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fix: fetch errors do not have responses #2564

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Merged
merged 3 commits into from
May 27, 2020
Merged

fix: fetch errors do not have responses #2564

merged 3 commits into from
May 27, 2020

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rossipedia
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Originally I was going to file an issue, but I figured it'd be more useful to just PR the fix

Package + Version

  • @sentry/browser

Version:

5.15.5

Description

fetch breadcrumbs attempts to access a non-existent response object.

fetch treats all responses as a success, regardless of the HTTP status code. When fetch throws an error, it won't have a response.

Details

To reproduce the error, you can use this small HTML file:

<!DOCTYPE html>
<script src="https://browser.sentry-cdn.com/5.15.5/bundle.min.js"></script>
<script>
Sentry.init({
    dsn: "YOUR_PUBLIC_DSN",
    debug: true,
});
fetch("https://some-domain-that.doesnt-exist.com");
</script>

Explanation

The handlers for fetch do not add a response object when an error occurs (correctly, as one does not exist in this case):

sentry-javascript/packages/utils/src/instrument.ts

Lines 166 to 173 in 03d9ef0

(error: Error) => {
triggerHandlers('fetch', {
...commonHandlerData,
endTimestamp: Date.now(),
error,
});
throw error;
},

However, in the code for adding the fetch breadcrumbs, there is an unconditional attempt to access the response.status property in the error case:

sentry-javascript/packages/browser/src/integrations/breadcrumbs.ts

Lines 188 to 196 in 03d9ef0

if (handlerData.error) {
getCurrentHub().addBreadcrumb(
{
category: 'fetch',
data: {
...handlerData.fetchData,
status_code: handlerData.response.status,
},
level: Severity.Error,

Which leads to the error shown:

image

@rossipedia rossipedia requested a review from kamilogorek as a code owner April 29, 2020 21:25
HazAT
HazAT approved these changes May 27, 2020
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@HazAT HazAT left a comment

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Thank you! Solid change and good description!
Sorry for the delay.

@HazAT HazAT merged commit 031b020 into getsentry:master May 27, 2020
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@HazAT HazAT HazAT approved these changes

@kamilogorek kamilogorek Awaiting requested review from kamilogorek

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2 participants
@rossipedia @HazAT