feat(transact-update): add updateAttribute equivalent to UpdateRequest

Author: mumenthalers

src/dynamo/transactwrite/transact-update.spec.ts

@@ -1,29 +1,27 @@
 import { UpdateModel } from '../../../test/models'
 import { Metadata, metadataForClass } from '../../decorator/metadata'
 import { createKeyAttributes } from '../../mapper'
-import { update } from '../expression/logical-operator/update.function'
+import { update2 } from '../expression/logical-operator/update.function'
 import { getTableName } from '../get-table-name.function'
 import { TransactUpdate } from './transact-update'
 
 describe('TransactUpdate', () => {
   let op: TransactUpdate<UpdateModel>
   let metadata: Metadata<UpdateModel>
+  let now: Date
   beforeEach(() => {
     op = new TransactUpdate(UpdateModel, 'myId')
+    now = new Date()
     metadata = metadataForClass(UpdateModel)
   })
 
-  it('correct transactItem', () => {
-    const now = new Date()
-    op.operations(update<UpdateModel>('lastUpdated').set(now))
-    op.onlyIfAttribute('name').eq('Foo Bar')
-
+  afterEach(() => {
     expect(op.transactItem).toEqual({
       Update: {
         TableName: getTableName(UpdateModel),
         Key: createKeyAttributes(metadata, 'myId'),
 
-        UpdateExpression: 'SET #lastUpdated = :lastUpdated',
+        UpdateExpression: 'SET #lastUpdated = if_not_exists(#lastUpdated, :lastUpdated)',
         ConditionExpression: '#name = :name',
 
         ExpressionAttributeNames: {
@@ -37,4 +35,17 @@ describe('TransactUpdate', () => {
       },
     })
   })
+
+  it('correct transactItem [operations]', () => {
+    op.operations(update2(UpdateModel, 'lastUpdated').set(now, true))
+      .onlyIfAttribute('name')
+      .eq('Foo Bar')
+  })
+
+  it('correct transactItem [updateAttribute]', () => {
+    op.updateAttribute('lastUpdated')
+      .set(now, true)
+      .onlyIfAttribute('name')
+      .eq('Foo Bar')
+  })
 })

src/dynamo/transactwrite/transact-update.ts

@@ -2,7 +2,8 @@ import * as DynamoDB from 'aws-sdk/clients/dynamodb'
 import { createKeyAttributes } from '../../mapper'
 import { ModelConstructor } from '../../model'
 import { prepareAndAddUpdateExpressions } from '../expression/prepare-and-add-update-expressions.function'
-import { UpdateExpressionDefinitionFunction } from '../expression/type'
+import { addUpdate } from '../expression/request-expression-builder'
+import { RequestUpdateFunction, UpdateExpressionDefinitionFunction } from '../expression/type'
 import { TransactBaseOperation } from './transact-base-operation'
 
 export class TransactUpdate<T> extends TransactBaseOperation<T, DynamoDB.Update, TransactUpdate<T>> {
@@ -11,6 +12,10 @@ export class TransactUpdate<T> extends TransactBaseOperation<T, DynamoDB.Update,
     this.params.Key = createKeyAttributes(this.metadata, partitionKey, sortKey)
   }
 
+  updateAttribute<K extends keyof T>(attributePath: K): RequestUpdateFunction<TransactUpdate<T>, T, K> {
+    return addUpdate(attributePath, this, this.metadata)
+  }
+
   operations(...updateDefFns: UpdateExpressionDefinitionFunction[]): TransactUpdate<T> {
     prepareAndAddUpdateExpressions(this.metadata, this.params, updateDefFns)
     return this