Introduce explicity resource management to Transaction (#1155)

bigmontz · web-flow · commit f58a089fd1f1 · 2023-10-30T16:36:14.000+01:00
This is a TC39 [proposal](https://github.com/tc39/proposal-explicit-resource-management) which is already implemented in Typescript 5.2, core-js, babel and other polyfill tools. This feature enables the user begin a transaction with the `await using` keywords and then do not have to close the resource afterwards, since this resources will be closed after leaving the block which were created at. Transaction will be closed using with the same behaviour as `Transaction.close` calls. So, the transaction will be rollback if still open. _Note: For better usage in cluster environments, you should use `executeRead` and `executeWrite` for handling retries._ Usage example: ```typescript await using tx = session.beginTransaction() await tx.run('CREATE (p:Person { name:$name }) RETURN p', { name }).summary() await tx.commit() ```
diff --git a/packages/core/src/transaction.ts b/packages/core/src/transaction.ts
@@ -291,6 +291,12 @@ class Transaction {
     }
   }
 
+  // eslint-disable-next-line
+  // @ts-ignore
+  [Symbol.asyncDispose] (): Promise<void> {
+    return this.close()
+  }
+
   _onErrorCallback (error: Error): Promise<Connection | null> {
     // error will be "acknowledged" by sending a RESET message
     // database will then forget about this transaction and cleanup all corresponding resources
diff --git a/packages/neo4j-driver-deno/lib/core/transaction.ts b/packages/neo4j-driver-deno/lib/core/transaction.ts
@@ -291,6 +291,12 @@ class Transaction {
     }
   }
 
+  // eslint-disable-next-line
+  // @ts-ignore
+  [Symbol.asyncDispose] (): Promise<void> {
+    return this.close()
+  }
+
   _onErrorCallback (error: Error): Promise<Connection | null> {
     // error will be "acknowledged" by sending a RESET message
     // database will then forget about this transaction and cleanup all corresponding resources
diff --git a/packages/neo4j-driver-deno/test/neo4j.test.ts b/packages/neo4j-driver-deno/test/neo4j.test.ts
@@ -17,6 +17,8 @@
  * limitations under the License.
  */
 import neo4j from '../lib/mod.ts'
+//@ts-ignore
+import { assertEquals } from "https://deno.land/std@0.182.0/testing/asserts.ts";
 
 const env = Deno.env.toObject()
 
@@ -42,3 +44,42 @@ Deno.test('driver.session should be able to use explicity resource management',
 
   await session.executeRead(tx => "RETURN 1")
 })
+
+
+// Deno will fail with resource leaks
+Deno.test('session.beginTransaction should rollback the transaction if not committed', async () => {
+  await using driver = neo4j.driver(uri, authToken)
+  await using session = driver.session()
+  const name = "Must Be Conor"
+
+
+  {
+    await using tx = session.beginTransaction()
+    await tx.run('CREATE (p:Person { name:$name }) RETURN p', { name }).summary()
+  }
+
+  const { records } = await driver.executeQuery('MATCH (p:Person { name:$name }) RETURN p', { name })
+  assertEquals(records.length, 0) 
+})
+
+
+// Deno will fail with resource leaks
+Deno.test('session.beginTransaction should noop if resource committed', async () => {
+  await using driver = neo4j.driver(uri, authToken)
+  try {
+    await using session = driver.session()
+    const name = "Must Be Conor"
+  
+    {
+      await using tx = session.beginTransaction()
+      await tx.run('CREATE (p:Person { name:$name }) RETURN p', { name }).summary()
+      await tx.commit()
+    }
+  
+    const { records } = await driver.executeQuery('MATCH (p:Person { name:$name }) RETURN p', { name })
+    assertEquals(records.length, 1) 
+  } finally {
+    // cleaning up
+    await driver.executeQuery('MATCH (p:Person { name:$name }) DELETE(p)', { name })
+  }
+})

Original file line number	Diff line number	Diff line change
`@@ -291,6 +291,12 @@ class Transaction {`
`291`	`291`	`}`
`292`	`292`	`}`
`293`	`293`
	`294`	`+ // eslint-disable-next-line`
	`295`	`+ // @ts-ignore`
	`296`	`+ [Symbol.asyncDispose] (): Promise<void> {`
	`297`	`+ return this.close()`
	`298`	`+ }`
	`299`	`+`
`294`	`300`	`_onErrorCallback (error: Error): Promise<Connection \| null> {`
`295`	`301`	`// error will be "acknowledged" by sending a RESET message`
`296`	`302`	`// database will then forget about this transaction and cleanup all corresponding resources`