zed disregards `file_scan_exclusions` at startup and deep-scans directories that were excluded

[eric-seppanen]

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Describe the bug / provide steps to reproduce it

I have been developing a fuse filesystem, and during development testing, I often mount to a path mnt right in my development tree. I added mnt to my file_scan_exclusions setting (and verified it disappears from the left pane as a result).

However, when I (re)start Zed (manually or because of an update), I can see in my fuse filesystem logs that Zed is deep-scanning the entire tree inside my fuse filesystem. Because this is a virtual filesystem that is arbitrarily large, this manifests as a blank editor window with an empty left pane and little functionality (e.g. I can't browse my project's files).

If I close the malfunctioning Zed window, the filesystem scanning continues: there is a zed-editor process in the background that keeps running until I unmount the fuse filesystem.

I can see (from my fuse filesystem logs) that it is traversing every directory and repeatedly trying to access .git and .gitignore in every possible path.

If I start the fuse filesystem after Zed is running, everything works normally.

I'm not sure how to share steps to reproduce this because running a fuse filesystem in the development tree is a bit exotic. My guess is that even without fuse, something like strace would be able to confirm that Zed is ignoring file_scan_exclusions and scanning excluded paths during some phase of startup? I'm open to ideas for gathering data that would help.

Environment

Zed: v0.162.5 (Zed)
OS: Linux Wayland ubuntu 24.04
Memory: 31.1 GiB
Architecture: x86_64
GPU: Intel(R) Graphics (RPL-P) || Intel open-source Mesa driver || Mesa 24.0.9-0ubuntu0.2

If applicable, add mockups / screenshots to help explain present your vision of the feature

If applicable, attach your Zed.log file to this issue.

Unfortunately, when this scan/hang occurs nothing is printed to Zed.log.

[notpeter]

I am able to reproduce:

cd /tmp
git clone git@github.com:zed-industries/extensions.git
cd extensions
git submodule init
git submodule update
mkdir -p .zed/
echo '{ "file_scan_exclusions": ["extensions"] }' > .zed/settings.json
zed .

Observed behavior: Zed takes many seconds to load (scanning the excluded extensions/), then it will briefly show the project panel tree with the extensions folder before hiding it.

Expected behavior: zed loads quickly by skipping the 15GB under extensions/.

Note: this becomes less reproducible if you try and repeat this (I assume because the 15GB of submodules stick around in the file cache). But you should be able to reliably reproduce if you clone into a new directory.

Thank you for reporting.

[mgsloan]

The repro doesn't trigger a bug for me. Maybe it got fixed by some other change to this code? If I run with RUST_LOG=debug I see this in the logs:

[2025-02-17T15:46:28-07:00 DEBUG worktree] skipping excluded child entry "extensions"

[eric-seppanen]

I just re-tested this on Zed 0.173.11 and it's still broken for me.

I would re-open this issue but I don't have permissions?

[eric-seppanen]

@mgsloan The file_scan_exclusions setting always hid the directories from some parts of the editor: for example, it's hidden from the left pane. Perhaps the log message is from that part?

I also tried RUST_LOG=debug zed . with no other editor windows running, but I didn't get debug logs.