typescript: type this as IWorld in user functions

CHANGELOG.md

@@ -26,6 +26,7 @@ Please see [CONTRIBUTING.md](https://github.com/cucumber/cucumber/blob/master/CO
 
 ### Fixed
 
+* `this` now explicitly typed in support code functions ([#1667](https://github.com/cucumber/cucumber-js/issues/1667) [#1690](https://github.com/cucumber/cucumber-js/pull/1690))
 * Progress bar formatter now reports total step count correctly ([#1579](https://github.com/cucumber/cucumber-js/issues/1579)
   [#1669](https://github.com/cucumber/cucumber-js/pull/1669))
 * All messages now emitted with project-relative `uri`s

src/support_code_library_builder/types.ts

@@ -22,21 +22,17 @@ export interface ITestStepHookParameter {
   testStepId: string
 }
 
-export type TestCaseHookFunctionWithoutParameter = () => any | Promise<any>
-export type TestCaseHookFunctionWithParameter = (
-  arg: ITestCaseHookParameter
+export type TestCaseHookFunction = (
+  this: any,
+  arg?: ITestCaseHookParameter
 ) => any | Promise<any>
-export type TestCaseHookFunction =
-  | TestCaseHookFunctionWithoutParameter
-  | TestCaseHookFunctionWithParameter
 
-export type TestStepHookFunctionWithoutParameter = () => void
-export type TestStepHookFunctionWithParameter = (
-  arg: ITestStepHookParameter
+export type TestStepHookFunction = (
+  this: any,
+  arg?: ITestStepHookParameter
 ) => void
-export type TestStepHookFunction =
-  | TestStepHookFunctionWithoutParameter
-  | TestStepHookFunctionWithParameter
+
+export type TestStepFunction = (this: any, ...args: any[]) => any | Promise<any>
 
 export interface IDefineStepOptions {
   timeout?: number
@@ -67,11 +63,11 @@ export interface IParameterTypeDefinition<T> {
 
 export interface IDefineSupportCodeMethods {
   defineParameterType: (options: IParameterTypeDefinition<any>) => void
-  defineStep: ((pattern: DefineStepPattern, code: Function) => void) &
+  defineStep: ((pattern: DefineStepPattern, code: TestStepFunction) => void) &
     ((
       pattern: DefineStepPattern,
       options: IDefineStepOptions,
-      code: Function
+      code: TestStepFunction
     ) => void)
   setDefaultTimeout: (milliseconds: number) => void
   setDefinitionFunctionWrapper: (fn: Function) => void
@@ -92,23 +88,23 @@ export interface IDefineSupportCodeMethods {
     ((options: IDefineTestStepHookOptions, code: TestStepHookFunction) => void)
   BeforeAll: ((code: Function) => void) &
     ((options: IDefineTestRunHookOptions, code: Function) => void)
-  Given: ((pattern: DefineStepPattern, code: Function) => void) &
+  Given: ((pattern: DefineStepPattern, code: TestStepFunction) => void) &
     ((
       pattern: DefineStepPattern,
       options: IDefineStepOptions,
-      code: Function
+      code: TestStepFunction
     ) => void)
-  Then: ((pattern: DefineStepPattern, code: Function) => void) &
+  Then: ((pattern: DefineStepPattern, code: TestStepFunction) => void) &
     ((
       pattern: DefineStepPattern,
       options: IDefineStepOptions,
-      code: Function
+      code: TestStepFunction
     ) => void)
-  When: ((pattern: DefineStepPattern, code: Function) => void) &
+  When: ((pattern: DefineStepPattern, code: TestStepFunction) => void) &
     ((
       pattern: DefineStepPattern,
       options: IDefineStepOptions,
-      code: Function
+      code: TestStepFunction
     ) => void)
 }
 

test-d/world.ts

@@ -0,0 +1,33 @@
+import { Before, setWorldConstructor, When, World } from '../'
+
+// should allow us to read parameters and add attachments
+Before(async function () {
+  await this.attach(this.parameters.foo)
+})
+When('stuff happens', async function () {
+  await this.attach(this.parameters.foo)
+})
+
+// should allow us to set and get arbitrary properties
+Before(async function () {
+  this.bar = 'baz'
+  await this.log(this.baz)
+})
+When('stuff happens', async function () {
+  this.bar = 'baz'
+  await this.log(this.baz)
+})
+
+// should allow us to use a custom world class
+class CustomWorld extends World {
+  doThing(): string {
+    return 'foo'
+  }
+}
+setWorldConstructor(CustomWorld)
+Before(async function (this: CustomWorld) {
+  this.doThing()
+})
+When('stuff happens', async function (this: CustomWorld) {
+  this.doThing()
+})