Use formatter in docker checkpoint ls

Signed-off-by: Boaz Shuster <ripcurld.github@gmail.com>

cli/command/checkpoint/list.go

@@ -1,14 +1,12 @@
 package checkpoint
 
 import (
-	"fmt"
-	"text/tabwriter"
-
 	"golang.org/x/net/context"
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/cli"
 	"github.com/docker/docker/cli/command"
+	"github.com/docker/docker/cli/command/formatter"
 	"github.com/spf13/cobra"
 )
 
@@ -48,15 +46,9 @@ func runList(dockerCli *command.DockerCli, container string, opts listOptions) e
 		return err
 	}
 
-	w := tabwriter.NewWriter(dockerCli.Out(), 20, 1, 3, ' ', 0)
-	fmt.Fprintf(w, "CHECKPOINT NAME")
-	fmt.Fprintf(w, "\n")
-
-	for _, checkpoint := range checkpoints {
-		fmt.Fprintf(w, "%s\t", checkpoint.Name)
-		fmt.Fprint(w, "\n")
+	cpCtx := formatter.Context{
+		Output: dockerCli.Out(),
+		Format: formatter.NewCheckpointFormat(formatter.TableFormatKey),
 	}
-
-	w.Flush()
-	return nil
+	return formatter.CheckpointWrite(cpCtx, checkpoints)
 }

cli/command/formatter/checkpoint.go

@@ -0,0 +1,52 @@
+package formatter
+
+import "github.com/docker/docker/api/types"
+
+const (
+	defaultCheckpointFormat = "table {{.Name}}"
+
+	checkpointNameHeader = "CHECKPOINT NAME"
+)
+
+// NewCheckpointFormat returns a format for use with a checkpoint Context
+func NewCheckpointFormat(source string) Format {
+	switch source {
+	case TableFormatKey:
+		return defaultCheckpointFormat
+	}
+	return Format(source)
+}
+
+// CheckpointWrite writes formatted checkpoints using the Context
+func CheckpointWrite(ctx Context, checkpoints []types.Checkpoint) error {
+	render := func(format func(subContext subContext) error) error {
+		for _, checkpoint := range checkpoints {
+			if err := format(&checkpointContext{c: checkpoint}); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+	return ctx.Write(newCheckpointContext(), render)
+}
+
+type checkpointContext struct {
+	HeaderContext
+	c types.Checkpoint
+}
+
+func newCheckpointContext() *checkpointContext {
+	cpCtx := checkpointContext{}
+	cpCtx.header = volumeHeaderContext{
+		"Name": checkpointNameHeader,
+	}
+	return &cpCtx
+}
+
+func (c *checkpointContext) MarshalJSON() ([]byte, error) {
+	return marshalJSON(c)
+}
+
+func (c *checkpointContext) Name() string {
+	return c.c.Name
+}

cli/command/formatter/checkpoint_test.go

@@ -0,0 +1,55 @@
+package formatter
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/docker/docker/api/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckpointContextFormatWrite(t *testing.T) {
+	cases := []struct {
+		context  Context
+		expected string
+	}{
+		{
+			Context{Format: NewCheckpointFormat(defaultCheckpointFormat)},
+			`CHECKPOINT NAME
+checkpoint-1
+checkpoint-2
+checkpoint-3
+`,
+		},
+		{
+			Context{Format: NewCheckpointFormat("{{.Name}}")},
+			`checkpoint-1
+checkpoint-2
+checkpoint-3
+`,
+		},
+		{
+			Context{Format: NewCheckpointFormat("{{.Name}}:")},
+			`checkpoint-1:
+checkpoint-2:
+checkpoint-3:
+`,
+		},
+	}
+
+	checkpoints := []types.Checkpoint{
+		{"checkpoint-1"},
+		{"checkpoint-2"},
+		{"checkpoint-3"},
+	}
+	for _, testcase := range cases {
+		out := bytes.NewBufferString("")
+		testcase.context.Output = out
+		err := CheckpointWrite(testcase.context, checkpoints)
+		if err != nil {
+			assert.Error(t, err, testcase.expected)
+		} else {
+			assert.Equal(t, out.String(), testcase.expected)
+		}
+	}
+}