Modified len to be encoding aware

Author: prachi1210

jsone.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 	"unicode"
+	"unicode/utf8"
 
 	i "github.com/taskcluster/json-e/interpreter"
 )
@@ -200,7 +201,7 @@ var builtin = map[string]interface{}{
 	"len": i.WrapFunction(func(v interface{}) (float64, error) {
 		switch val := v.(type) {
 		case string:
-			return float64(len(val)), nil
+			return float64(utf8.RuneCountInString(val)), nil
 		case []interface{}:
 			return float64(len(val)), nil
 		}

specification.yml

@@ -1530,6 +1530,11 @@ context: {key: 'abc'}
 template: {$eval: 'len(key)'}
 result: 3
 ---
+title: len of grinning face unicode character
+context: {key: "\U0001F601"}
+template: {$eval: 'len(key)'}
+result: 1
+---
 title: len (4)
 context: {key: [1,2,3]}
 template: {$eval: 'len("abc")'}

src/builtins.js

@@ -94,7 +94,7 @@ module.exports = (context) => {
 
   define('len', builtins, {
     argumentTests: ['string|array'],
-    invoke: obj => obj.length,
+    invoke: obj => Array.from(obj).length,
   });
 
   define('strip', builtins, {