Svelte 5: Better effect_update_depth_exceeded error, show effect location

[KieranP]

Describe the bug

In the process of migration a large app to Svelte 5. Started seeing a ton of effect_update_depth_exceeded errors when running tests (which if I understand correctly means I'm updating state inside of an $effect, which triggers that $effect again, creating a loop?). But there is no information in the error message about which $effect is causing the issue, so I'm having a hard time hunting down the offending effects. Also, these showed up after bumping Svelte package versions, and I don't see anything mentioning this in the upgrades notes, so possible undocumented breaking change.

Reproduction

See above

Logs

No response

System Info

System:
    OS: macOS 15.0.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 259.27 MB / 18.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.15.1 - ~/.asdf/installs/nodejs/20.15.1/bin/node
    Yarn: 4.3.1 - ~/.asdf/installs/nodejs/20.15.1/bin/yarn
    npm: 10.8.2 - ~/.asdf/plugins/nodejs/shims/npm
    bun: 1.1.0 - ~/.bun/bin/bun
  Browsers:
    Chrome: 130.0.6723.70
    Safari: 18.0.1
  npmPackages:
    svelte: ^5.1.0 => 5.1.0

Severity

annoyance

[paoloricciuti]

Hey thanks for reporting, there's already an issue tracking this #13256