run("json", func(t *testing.T) {
+		cli := test.NewFakeCli(&fakeClient{})
+		tmpl, err := newVersionTemplate("json")
+		assert.NilError(t, err)
+		assert.NilError(t, prettyPrintVersion(cli, vi, tmpl))
+		assert.Check(t, golden.String(cli.OutBuffer().String(), "docker-client-version.json.golden"))
+		assert.Check(t, is.Equal("", cli.ErrBuffer().String()))
+	})
+	t.Run("json template", func(t *testing.T) {
+		cli := test.NewFakeCli(&fakeClient{})
+		tmpl, err := newVersionTemplate("{{json .}}")
+		assert.NilError(t, err)
+		assert.NilError(t, prettyPrintVersion(cli, vi, tmpl))
+		assert.Check(t, golden.String(cli.OutBuffer().String(), "docker-client-version.json.golden"))
+		assert.Check(t, is.Equal("", cli.ErrBuffer().String()))
+	})
 }

docs/reference/commandline/version.md

@@ -5,9 +5,9 @@ Show the Docker version information
 
 ### Options
 
-| Name                                   | Type     | Default | Description                                   |
+| Name                                   | Type     | Default | Description                                                                                                                                                                                                                                                        |
-|:---------------------------------------|:---------|:--------|:----------------------------------------------|
+|:---------------------------------------|:---------|:--------|:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| [`-f`](#format), [`--format`](#format) | `string` |         | Format the output using the given Go template |
+| [`-f`](#format), [`--format`](#format) | `string` |         | Format output using a custom template:<br>'json':             Print in JSON format<br>'TEMPLATE':         Print output using the given Go template.<br>Refer to https://docs.docker.com/go/formatting/ for more information about formatting output with templates |
 
 
 <!---MARKER_GEN_END-->