Fix throws (#310)

* revert to throws behaviour from v5 of library

* docs

docs/api.md

@@ -33,7 +33,7 @@ Replaces `fetch` with a stub which records its calls, grouped by route, and opti
         * `body`: Set the response body (`string` or `object`)
         * `status`: Set the response status (default `200`)
         * `headers`: Set the response headers. (`object`)
-        * `throws`: If this property is present then a the value of `throws` is thrown
+        * `throws`: If this property is present then fetch returns a `Promise` rejected with the value of `throws`
         * `sendAsJson`: This property determines whether or not the request body should be converted to `JSON` before being sent (defaults to `true`).
         * `includeContentLength`: Set this property to true to automatically add the `content-length` header (defaults to `true`).
         * `redirectUrl`: *experimental* the url the response should be from (to imitate followed redirects - will set `redirected: true` on the response)

src/lib/fetch-handler.js

@@ -6,14 +6,6 @@ FetchMock.fetchHandler = function (url, opts) {
 
 	let response = this.executeRouter(url, opts);
 
-	// If the response says to throw an error, throw it
-	// It only makes sense to do this before doing any async stuff below
-	// as the async stuff swallows catastrophic errors in a promise
-	// Type checking is to deal with sinon spies having a throws property :-0
-	if (response.throws && typeof response !== 'function') {
-		throw response.throws;
-	}
-
 	// this is used to power the .flush() method
 	let done
 	this._holdingPromises.push(new this.config.Promise(res => done = res));
@@ -55,6 +47,7 @@ FetchMock.executeRouter = function (url, opts) {
 }
 
 FetchMock.generateResponse = async function (response, url, opts) {
+
 	// We want to allow things like
 	// - function returning a Promise for a response
 	// - delaying (using a timeout Promise) a function's execution to generate
@@ -71,6 +64,12 @@ FetchMock.generateResponse = async function (response, url, opts) {
 		}
 	}
 
+	// If the response says to throw an error, throw it
+	// Type checking is to deal with sinon spies having a throws property :-0
+	if (response.throws && typeof response !== 'function') {
+		throw response.throws;
+	}
+
 	// If the response is a pre-made Response, respond with it
 	if (this.config.Response.prototype.isPrototypeOf(response)) {
 		return response;

test/specs/responses.test.js

@@ -84,11 +84,6 @@ e.g. {"body": {"status: "registered"}}`)
 					expect(res.headers.get('content-type')).not.to.exist;
 				});
 
-				it('throw `throws` property exists', async () => {
-					fm.mock('http://it.at.there/', {throws: 'exists'});
-					expect(() => fm.fetchHandler('http://it.at.there/')).to.throw();
-				});
-
 				it('not convert if `status` property exists', async () => {
 					fm.mock('http://it.at.there/', {status: 300});
 					const res = await fm.fetchHandler('http://it.at.there/')
@@ -204,6 +199,7 @@ e.g. {"body": {"status: "registered"}}`)
 		});
 
 		describe('response negotiation', () => {
+
 			it('function', async () => {
 				fm.mock('http://it.at.there/', url => url);
 				const res = await fm.fetchHandler('http://it.at.there/');
@@ -231,19 +227,6 @@ e.g. {"body": {"status: "registered"}}`)
 				expect(await res.text()).to.equal('http://it.at.there/');
 			});
 
-			it('response that throws', async () => {
-				fm.mock('http://it.at.there/', {
-					throws: 'Oh no'
-				});
-
-				try {
-					fm.fetchHandler('http://it.at.there/')
-					expect(true).to.be.false
-				} catch (err) {
-					expect(err).to.equal('Oh no');
-				}
-			});
-
 			it('Response', async () => {
 				fm.mock('http://it.at.there/', new fm.config.Response('http://it.at.there/', {status: 200}));
 				const res = await fm.fetchHandler('http://it.at.there/');
@@ -262,6 +245,32 @@ e.g. {"body": {"status: "registered"}}`)
 				expect(res.status).to.equal(200);
 			});
 
+			describe('rejecting', () => {
+				it('reject if object with `throws` property', async () => {
+					fm.mock('http://it.at.there/', {throws: 'as expected'});
+
+					return fm.fetchHandler('http://it.at.there/')
+						.then(() => {
+							throw 'not as expected';
+						})
+						.catch(err => {
+							expect(err).to.equal('as expected');
+						})
+				});
+
+				it('reject if function that returns object with `throws` property', async () => {
+					fm.mock('http://it.at.there/', () => ({throws: 'as expected'}));
+
+					return fm.fetchHandler('http://it.at.there/')
+						.then(() => {
+							throw 'not as expected';
+						})
+						.catch(err => {
+							expect(err).to.equal('as expected');
+						})
+				});
+
+			})
 		});
 
 	});