feat: Streamline isolation scope handling & reset in isolation scopes

[mydea]

This PR does two things:

1. Removes any usage of propagation context on isolation scope. We never really need/read this, as the current scope one will always overwrite this. Generally we should only ever set/read propagation context on current scope.
2. Adjust server-side withIsolationScope to reset the propagation context unless it is continuing a trace. Today, this kind of works in otel-based places because we wrap root spans in startNewTrace. But this does not align with core/browser handling, so going forward this will be removed. instead, we want this logic to be applied in an isolation scope, so the following code will result in separate traces:

Sentry.withIsolationScope(() => {
  Sentry.startSpan({ name: 'process 1' }, () => ...);
});

Sentry.withIsolationScope(() => {
  Sentry.startSpan({ name: 'process 2' }, () => ...);
});

without this change, both of these spans would be part of the same trace, which is not what we want in server.

note: In browser, we do not actually fork the isolation scope, there is just a single one, so this does not apply.

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	29.82 kB	-0.02%	-3 B 🔽
@sentry/browser - with treeshaking flags	28.02 kB	-0.01%	-2 B 🔽
@sentry/browser (incl. Tracing)	47.07 kB	-0.01%	-4 B 🔽
@sentry/browser (incl. Tracing + Span Streaming)	47.08 kB	-0.02%	-7 B 🔽
@sentry/browser (incl. Tracing, Profiling)	51.81 kB	-0.02%	-10 B 🔽
@sentry/browser (incl. Tracing, Replay)	86.38 kB	-0.02%	-14 B 🔽
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	75.82 kB	-0.02%	-11 B 🔽
@sentry/browser (incl. Tracing, Replay with Canvas)	91.1 kB	-0.02%	-11 B 🔽
@sentry/browser (incl. Tracing, Replay, Feedback)	103.75 kB	-0.01%	-8 B 🔽
@sentry/browser (incl. Feedback)	47.13 kB	-0.01%	-1 B 🔽
@sentry/browser (incl. sendFeedback)	34.66 kB	-0.01%	-3 B 🔽
@sentry/browser (incl. FeedbackAsync)	39.76 kB	-0.01%	-2 B 🔽
@sentry/browser (incl. Metrics)	30.89 kB	-	-
@sentry/browser (incl. Logs)	31.12 kB	-0.01%	-1 B 🔽
@sentry/browser (incl. Metrics & Logs)	31.8 kB	-0.02%	-6 B 🔽
@sentry/react	31.6 kB	-0.04%	-11 B 🔽
@sentry/react (incl. Tracing)	49.31 kB	-0.03%	-13 B 🔽
@sentry/vue	34.74 kB	-0.01%	-2 B 🔽
@sentry/vue (incl. Tracing)	49.04 kB	-0.04%	-15 B 🔽
@sentry/svelte	29.85 kB	-0.01%	-2 B 🔽
CDN Bundle	31.87 kB	-	-
CDN Bundle (incl. Tracing)	47.45 kB	-0.03%	-10 B 🔽
CDN Bundle (incl. Logs, Metrics)	33.42 kB	-0.01%	-3 B 🔽
CDN Bundle (incl. Tracing, Logs, Metrics)	48.82 kB	-0.02%	-7 B 🔽
CDN Bundle (incl. Replay, Logs, Metrics)	72.78 kB	-0.01%	-3 B 🔽
CDN Bundle (incl. Tracing, Replay)	85.06 kB	-0.02%	-14 B 🔽
CDN Bundle (incl. Tracing, Replay, Logs, Metrics)	86.37 kB	-0.02%	-14 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback)	90.84 kB	-0.02%	-14 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)	92.15 kB	-0.02%	-14 B 🔽
CDN Bundle - uncompressed	95.04 kB	-0.08%	-73 B 🔽
CDN Bundle (incl. Tracing) - uncompressed	142.13 kB	-0.15%	-210 B 🔽
CDN Bundle (incl. Logs, Metrics) - uncompressed	99.75 kB	-0.08%	-73 B 🔽
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed	146.11 kB	-0.15%	-210 B 🔽
CDN Bundle (incl. Replay, Logs, Metrics) - uncompressed	224.51 kB	-0.04%	-73 B 🔽
CDN Bundle (incl. Tracing, Replay) - uncompressed	261.39 kB	-0.09%	-210 B 🔽
CDN Bundle (incl. Tracing, Replay, Logs, Metrics) - uncompressed	265.35 kB	-0.08%	-210 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	275.09 kB	-0.08%	-210 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed	279.05 kB	-0.08%	-210 B 🔽
@sentry/nextjs (client)	51.91 kB	-0.02%	-6 B 🔽
@sentry/sveltekit (client)	47.5 kB	-0.03%	-12 B 🔽
@sentry/core/server	79.61 kB	-0.03%	-18 B 🔽
@sentry/core/browser	51.71 kB	+0.01%	+5 B 🔺
@sentry/node	121.41 kB	+0.01%	+4 B 🔺
@sentry/node/import (ESM hook with diagnostics-channel injection)	166 B	-	-
@sentry/node - without tracing	84.98 kB	+0.09%	+70 B 🔺
@sentry/aws-serverless	93.25 kB	+0.07%	+63 B 🔺
@sentry/cloudflare (withSentry) - minified	198.33 kB	-0.02%	-25 B 🔽
@sentry/cloudflare (withSentry)	487.8 kB	+0.02%	+49 B 🔺

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[Lms24]

I think this is a good change!

[Lms24]

it seems like this removes a footgun where we potentially incorrectly merged a propagation context before here. I like it!

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Shared propagation context reference

Low Severity

When restoring the parent trace for non-isolateTrace monitors, setPropagationContext is given the original propagation context object from the parent scope rather than a copy. On strategies that fork the current scope, the monitor scope then aliases the parent's mutable context, so in-place field updates inside the callback can alter the parent.

 

^{Reviewed by Cursor Bugbot for commit 65c8a4c. Configure here.}