Behold the test that catches that branch

Author: omichowdhury

__tests__/formatItem.unit.test.js

@@ -30,8 +30,11 @@ DefaultTable.entities = new Entity({
     linked1: ['sk',0, { save: false }],
     linked2: ['sk',1, { save: false }],
     composite: { type: 'string', alias: 'composite_alias' },
-    linked_alias1: ['composite',0, { save: false, alias: 'linked_alias_one' }],
-    linked_alias2: ['composite',1, { save: false, alias: 'linked_alias_two' }],
+    linked_alias1: ['composite',0, { save: false, alias: 'linked_alias2' }],
+    linked_alias3: ['composite',1, { save: false, alias: 'linked_alias4' }],
+    composite2_alias: { type: 'string', map: 'composite2' },
+    linked_alias5: ['composite2_alias',0, { save: false }],
+    linked_alias7: ['composite2_alias',1, { save: false }],
   }
 })
 
@@ -88,7 +91,12 @@ describe('formatItem', () => {
 
   it('formats item with linked aliased fields', () => {
     let result = formatItem(DocumentClient)(DefaultTable.User.schema.attributes,DefaultTable.User.linked,{ composite: 'test1#test2' })  
-    expect(result).toEqual({ composite_alias: 'test1#test2', linked_alias_one: 'test1', linked_alias_two: 'test2' })
+    expect(result).toEqual({ composite_alias: 'test1#test2', linked_alias2: 'test1', linked_alias4: 'test2' })
+  })
+
+  it('formats item with linked mapped fields', () => {
+    let result = formatItem(DocumentClient)(DefaultTable.User.schema.attributes,DefaultTable.User.linked,{ composite2: 'test1#test2' })  
+    expect(result).toEqual({ composite2_alias: 'test1#test2', linked_alias5: 'test1', linked_alias7: 'test2' })
   })
 
   it('passes through attribute not specified in entity', () => {

lib/formatItem.js

@@ -18,8 +18,9 @@ module.exports = (DocumentClient) => (attributes,linked,item,include=[]) => {
   const validateType = validateTypes(DocumentClient)
 
   return Object.keys(item).reduce((acc,field) => {
-    if (linked[field]) {
-      Object.assign(acc, (linked[field]).reduce((acc,f,i) => {
+    const link = linked[field] || attributes[field] && attributes[field].alias && linked[attributes[field].alias]
+    if (link) {
+      Object.assign(acc, link.reduce((acc,f,i) => {
         if (attributes[f].save || attributes[f].hidden || (include.length > 0 && !include.includes(f))) return acc    
         return Object.assign(acc,{
           [attributes[f].alias || f]: validateType(attributes[f],f,