fix: signature of cds.tx (#544)

Author: daogrady

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 - `ResultHandler` now returns `unknown` instead of `void`, to accommodate asynchronous functions when having `@typescript-eslint/strict-void-return` activated
 - Documentation for `cds.test.axios` mentioning that `@cap-js/cds-test@1` now returns an `axios` facade in absence of `axios`.
 - made `cds.context.locale` optional
+- `cds.tx(ƒ)` now returns the return type of `ƒ`
 
 ### Deprecated
 - `cds.test.chai`, `cds.test.assert` pointing to either `cds.test.expect` or a custom import of `chai`.

apis/services.d.ts

@@ -92,9 +92,9 @@ export class QueryAPI {
   transaction: QueryAPI['tx']
 
   tx: {
-    (fn: (tx: Transaction) => object): Promise<unknown>,
+    <T>(fn: (tx: Transaction) => T): Promise<Awaited<T>>,
     (context?: object): Transaction,
-    (context: object, fn: (tx: Transaction) => object): Promise<unknown>,
+    <T>(context: object, fn: (tx: Transaction) => T): Promise<Awaited<T>>,
   }
 
 }
@@ -519,9 +519,9 @@ export function spawn (options: SpawnOptions, fn: (tx: Transaction) => object):
 * @see [docs](https://cap.cloud.sap/docs/node.js/cds-tx)
 */
 export const tx: {
-  (fn: (tx: Transaction) => object): Promise<any>,
+  <T>(fn: (tx: Transaction) => T): Promise<T>,
   (context?: object): Transaction,
-  (context: object, fn: (tx: Transaction) => object): Promise<any>,
+  <T>(context: object, fn: (tx: Transaction) => T): Promise<T>,
 }
 export const run: Service['run']
 export const foreach: Service['foreach']

test/typescript/apis/project/cds-services.ts

@@ -513,3 +513,9 @@ asrv.on('', (req) => {
 })
 asrv.dispatch('foo')
 asrv.dispatch(['foo', 'bar'])
+
+testType<Promise<number>>(cds.tx((tx) => 42))
+testType<Promise<number>>(cds.tx({}, (tx) => 42))
+testType<Promise<number>>(asrv.tx((tx) => 42))
+testType<Promise<number>>(asrv.tx({}, (tx) => 42))
+testType<number>(await srv.tx(async (tx) => 42))