fix: improve handling of file and directory events in FlowsMapper

[reubenmiller]

Proposed changes

Fixes flow being permanently lost from memory after a package manager updates it (deletes then recreates the files), even though files are restored on disk (#4023).

Three targeted fixes:

1. remove_script() — unload instead of remove (registry.rs)

When a script file is deleted, flows referencing it are now unloaded (moved to unloaded_flows) instead of being silently ignored with a warning. This means when the script is restored and reload_script() calls drain_unloaded(), the flow is rediscovered and reloaded automatically.

Previously, remove_script() only logged a warning and returned early — the flow stayed in the flows map with a broken script reference but was never re-evaluated when the script came back.

2. add_flow() — no-op on missing file instead of destructive removal (registry.rs)

Changed from if tokio::fs::read_to_string().is_err() → remove_flow() to if !path.is_file() → return.

The old code would destroy a valid in-memory flow on a transient read failure (e.g. file briefly absent during a package update). The new code simply returns — if the file was truly deleted, a FileDeleted event will handle removal; if it's being replaced, a subsequent Modified event will reload it.

3. on_file_removed() — skip stale FileDeleted events (actor.rs)

Added a path.exists() guard at the top of on_file_removed(). During a package update, FileDeleted events can arrive after the file has already been re-created. Without this guard, the stale event would remove the freshly-reloaded flow.

Also added the missing send_updated_subscriptions() + update_flow_status() calls for script removals, which were previously only done for .toml removals.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

#4023

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s. You can activate automatic signing by running just prepare-dev once)
• I ran just format as mentioned in CODING_GUIDELINES
• I used just check as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
858	0	3	858	100	2h41m12.544329s

[codecov]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/extensions/tedge_flows/src/registry.rs	0.00%	11 Missing ⚠️
crates/extensions/tedge_flows/src/actor.rs	0.00%	5 Missing ⚠️

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[Bravo555]

FileDeleted(flow.toml) (stale, delayed past the debounce window) → ❌ "Removing flow" — flow removed again from a stale event

I'm not able to observe this when running the Flow is reloaded after package-style replacement test.

I placed the breakpoint at Install Lifecycle Flow main-v1.js line and after running "Debug test" ran the following commands to enable debug log from tedge_flows:

$ systemctl edit tedge-mapper-local

# place these lines in the region indicated by `systemctl edit`
[Service]
Environment=RUST_LOG=debug

$ systemctl restart tedge-mapper-local
$ journalctl -f -u tedge-mapper-local

Then I continued until Simulate package install: step and ran that. These are the messages sent by inotify:

2026-03-11T15:32:21.891735368Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send Modified("/etc/tedge/mappers/local/flows/lifecycle-test/flow.toml")
2026-03-11T15:32:21.891756037Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send FileDeleted("/etc/tedge/mappers/local/flows/lifecycle-test/flow.toml")
2026-03-11T15:32:21.891760576Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send Modified("/etc/tedge/mappers/local/flows/lifecycle-test/main.js")
2026-03-11T15:32:21.891763902Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send FileDeleted("/etc/tedge/mappers/local/flows/lifecycle-test/main.js")
2026-03-11T15:32:21.891767569Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send FileCreated("/etc/tedge/mappers/local/flows/lifecycle-test/flow.toml")
2026-03-11T15:32:21.891770926Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send Modified("/etc/tedge/mappers/local/flows/lifecycle-test/flow.toml")
2026-03-11T15:32:21.891774372Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send FileCreated("/etc/tedge/mappers/local/flows/lifecycle-test/main.js")
2026-03-11T15:32:21.891777929Z DEBUG Inotify: /workspace/crates/core/tedge_actors/src/message_boxes.rs:212: send Modified("/etc/tedge/mappers/local/flows/lifecycle-test/main.js")

There are FileDeleted events, but there are also FileCreated and Modified events after that, which should cause the flow to be properly reloaded.

[Bravo555]

Fixes the problem with reloading scripts, approved

[didier-wenzek]

Approved

[didier-wenzek]

if matches!(path.extension(), Some("js" | "ts" | "mjs")) {
    self.processor.remove_script(path).await;
} else if path.extension() == Some("toml") {
    self.processor.remove_flow(path).await;
}
self.send_updated_subscriptions().await?;
self.update_flow_status(path).await?;

[reubenmiller]

I guess that assumes that we don't get any other notifications which are from .js, .ts, .mjs nor .toml files?

[didier-wenzek]

You are correct, we have to handle the case of a flows unrelated file.

[reubenmiller]

I pushed the recommended change