some fixes from code review

Author: brysgo

lib/helpers.js

@@ -4,17 +4,15 @@ async function resolveAuthLevel(schema, options, doc) {
   // Look into options the options and try to find authLevels. Always prefer to take
   // authLevels from the direct authLevel option as opposed to the computed
   // ones from getAuthLevel in the schema object.
-  let authLevelsIn = [];
+  let authLevels = [];
   if (options) {
     if (options.authLevel) {
-      authLevelsIn = options.authLevel;
+      authLevels = _.castArray(options.authLevel);
     } else if (typeof schema.getAuthLevel === 'function') {
-      authLevelsIn = schema.getAuthLevel(options.authPayload, doc);
+      authLevels = _.castArray(await schema.getAuthLevel(options.authPayload, doc));
     }
   }
 
-  const authLevels = _.castArray(await Promise.resolve(authLevelsIn));
-
   // Add `defaults` to the list of levels since you should always be able to do what's specified
   // in defaults.
   authLevels.push('defaults');
@@ -117,18 +115,18 @@ async function sanitizeDocument(schema, options, doc) {
 async function sanitizeDocumentList(schema, options, docs) {
   const multi = _.isArrayLike(docs);
   const docList = _.castArray(docs);
+  const sanitizeAndAddOptions = (doc) => {
+    const upgradedOptions = _.isEmpty(schema.pathsWithPermissionedSchemas)
+      ? options
+      : _.merge({}, options, { authPayload: { originalDoc: doc } });
+    return sanitizeDocument(schema, upgradedOptions, doc);
+  };
 
-  const filteredResult = _.chain(await Promise.all(_.map(docList, async (doc) => {
-      const upgradedOptions = _.isEmpty(schema.pathsWithPermissionedSchemas)
-        ? options
-        : _.merge({}, options, { authPayload: { originalDoc: doc } });
-
-      return await sanitizeDocument(schema, upgradedOptions, doc);
-    })))
-    .filter(docList)
-    .value();
+  const filteredResult = (
+    await Promise.all(docList.map(sanitizeAndAddOptions))
+  ).filter(doc => !doc);
 
-  return multi ? Promise.all(filteredResult) : filteredResult[0];
+  return multi ? (filteredResult) : filteredResult[0];
 }
 
 function getUpdatePaths(updates) {