Added "json" as specific value for --format flag in list commands, as an alias to `{{json .}}`

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/formatter/formatter.go

@@ -16,8 +16,10 @@ const (
 	TableFormatKey  = "table"
 	RawFormatKey    = "raw"
 	PrettyFormatKey = "pretty"
+	JSONFormatKey   = "json"
 
 	DefaultQuietFormat = "{{.ID}}"
+	jsonFormat         = "{{json .}}"
 )
 
 // Format is the format string rendered using the Context
@@ -28,6 +30,11 @@ func (f Format) IsTable() bool {
 	return strings.HasPrefix(string(f), TableFormatKey)
 }
 
+// IsJSON returns true if the format is the json format
+func (f Format) IsJSON() bool {
+	return string(f) == JSONFormatKey
+}
+
 // Contains returns true if the format contains the substring
 func (f Format) Contains(sub string) bool {
 	return strings.Contains(string(f), sub)
@@ -50,10 +57,12 @@ type Context struct {
 
 func (c *Context) preFormat() {
 	c.finalFormat = string(c.Format)
-
 	// TODO: handle this in the Format type
-	if c.Format.IsTable() {
+	switch {
+	case c.Format.IsTable():
 		c.finalFormat = c.finalFormat[len(TableFormatKey):]
+	case c.Format.IsJSON():
+		c.finalFormat = jsonFormat
 	}
 
 	c.finalFormat = strings.Trim(c.finalFormat, " ")

cli/command/formatter/formatter_test.go

@@ -0,0 +1,68 @@
+package formatter
+
+import (
+	"bytes"
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestFormat(t *testing.T) {
+	f := Format("json")
+	assert.Assert(t, f.IsJSON())
+	assert.Assert(t, !f.IsTable())
+
+	f = Format("table")
+	assert.Assert(t, !f.IsJSON())
+	assert.Assert(t, f.IsTable())
+
+	f = Format("other")
+	assert.Assert(t, !f.IsJSON())
+	assert.Assert(t, !f.IsTable())
+}
+
+type fakeSubContext struct {
+	Name string
+}
+
+func (f fakeSubContext) FullHeader() interface{} {
+	return map[string]string{"Name": "NAME"}
+}
+
+func TestContext(t *testing.T) {
+	testCases := []struct {
+		name     string
+		format   string
+		expected string
+	}{
+		{
+			name:   "json format",
+			format: JSONFormatKey,
+			expected: `{"Name":"test"}
+`,
+		},
+		{
+			name:   "table format",
+			format: `table {{.Name}}`,
+			expected: `NAME
+test
+`,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			buf := bytes.NewBuffer(nil)
+			ctx := Context{
+				Format: Format(tc.format),
+				Output: buf,
+			}
+			subContext := fakeSubContext{Name: "test"}
+			subFormat := func(f func(sub SubContext) error) error {
+				return f(subContext)
+			}
+			err := ctx.Write(&subContext, subFormat)
+			assert.NilError(t, err)
+			assert.Equal(t, buf.String(), tc.expected)
+		})
+	}
+}