Correct return type on call_step()

language_reference.md

@@ -716,7 +716,10 @@ import {
 ### call_step()
 
 ```typescript
-function call_step(func: Function, args: Record<string, unknown>): unknown
+function call_step<T, A extends any[]>(
+  func: (...args: A) => T,
+  arguments: Record<string, unknown>,
+): T
 ```
 
 The `call_step` function outputs a [call step](https://cloud.google.com/workflows/docs/reference/syntax/calls).

samples/sample2.ts

@@ -1,6 +1,6 @@
 // Change the path to 'ts2workflows/types/workflowslib'
 // in projects that use ts2workflows module as a dependency.
-import { sys, time } from '../types/workflowslib'
+import { call_step, sys, time } from '../types/workflowslib'
 import { get_url } from './http_helpers'
 
 function main() {
@@ -12,5 +12,7 @@ function main() {
   // Calling a subworkflow defined in another source file
   const response = get_url('https://visit.dreamland.test/')
 
-  sys.log(response.body as object)
+  // Invoking a function with a call step and named arguments
+  // instead of an ${} expression
+  call_step(sys.log, { severity: 'DEBUG', json: response.body })
 }

types/workflowslib.d.ts

@@ -711,7 +711,7 @@ export declare function retry_policy(
       },
 ): void
 
-export declare function call_step(
-  func: Function,
+export declare function call_step<T, A extends any[]>(
+  func: (...args: A) => T,
   arguments: Record<string, unknown>,
-): unknown
+): T