Add async dispose to prepared statement

Author: malthe

CHANGES.md

@@ -5,7 +5,8 @@ In next release ...
   type instead of a value.
 
 - Add `[Symbol.asyncDispose]` method to support [Explicit Resource
-  Management](https://github.com/tc39/proposal-explicit-resource-management).
+  Management](https://github.com/tc39/proposal-explicit-resource-management). This
+  works on the client object as well as prepared statements.
 
 - Add `off` method to disable event listening.
 

README.md

@@ -242,6 +242,8 @@ When the prepared statement is no longer needed, it should be closed to release
 ```typescript
 await statement.close();
 ```
+With TypeScript 5.2+ it's also possible to use the `await using` construct which automatically closes the statement at the end of the block.
+
 
 Prepared statements can be used (executed) multiple times, even concurrently.
 

src/client.ts

@@ -96,7 +96,7 @@ export interface Notification {
     payload: string;
 }
 
-export interface PreparedStatement<T = ResultRecord> {
+export interface PreparedStatement<T = ResultRecord> extends AsyncDisposable {
     close: (portal?: string) => Promise<void>;
     execute: (
         values?: any[],
@@ -535,16 +535,19 @@ export class ClientImpl {
                     const types = this.parameterDescriptionQueue.shift();
                     this.cleanupQueue.expect(Cleanup.ParameterDescription);
 
+                    const close = () => {
+                        return new Promise<void>((resolve) => {
+                            this.writer.close(providedNameOrGenerated, 'S');
+                            this.closeHandlerQueue.push(resolve);
+                            this.cleanupQueue.push(Cleanup.Close);
+                            this.writer.flush();
+                            this.send();
+                        });
+                    };
+
                     resolve({
-                        close: () => {
-                            return new Promise<void>((resolve) => {
-                                this.writer.close(providedNameOrGenerated, 'S');
-                                this.closeHandlerQueue.push(resolve);
-                                this.cleanupQueue.push(Cleanup.Close);
-                                this.writer.flush();
-                                this.send();
-                            });
-                        },
+                        [Symbol.asyncDispose]: close,
+                        close,
                         execute: (
                             values?: any[],
                             portal?: string,

test/client.test.ts

@@ -505,6 +505,7 @@ describe('Query', () => {
         deepEqual(result1, { names: ['i'], rows: [[1]], status: 'SELECT 1' });
         const result2 = await stmt.execute([2]);
         deepEqual(result2.rows, [[2]]);
+        deepEqual(stmt.close, stmt[Symbol.asyncDispose]);
         await stmt.close();
     });