tpl: Extend Jsonify to support optional indent parameter

Fixes gohugoio#5040

tpl/encoding/encoding.go

@@ -17,6 +17,7 @@ package encoding
 import (
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"html/template"
 
 	"github.com/spf13/cast"
@@ -51,9 +52,32 @@ func (ns *Namespace) Base64Encode(content interface{}) (string, error) {
 	return base64.StdEncoding.EncodeToString([]byte(conv)), nil
 }
 
-// Jsonify encodes a given object to JSON.
-func (ns *Namespace) Jsonify(v interface{}) (template.HTML, error) {
-	b, err := json.Marshal(v)
+// Jsonify encodes a given object to JSON.  To pretty print the JSON, pass an
+// optional first argument of the indent string, such as "  ".
+func (ns *Namespace) Jsonify(args ...interface{}) (template.HTML, error) {
+	var (
+		b   []byte
+		err error
+	)
+
+	switch len(args) {
+	case 0:
+		return "", nil
+	case 1:
+		b, err = json.Marshal(args[0])
+	case 2:
+		var indent string
+
+		indent, err = cast.ToStringE(args[0])
+		if err != nil {
+			break
+		}
+
+		b, err = json.MarshalIndent(args[1], "", indent)
+	default:
+		err = errors.New("too many arguments to jsonify")
+	}
+
 	if err != nil {
 		return "", err
 	}

tpl/encoding/encoding_test.go

@@ -83,17 +83,22 @@ func TestJsonify(t *testing.T) {
 	ns := New()
 
 	for _, test := range []struct {
+		indent []interface{}
 		v      interface{}
 		expect interface{}
 	}{
-		{[]string{"a", "b"}, template.HTML(`["a","b"]`)},
-		{tstNoStringer{}, template.HTML("{}")},
-		{nil, template.HTML("null")},
+		{nil, []string{"a", "b"}, template.HTML(`["a","b"]`)},
+		{[]interface{}{"  "}, []string{"a", "b"}, template.HTML("[\n  \"a\",\n  \"b\"\n]")},
+		{nil, tstNoStringer{}, template.HTML("{}")},
+		{nil, nil, template.HTML("null")},
 		// errors
-		{math.NaN(), false},
+		{nil, math.NaN(), false},
+		{[]interface{}{tstNoStringer{}}, []string{"a", "b"}, false},
 	} {
 
-		result, err := ns.Jsonify(test.v)
+		args := append(test.indent, test.v)
+
+		result, err := ns.Jsonify(args...)
 
 		if b, ok := test.expect.(bool); ok && !b {
 			c.Assert(err, qt.Not(qt.IsNil))

tpl/encoding/init.go

@@ -48,11 +48,11 @@ func init() {
 			[]string{"jsonify"},
 			[][2]string{
 				{`{{ (slice "A" "B" "C") | jsonify }}`, `["A","B","C"]`},
+				{`{{ (slice "A" "B" "C") | jsonify "  "}}`, "[\n  \"A\",\n  \"B\",\n  \"C\"\n]"},
 			},
 		)
 
 		return ns
-
 	}
 
 	internal.AddTemplateFuncsNamespace(f)