Fix unexpanded value checks.

Capture unexpanded value for later checks. Handles issue with
determining value when keyword aliases may have been used.

Author: davidlehn

lib/expand.js

@@ -406,6 +406,7 @@ async function _expandObject({
 }) {
   const keys = Object.keys(element).sort();
   const nests = [];
+  let unexpandedValue;
   for(const key of keys) {
     let value = element[key];
     let expandedValue;
@@ -513,6 +514,9 @@ async function _expandObject({
     }
 
     if(expandedProperty === '@value') {
+      // capture value for later
+      // "colliding keywords" check prevents this from being set twice
+      unexpandedValue = value;
       _addValue(
         expandedParent, '@value', value, {propertyIsArray: options.isFrame});
       continue;
@@ -770,16 +774,16 @@ async function _expandObject({
   // @value must not be an object or an array (unless framing) or if @type is
   // @json
   if('@value' in expandedParent) {
-    const value = expandedParent['@value'];
     if(expandedParent['@type'] === '@json' && _processingMode(activeCtx, 1.1)) {
       // allow any value, to be verified when the object is fully expanded and
       // the @type is @json.
-    } else if((_isObject(value) || _isArray(value)) && !options.isFrame) {
+    } else if((_isObject(unexpandedValue) || _isArray(unexpandedValue)) &&
+      !options.isFrame) {
       throw new JsonLdError(
         'Invalid JSON-LD syntax; "@value" value must not be an ' +
         'object or an array.',
         'jsonld.SyntaxError',
-        {code: 'invalid value object value', value});
+        {code: 'invalid value object value', value: unexpandedValue});
     }
   }