wrap JSON.parse's SynaxError with FetchError

src/body.js

@@ -87,7 +87,14 @@ Body.prototype = {
 	 * @return  Promise
 	 */
 	json() {
-		return consumeBody.call(this).then(buffer => JSON.parse(buffer.toString()));
+		return consumeBody.call(this).then((buffer) => {
+			return JSON.parse(buffer.toString());
+		}).catch((err) => {
+			if (err instanceof SyntaxError) {
+				return Body.Promise.reject(new FetchError(`invalid json response body at ${this.url} reason: ${err.message}`, 'invalid-json'));
+			}
+			throw err;
+		})
 	},
 
 	/**

test/test.js

@@ -446,7 +446,9 @@ describe('node-fetch', () => {
 		url = `${base}error/json`;
 		return fetch(url).then(res => {
 			expect(res.headers.get('content-type')).to.equal('application/json');
-			return expect(res.json()).to.eventually.be.rejectedWith(Error);
+			return expect(res.json()).to.eventually.be.rejected
+				.and.be.an.instanceOf(FetchError)
+				.and.include({ type: 'invalid-json' });
 		});
 	});
 
@@ -463,6 +465,18 @@ describe('node-fetch', () => {
 		});
 	});
 
+	it('should reject when trying to parse no content response as json', function() {
+		url = `${base}no-content`;
+		return fetch(url).then(res => {
+			expect(res.status).to.equal(204);
+			expect(res.statusText).to.equal('No Content');
+			expect(res.ok).to.be.true;
+			return expect(res.json()).to.eventually.be.rejected
+				.and.be.an.instanceOf(FetchError)
+				.and.include({ type: 'invalid-json' });
+		});
+	});
+
 	it('should handle no content response with gzip encoding', function() {
 		url = `${base}no-content/gzip`;
 		return fetch(url).then(res => {