core: Warn when using data

src/body.js

@@ -177,7 +177,10 @@ Object.defineProperties(Body.prototype, {
 	arrayBuffer: {enumerable: true},
 	blob: {enumerable: true},
 	json: {enumerable: true},
-	text: {enumerable: true}
+	text: {enumerable: true},
+	data: {get: deprecate(() => {},
+		'data doesn\'t exist, use json(), text(), arrayBuffer(), or body instead',
+		'https://github.com/node-fetch/node-fetch/issues/1000 (response)')}
 });
 
 /**

src/request.js

@@ -7,6 +7,7 @@
  */
 
 import {format as formatUrl} from 'node:url';
+import {deprecate} from 'node:util';
 import Headers from './headers.js';
 import Body, {clone, extractContentType, getTotalBytes} from './body.js';
 import {isAbortSignal} from './utils/is.js';
@@ -30,6 +31,10 @@ const isRequest = object => {
 	);
 };
 
+const doBadDataWarn = deprecate(() => {},
+	'.data is not a valid RequestInit property, use .body instead',
+	'https://github.com/node-fetch/node-fetch/issues/1000 (request)');
+
 /**
  * Request class
  *
@@ -58,6 +63,10 @@ export default class Request extends Body {
 		let method = init.method || input.method || 'GET';
 		method = method.toUpperCase();
 
+		if ('data' in init) {
+			doBadDataWarn();
+		}
+
 		// eslint-disable-next-line no-eq-null, eqeqeq
 		if ((init.body != null || (isRequest(input) && input.body !== null)) &&
 			(method === 'GET' || method === 'HEAD')) {

test/referrer.js

@@ -127,7 +127,7 @@ describe('Request constructor', () => {
 			expect(() => {
 				const req = new Request('http://example.com', {referrer: 'foobar'});
 				expect.fail(req);
-			}).to.throw(TypeError, 'Invalid URL: foobar');
+			}).to.throw(TypeError, /Invalid URL/);
 		});
 	});
 

test/request.js

@@ -283,4 +283,16 @@ describe('Request', () => {
 			expect(result).to.equal('a=1');
 		});
 	});
+
+	it('should warn once when using .data (request)', () => new Promise(resolve => {
+		process.once('warning', evt => {
+			expect(evt.message).to.equal('.data is not a valid RequestInit property, use .body instead');
+			resolve();
+		});
+
+		// eslint-disable-next-line no-new
+		new Request(base, {
+			data: ''
+		});
+	}));
 });

test/response.js

@@ -248,4 +248,13 @@ describe('Response', () => {
 		expect(res.status).to.equal(0);
 		expect(res.statusText).to.equal('');
 	});
+
+	it('should warn once when using .data (response)', () => new Promise(resolve => {
+		process.once('warning', evt => {
+			expect(evt.message).to.equal('data doesn\'t exist, use json(), text(), arrayBuffer(), or body instead');
+			resolve();
+		});
+
+		new Response('a').data;
+	}));
 });