Ignore window.fetch network error (#38)

Co-authored-by: Sindre Sorhus <[email protected]>

Author: oreporan

index.d.ts

@@ -52,7 +52,8 @@ declare const pRetry: {
 	/**
 	Returns a `Promise` that is fulfilled when calling `input` returns a fulfilled promise. If calling `input` returns a rejected promise, `input` is called again until the max retries are reached, it then rejects with the last rejection reason.
 
-	It doesn't retry on `TypeError` as that's a user error.
+	It doesn't retry on `TypeError` as that's a user error. The only exclusion to this logic is when `TypeError` is thrown by `fetch`'s API with the message 'Failed to fetch', [which indicates that a request was not successful due to a network error](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Checking_that_the_fetch_was_successful). 
+	However, beware that `fetch` may throw `TypeError` with different error messages on different platforms for similar situations. See [whatwg/fetch#526 (comment)](https://github.com/whatwg/fetch/issues/526#issuecomment-554604080)."  
 
 	@param input - Receives the number of attempts as the first argument and is expected to return a `Promise` or any value.
 	@param options - Options are passed to the [`retry`](https://github.com/tim-kos/node-retry#retryoperationoptions) module.

index.js

@@ -48,7 +48,7 @@ const pRetry = (input, options) => new Promise((resolve, reject) => {
 			if (error instanceof AbortError) {
 				operation.stop();
 				reject(error.originalError);
-			} else if (error instanceof TypeError) {
+			} else if (error instanceof TypeError && error.message !== 'Failed to fetch') {
 				operation.stop();
 				reject(error);
 			} else {

readme.md

@@ -38,7 +38,8 @@ const run = async () => {
 
 Returns a `Promise` that is fulfilled when calling `input` returns a fulfilled promise. If calling `input` returns a rejected promise, `input` is called again until the maximum number of retries is reached. It then rejects with the last rejection reason.
 
-It doesn't retry on `TypeError` as that's a user error.
+
+It doesn't retry on `TypeError` as that's a user error. The only exclusion to this logic is when `TypeError` is thrown by `fetch`'s API with the message 'Failed to fetch', [which indicates that a request was not successful due to a network error](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Checking_that_the_fetch_was_successful). However, beware that `fetch` may throw `TypeError` with different error messages on different platforms for similar situations. See [whatwg/fetch#526 (comment)](https://github.com/whatwg/fetch/issues/526#issuecomment-554604080)."  
 
 #### input
 

test.js

@@ -48,6 +48,20 @@ test('no retry on TypeError', async t => {
 	t.is(i, 1);
 });
 
+test('retry on TypeError - failed to fetch', async t => {
+	const typeErrorFixture = new TypeError('Failed to fetch');
+	let index = 0;
+
+	const returnValue = await pRetry(async attemptNumber => {
+		await delay(40);
+		index++;
+		return attemptNumber === 3 ? fixture : Promise.reject(typeErrorFixture);
+	});
+
+	t.is(returnValue, fixture);
+	t.is(index, 3);
+});
+
 test('AbortError - string', t => {
 	const error = new pRetry.AbortError('fixture').originalError;
 	t.is(error.constructor.name, 'Error');