TypeScript def file and build time detection

README.md

@@ -35,6 +35,9 @@ Available imports:
 import fetch, { Headers, Request, Response, AbortController } from 'fetch';
 ```
 
+### Use with TypeScript
+To use `ember-fetch` with TypeScript or enable editor's type support, add `"fetch": "ember-cli/ember-fetch"` to your app's `devDependencies`.
+
 ### Use with Ember Data
 To have Ember Data utilize `fetch` instead of jQuery.ajax to make calls to your backend, extend your project's `application` adapter with the `adapter-fetch` mixin.
 
@@ -65,7 +68,7 @@ export default {
 }
 ```
 
-For addon authors, if the addon supports Fastboot mode, `ember-fetch` should also be listed as a [peer dependency](https://docs.npmjs.com/files/package.json#peerdependencies). 
+For addon authors, if the addon supports Fastboot mode, `ember-fetch` should also be listed as a [peer dependency](https://docs.npmjs.com/files/package.json#peerdependencies).
 This is because Fastboot only invokes top-level addon's `updateFastBootManifest` ([detail](https://github.com/ember-fastboot/ember-cli-fastboot/issues/597)), thus `ember-fetch` has to be a top-level addon installed by the host app.
 
 ### Allow native fetch

index.d.ts

@@ -1,9 +1,26 @@
-// Type definitions for Ember Fetch
+// Type definitions for ember-fetch
 // Project: https://github.com/ember-cli/ember-fetch
-// Definitions by: Toran Billups <https://github.com/toranb>
-// TypeScript Version: 2.3
+// Definitions by: Toran Billups <https://github.com/toranb>, Thomas Wang<https://github.com/xg-wang>
+/// <reference lib="es2015" />
+/// <reference lib="dom" />
 
-declare module 'fetch' {
-  import RSVP from 'rsvp';
-  export default function fetch(input: RequestInfo, init?: RequestInit): RSVP.Promise<Response>;
-}
+import RSVP from 'rsvp';
+export default function fetch(input: RequestInfo, init?: RequestInit): RSVP.Promise<Response>;
+export const Headers: {
+  prototype: Headers;
+  new(init?: HeadersInit): Headers;
+};
+export const Request: {
+  prototype: Request;
+  new(input: RequestInfo, init?: RequestInit): Request;
+};
+export const Response: {
+  prototype: Response;
+  new(body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
+  redirect(url: string, status?: number): Response;
+};
+export const AbortController: {
+  prototype: AbortController;
+  new(): AbortController;
+};

index.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const path = require('path');
+const fs = require('fs');
 // We use a few different Broccoli plugins to build our trees:
 //
 // broccoli-templater: renders the contents of a file inside a template.
@@ -97,6 +98,14 @@ module.exports = {
         ]
       }
     });
+
+    // Detect `tsconfig.json` as the evidence user need type support
+    if (
+      fs.existsSync(path.join(app.project.root, 'tsconfig.json')) &&
+      !('fetch' in app.project.pkg.devDependencies)
+    ) {
+      app.project.ui.writeWarnLine('To use ember-fetch with TypeScript, please add devDependency "fetch": "ember-cli/ember-fetch"');
+    }
   },
 
   /*

tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "compilerOptions": {
+    "noEmit": true,
+    "lib": [],
+    "types": []
+  },
+  "files": ["index.d.ts"]
+}