unpack outer wrapper in $string()

Signed-off-by: andrew-coleman <andrew_coleman@uk.ibm.com>

Author: andrew-coleman

src/functions.js

@@ -126,6 +126,9 @@ const functions = (() => {
             };
         } else {
             var space = prettify ? 2 : 0;
+            if(Array.isArray(arg) && arg.outerWrapper) {
+                arg = arg[0];
+            }
             str = JSON.stringify(arg, function (key, val) {
                 return (typeof val !== 'undefined' && val !== null && val.toPrecision && isNumeric(val)) ? Number(val.toPrecision(15)) :
                     (val && isFunction(val)) ? '' : val;

test/test-suite/groups/function-string/case029.json

@@ -0,0 +1,6 @@
+{
+    "expr": "$string()",
+    "data": [4, true],
+    "bindings": {},
+    "result": "[4,true]"
+}