fix(browser): Improve handling of 0 and undefined resource timing values

[Lms24]

Our previous resource timing implementation had two flaws:

• we'd convert undefined resoure timing values to 0, leading to them being converted the absolute timeOrigin timestamp
  • this would happen if we read performance entries from browsers that don't support the respective timing information
• we'd convert 0 resource timing values to the absolue timeOrigin timestamp
  • this happens frequently for requests made to cross-origin sources that don't respond with a matching Timing-Allow-Origin header, since a lot of the detailed timing information is guarded by browsers.

This PR

• drops any timing attributes where the original value was undefined
• sends 0 for any timing values that were originally 0 (i.e. no longer converts them to the timeOrigin absolute timestamp)

closes https://linear.app/getsentry/issue/JS-968/investigate-httprequestfetch-start-after-httprequestresponse-start

[linear]

JS-968 Investigate http.request.fetch_start after http.request.response_start

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	24.26 kB	-	-
@sentry/browser - with treeshaking flags	22.77 kB	-	-
@sentry/browser (incl. Tracing)	40.43 kB	+0.08%	+32 B 🔺
@sentry/browser (incl. Tracing, Replay)	78.81 kB	+0.05%	+32 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	68.48 kB	+0.05%	+33 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	83.48 kB	+0.05%	+36 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	95.69 kB	+0.04%	+29 B 🔺
@sentry/browser (incl. Feedback)	40.97 kB	-	-
@sentry/browser (incl. sendFeedback)	28.91 kB	-	-
@sentry/browser (incl. FeedbackAsync)	33.84 kB	-	-
@sentry/react	25.98 kB	-	-
@sentry/react (incl. Tracing)	42.41 kB	+0.09%	+34 B 🔺
@sentry/vue	28.78 kB	-	-
@sentry/vue (incl. Tracing)	42.24 kB	+0.08%	+33 B 🔺
@sentry/svelte	24.29 kB	-	-
CDN Bundle	25.77 kB	-	-
CDN Bundle (incl. Tracing)	40.33 kB	+0.08%	+31 B 🔺
CDN Bundle (incl. Tracing, Replay)	76.56 kB	+0.05%	+36 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	82.05 kB	+0.05%	+35 B 🔺
CDN Bundle - uncompressed	75.37 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	119.39 kB	+0.09%	+99 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	234.51 kB	+0.05%	+99 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	247.27 kB	+0.05%	+99 B 🔺
@sentry/nextjs (client)	44.42 kB	+0.07%	+27 B 🔺
@sentry/sveltekit (client)	40.85 kB	+0.09%	+33 B 🔺
@sentry/node-core	50.02 kB	-0.01%	-1 B 🔽
@sentry/node	152.83 kB	-	-
@sentry/node - without tracing	91.94 kB	-0.01%	-1 B 🔽
@sentry/aws-serverless	105.39 kB	-	-

View base workflow run

[Lms24]

this is probably useful to be extracted into browser or core at some point. I know we had our reservations against dropUndefinedKeys but IIRC this was mainly due to over-usage and it recursively going through the object. I think a light-weight implementation like this one should be fine but happy to hear other opinions.

Main motivation for using it in browser: it's more size-efficient than checking every value for definedness before adding the attribute.

[mydea]

nice, this makes sense to me! We should make sure we handle this appropriately in product, as this could also be confusing to users why this would be 0/

[AbhiPrasad]

good change!