tpl: Extend Jsonify to support options map

Add support for prefix and indent options used by json.MarshalIndent
from the Go stdlib.

tpl/encoding/encoding.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
+// Copyright 2020 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -52,8 +52,11 @@ func (ns *Namespace) Base64Encode(content interface{}) (string, error) {
 	return base64.StdEncoding.EncodeToString([]byte(conv)), nil
 }
 
-// Jsonify encodes a given object to JSON.  To pretty print the JSON, pass an
-// optional first argument of the indent string, such as "  ".
+// Jsonify encodes a given object to JSON.  To pretty print the JSON, pass a map
+// or dictionary of options as the first argument.  Supported options are
+// "prefix" and "indent".  Each JSON element in the output will begin on a new
+// line beginning with prefix followed by one or more copies of indent according
+// to the indentation nesting.
 func (ns *Namespace) Jsonify(args ...interface{}) (template.HTML, error) {
 	var (
 		b   []byte
@@ -66,14 +69,14 @@ func (ns *Namespace) Jsonify(args ...interface{}) (template.HTML, error) {
 	case 1:
 		b, err = json.Marshal(args[0])
 	case 2:
-		var indent string
+		var opts map[string]string
 
-		indent, err = cast.ToStringE(args[0])
+		opts, err = cast.ToStringMapStringE(args[0])
 		if err != nil {
 			break
 		}
 
-		b, err = json.MarshalIndent(args[1], "", indent)
+		b, err = json.MarshalIndent(args[1], opts["prefix"], opts["indent"])
 	default:
 		err = errors.New("too many arguments to jsonify")
 	}

tpl/encoding/encoding_test.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
+// Copyright 2020 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -83,20 +83,27 @@ func TestJsonify(t *testing.T) {
 	ns := New()
 
 	for _, test := range []struct {
-		indent []interface{}
+		opts   interface{}
 		v      interface{}
 		expect interface{}
 	}{
 		{nil, []string{"a", "b"}, template.HTML(`["a","b"]`)},
-		{[]interface{}{"  "}, []string{"a", "b"}, template.HTML("[\n  \"a\",\n  \"b\"\n]")},
+		{map[string]string{"indent": "<i>"}, []string{"a", "b"}, template.HTML("[\n<i>\"a\",\n<i>\"b\"\n]")},
+		{map[string]string{"prefix": "<p>"}, []string{"a", "b"}, template.HTML("[\n<p>\"a\",\n<p>\"b\"\n<p>]")},
+		{map[string]string{"prefix": "<p>", "indent": "<i>"}, []string{"a", "b"}, template.HTML("[\n<p><i>\"a\",\n<p><i>\"b\"\n<p>]")},
 		{nil, tstNoStringer{}, template.HTML("{}")},
 		{nil, nil, template.HTML("null")},
 		// errors
 		{nil, math.NaN(), false},
-		{[]interface{}{tstNoStringer{}}, []string{"a", "b"}, false},
+		{tstNoStringer{}, []string{"a", "b"}, false},
 	} {
+		args := []interface{}{}
 
-		args := append(test.indent, test.v)
+		if test.opts != nil {
+			args = append(args, test.opts)
+		}
+
+		args = append(args, test.v)
 
 		result, err := ns.Jsonify(args...)
 

tpl/encoding/init.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
+// Copyright 2020 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -48,7 +48,7 @@ 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]"},
+				{`{{ (slice "A" "B" "C") | jsonify (dict "indent" "  ") }}`, "[\n  \"A\",\n  \"B\",\n  \"C\"\n]"},
 			},
 		)