fix dynamodb-toolbox#51 by checking for empty ExpressionAttributeValues objects

Author: jeremydaly

classes/Entity.js

@@ -18,7 +18,7 @@ const parseConditions = require('../lib/expressionBuilder')
 const parseProjections = require('../lib/projectionBuilder')
 
 // Import error handlers
-const { error, transformAttr } = require('../lib/utils')
+const { error, transformAttr, isEmpty } = require('../lib/utils')
 
 // Declare Entity class
 class Entity {
@@ -346,7 +346,7 @@ class Entity {
         Key: getKey(this.DocumentClient)(data,schema.attributes,schema.keys.partitionKey,schema.keys.sortKey)
       },
       ExpressionAttributeNames ? { ExpressionAttributeNames } : null,
-      ExpressionAttributeValues ? { ExpressionAttributeValues } : null,
+      !isEmpty(ExpressionAttributeValues) ? { ExpressionAttributeValues } : null,
       ConditionExpression ? { ConditionExpression } : null,
       capacity ? { ReturnConsumedCapacity: capacity.toUpperCase() } : null,
       metrics ? { ReturnItemCollectionMetrics: metrics.toUpperCase() } : null,
@@ -657,7 +657,7 @@ class Entity {
         ExpressionAttributeNames: Object.assign(names,ExpressionAttributeNames)
       },
       typeof params === 'object' ? params : {},
-      Object.keys(ExpressionAttributeValues).length > 0 ? { ExpressionAttributeValues } : {},
+      !isEmpty(ExpressionAttributeValues) ? { ExpressionAttributeValues } : {},
       ConditionExpression ? { ConditionExpression } : {},
       capacity ? { ReturnConsumedCapacity: capacity.toUpperCase() } : null,
       metrics ? { ReturnItemCollectionMetrics: metrics.toUpperCase() } : null,
@@ -800,7 +800,7 @@ class Entity {
         },{})
       },
       ExpressionAttributeNames ? { ExpressionAttributeNames } : null,
-      ExpressionAttributeValues ? { ExpressionAttributeValues } : null,
+      !isEmpty(ExpressionAttributeValues) ? { ExpressionAttributeValues } : null,
       ConditionExpression ? { ConditionExpression } : null,
       capacity ? { ReturnConsumedCapacity: capacity.toUpperCase() } : null,
       metrics ? { ReturnItemCollectionMetrics: metrics.toUpperCase() } : null,

lib/utils.js

@@ -21,6 +21,9 @@ module.exports.toBool = val =>
 // has value shortcut
 module.exports.hasValue = val => val !== undefined && val !== null
 
+// isEmpty object shortcut
+module.exports.isEmpty = val => val === undefined || (typeof val === 'object' && Object.keys(val).length === 0)
+
 // Inline error handler
 const error = err => { throw new Error(err) }
 module.exports.error = error
@@ -39,7 +42,7 @@ module.exports.keyTypeError = field => {
 }
 
 
-// Tranform atribute values
+// Transform atribute values
 module.exports.transformAttr = (mapping,value,data) => {  
   value = mapping.transform ? mapping.transform(value,data) : value
   return mapping.prefix || mapping.suffix ?