make typing for attach and log functions correct (#2238)

CHANGELOG.md

@@ -10,7 +10,8 @@ Please see [CONTRIBUTING.md](https://github.com/cucumber/cucumber/blob/master/CO
 ## [Unreleased]
 ### Fixed
 - Exit correctly when there's a Gherkin parse failure [#2233](https://github.com/cucumber/cucumber-js/pull/2233)
-- Refer to correct example line in JSON formatter ([#2236](https://github.com/cucumber/cucumber-js/pull/2236)) 
+- Refer to correct example line in JSON formatter ([#2236](https://github.com/cucumber/cucumber-js/pull/2236))
+- Expose correct overload types for `this.attach` function ([#2238](https://github.com/cucumber/cucumber-js/pull/2238))
 
 ## [8.11.0] - 2023-02-10
 ### Added

src/runtime/attachment_manager/index.ts

@@ -14,12 +14,23 @@ export interface IAttachment {
 }
 
 export type IAttachFunction = (attachment: IAttachment) => void
-export type ICreateAttachment = (
-  data: Buffer | Readable | string,
-  mediaType?: string,
-  callback?: () => void
-) => void | Promise<void>
-export type ICreateLog = (text: string) => void | Promise<void>
+
+export type ICreateStringAttachment = (data: string, mediaType?: string) => void
+export type ICreateBufferAttachment = (data: Buffer, mediaType: string) => void
+export type ICreateStreamAttachment = (
+  data: Readable,
+  mediaType: string
+) => Promise<void>
+export type ICreateStreamAttachmentWithCallback = (
+  data: Readable,
+  mediaType: string,
+  callback: () => void
+) => void
+export type ICreateAttachment = ICreateStringAttachment &
+  ICreateBufferAttachment &
+  ICreateStreamAttachment &
+  ICreateStreamAttachmentWithCallback
+export type ICreateLog = (text: string) => void
 
 export default class AttachmentManager {
   private readonly onAttachment: IAttachFunction

test-d/attachments.ts

@@ -0,0 +1,21 @@
+import { After } from '../'
+import { expectError, expectType } from 'tsd'
+import { PassThrough } from 'stream'
+
+After(async function () {
+  // log
+  expectType<void>(this.log('things'))
+  // string
+  expectType<void>(this.attach('stuff'))
+  expectType<void>(this.attach('{}', 'application/json'))
+  // buffer
+  expectType<void>(this.attach(Buffer.from('{}'), 'application/json'))
+  // stream
+  expectType<Promise<void>>(this.attach(new PassThrough(), 'application/json'))
+  expectType<void>(
+    this.attach(new PassThrough(), 'application/json', () => undefined)
+  )
+  // buffer and stream flavours must specify media type
+  expectError(this.attach(Buffer.from('{}')))
+  expectError(this.attach(new PassThrough()))
+})