fix string type checking and circular reference, working on #81

src/render.js

@@ -1,6 +1,7 @@
 const Syntax = require('./syntax.js')
 const mapSeries = require('./util/promise.js').mapSeries
 const RenderBreakError = require('./util/error.js').RenderBreakError
+const _ = require('./util/underscore.js')
 const RenderError = require('./util/error.js').RenderError
 const assert = require('./util/assert.js')
 
@@ -27,9 +28,7 @@ var render = {
         return this.renderTag(template, scope)
           .then(partial => partial === undefined ? '' : partial)
       } else if (template.type === 'value') {
-        return Promise.resolve()
-          .then(() => this.evalValue(template, scope))
-          .then(partial => partial === undefined ? '' : stringify(partial))
+        return this.renderValue(template, scope)
       } else { // template.type === 'html'
         return Promise.resolve(template.value)
       }
@@ -46,6 +45,12 @@ var render = {
     return template.render(scope)
   },
 
+  renderValue: function (template, scope) {
+    return Promise.resolve()
+      .then(() => this.evalValue(template, scope))
+      .then(partial => partial === undefined ? '' : _.stringify(partial))
+  },
+
   evalValue: function (template, scope) {
     assert(scope, 'unable to evalValue: scope undefined')
     return template.filters.reduce(
@@ -59,9 +64,4 @@ function factory () {
   return instance
 }
 
-function stringify (val) {
-  if (typeof val === 'string') return val
-  return JSON.stringify(val)
-}
-
 module.exports = factory

src/util/underscore.js

@@ -6,7 +6,27 @@ const toStr = Object.prototype.toString
  * @return {Boolean} Returns true if value is a string, else false.
  */
 function isString (value) {
-  return value instanceof String || typeof value === 'string'
+  return toStr.call(value) === '[object String]'
+}
+
+function stringify (value) {
+  if (isString(value)) {
+    return value
+  }
+  if (value && typeof value.to_liquid === 'function') {
+    return value.to_liquid()
+  }
+
+  let cache = []
+  return JSON.stringify(value, (key, value) => {
+    if (isObject(value)) {
+      if (cache.indexOf(value) !== -1) {
+        return
+      }
+      cache.push(value)
+    }
+    return value
+  })
 }
 
 function isNil (value) {
@@ -126,3 +146,4 @@ exports.last = last
 exports.forOwn = forOwn
 exports.assign = assign
 exports.uniq = uniq
+exports.stringify = stringify