rust-url's debugger_visualizer tests are broken in rustc nightly-2024-08-13

[valenting]

I was looking into servo/rust-url#967 but I wasn't able to reproduce the failures locally. Then I realized I was running an older nightly.

I used bisect-rustc and got the following output:

---

searched nightlies: from nightly-2024-08-01 to nightly-2024-09-16
regressed nightly: nightly-2024-08-13
searched commit range: 41dd149...91376f4
regressed commit: 13f8a57

bisected with cargo-bisect-rustc v0.6.9

Host triple: x86_64-pc-windows-msvc
Reproduce with:

cargo bisect-rustc --start=2024-08-01 --end=2024-09-16 --test-dir=rust-url -- test --test debugger_visualizer --features url/debugger_visualizer,url_debug_tests/debugger_visualizer -- --test-threads=1 --nocapture

---

The PR that introduced the issue seems to be: #126793

Example failing job: https://github.com/servo/rust-url/actions/runs/10879435038/job/30184131451

[jieyouxu]

cc @saethlin since you authored #126793 and are more familiar with debuggers

[saethlin]

The issue is that you need to update your natvis file for the new level of nesting in Vec, probably this line:
https://github.com/servo/rust-url/blob/22b823708a59a50ea2505c3fcdb5c4b26ab9b080/debug_metadata/url.natvis#L4

You could use the changes to our own natvis file in that PR you bisected to as a guide.

I've removed the regression and bug labels, because (unfortunately) doing cool debugger stuff like this means you are depending on unstable library internals. If only we could teach debuggers how to go through our stable APIs to get the information 🙃

[valenting]

@saethlin thank you for the suggestion. Very much appreciated!
Feel free to close this bug.

[jieyouxu]

Closing as unfortunately not super actionable in terms of rustc/std.