Add inverse transform

Author: GeertWille

README.md

@@ -387,6 +387,7 @@ For more control over an attribute's behavior, you can specify an object as the
 | prefix  | `string` | `string` | A prefix to be added to an attribute when saved to DynamoDB. This prefix will be removed when parsing the data. |
 | suffix  | `string` | `string` | A suffix to be added to an attribute when saved to DynamoDB. This suffix will be removed when parsing the data. |
 | transform  | `function` | all | A function that transforms the input before sending to DynamoDB. This accepts two arguments, the value passed and an object containing the data from other attributes. |
+| inverseTransform  | `function` | all | A function that transforms the input before sending to the parser. This accepts two arguments, the value passed and an object containing the data from other attributes. |
 | partitionKey  | `boolean` or `string` | all | Flags an attribute as the 'partitionKey' for this Entity. If set to `true`, it will be mapped to the Table's `partitionKey`. If set to the name of an **index** defined on the Table, it will be mapped to the secondary index's `partitionKey` |
 | sortKey  | `boolean` or `string` | all | Flags an attribute as the 'sortKey' for this Entity. If set to `true`, it will be mapped to the Table's `sortKey`. If set to the name of an **index** defined on the Table, it will be mapped to the secondary index's `sortKey` |
 

__tests__/entities/test-entity.js

@@ -27,6 +27,7 @@ module.exports = {
     test_string_set_type_coerce: { type: 'set', setType: 'string', coerce: true },
     test_number_set_type_coerce: { type: 'set', setType: 'number', coerce: true },
     test_binary: { type: 'binary' },
-    simple_string: 'string'
+    simple_string: 'string',
+    inverse_transformed_simple_string: { type: 'string', inverseTransform: (input) => input.toUpperCase() }
   }
 }

__tests__/entity-creation.unit.test.js

@@ -565,5 +565,35 @@ describe('Entity creation', ()=> {
 
   }) // creates attribute with transformations
 
+  it('creates an attribute with a inverseTransformation function', async () => {
+    // Create basic table
+    const TestTable = new Table({
+      name: 'test-table',
+      partitionKey: 'pk',
+      sortKey: 'sk',
+      DocumentClient
+    })
 
-})
+    // Create basic entity
+    const TestEntity = new Entity({
+      name: 'TestEnt',
+      attributes: {
+        pk: { partitionKey: true, inverseTransform: (val) => val.toUpperCase(), default: 'pkDef' },
+        test: { 
+          inverseTransform: (val,data) => {
+            return val.toUpperCase()
+          },
+          default: () => 'defaultVal',
+        },
+        sk: { type: 'string', sortKey: true },
+        testx: ['sk',0],
+        testy: ['sk',1, { 
+          default: () => 'testDefaultX', 
+          inverseTransform: (val) => { return '__'+val.toUpperCase() }
+        }]
+      },
+      table: TestTable,
+      timestamps: false
+    })
+  })
+})

__tests__/entity.parse.unit.test.js

@@ -21,12 +21,13 @@ const TestTable = new Table({
 describe('parse',()=>{
 
   it('parses single item', ()=>{
-    let item = TestEntity.parse({ pk: '[email protected]', sk: 'email', test_string: 'test', _et: 'TestEntity' })
+    let item = TestEntity.parse({ pk: '[email protected]', sk: 'email', test_string: 'test', inverse_transformed_simple_string: 'transformed' , _et: 'TestEntity' })
     expect(item).toEqual({
       email: '[email protected]',
       test_type: 'email',
       test_string: 'test',
-      entity: 'TestEntity'
+      entity: 'TestEntity',
+      inverse_transformed_simple_string: 'TRANSFORMED'
     })
   })
 
@@ -40,19 +41,21 @@ describe('parse',()=>{
 
   it('parses multiple items', ()=>{
     let items = TestEntity.parse([
-      { pk: '[email protected]', sk: 'email', test_string: 'test' },
-      { pk: '[email protected]', sk: 'email2', test_string: 'test2' }
+      { pk: '[email protected]', sk: 'email', test_string: 'test', inverse_transformed_simple_string: 'transformed' },
+      { pk: '[email protected]', sk: 'email2', test_string: 'test2', inverse_transformed_simple_string: 'transformed' }
     ])
     expect(items).toEqual([
       {
         email: '[email protected]',
         test_type: 'email',
-        test_string: 'test'
+        test_string: 'test',
+        inverse_transformed_simple_string: 'TRANSFORMED'
       },
       {
         email: '[email protected]',
         test_type: 'email2',
-        test_string: 'test2'
+        test_string: 'test2',
+        inverse_transformed_simple_string: 'TRANSFORMED'
       }
     ])
   })

lib/formatItem.js

@@ -36,18 +36,21 @@ module.exports = (DocumentClient) => (attributes,linked,item,include=[]) => {
     if ((attributes[field] && attributes[field].hidden) || (include.length > 0 && !include.includes(field))) return acc
     // Extract values from sets
     if (attributes[field] && attributes[field].type === 'set' && Array.isArray(item[field].values)) { item[field] = item[field].values } 
+
+    const fieldValue = attributes[field] && (attributes[field].prefix || attributes[field].suffix)
+      ? item[field]
+        .replace(new RegExp(`^${escapeRegExp(attributes[field].prefix)}`),'')
+        .replace(new RegExp(`${escapeRegExp(attributes[field].suffix)}$`),'')
+      : item[field]
+
+    const transformedValue = attributes[field] && attributes[field].inverseTransform ? attributes[field].inverseTransform(fieldValue, item) : fieldValue
+
     return Object.assign(acc,{
-      [(attributes[field] && attributes[field].alias) || field]: (
-        attributes[field] && (attributes[field].prefix || attributes[field].suffix)
-          ? item[field]
-            .replace(new RegExp(`^${escapeRegExp(attributes[field].prefix)}`),'')
-            .replace(new RegExp(`${escapeRegExp(attributes[field].suffix)}$`),'')
-          : item[field]
-      )
+      [(attributes[field] && attributes[field].alias) || field]: transformedValue
     })
   },{})
 }
 
 function escapeRegExp(text) {
   return text ? text.replace(/[-[\]{}()*+?.,\\^$|#]/g, '\\$&') : ''
-}
+}

lib/parseMapping.js

@@ -24,6 +24,9 @@ module.exports = (field,config,track) => {
       case 'transform':
         if (typeof config[prop] !== 'function') error(`'${prop}' must be a function`)
         break
+      case 'inverseTransform':
+        if (typeof config[prop] !== 'function') error(`'${prop}' must be a function`)
+        break
       case 'coerce':
       case 'onUpdate':
       case 'hidden':