Add specific "json" value to format flag with inspect commands to output json, as empty flag does.

Added tests on that new behavior.

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

cli/command/inspect/inspector.go

@@ -38,7 +38,7 @@ func NewTemplateInspector(outputStream io.Writer, tmpl *template.Template) Inspe
 // NewTemplateInspectorFromString creates a new TemplateInspector from a string
 // which is compiled into a template.
 func NewTemplateInspectorFromString(out io.Writer, tmplStr string) (Inspector, error) {
-	if tmplStr == "" {
+	if tmplStr == "" || tmplStr == "json" {
 		return NewIndentedInspector(out), nil
 	}
 

cli/command/inspect/inspector_test.go

@@ -257,3 +257,57 @@ func TestTemplateInspectorRawFallbackNumber(t *testing.T) {
 		b.Reset()
 	}
 }
+
+func TestNewTemplateInspectorFromString(t *testing.T) {
+	testCases := []struct {
+		name     string
+		template string
+		expected string
+	}{
+		{
+			name:     "empty template outputs json by default",
+			template: "",
+			expected: `[
+    {
+        "Name": "test"
+    }
+]
+`,
+		},
+		{
+			name:     "json specific value outputs json",
+			template: "json",
+			expected: `[
+    {
+        "Name": "test"
+    }
+]
+`,
+		},
+		{
+			name:     "template is applied",
+			template: "{{.Name}}",
+			expected: "test\n",
+		},
+	}
+	value := struct {
+		Name string
+	}{
+		"test",
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			b := new(bytes.Buffer)
+			i, err := NewTemplateInspectorFromString(b, tc.template)
+			assert.NilError(t, err)
+
+			err = i.Inspect(value, nil)
+			assert.NilError(t, err)
+
+			err = i.Flush()
+			assert.NilError(t, err)
+
+			assert.Equal(t, b.String(), tc.expected)
+		})
+	}
+}