Use extension handle to identify extensions in file-watcher

[isaacroldan]

WHY are these changes introduced?

The file watcher was using extension directory paths to identify which extensions are affected by file changes. This approach has limitations when dealing with shared files or when extensions need to be uniquely identified beyond their filesystem location.

WHAT is this pull request doing?

Refactors the file watcher system to use extension handles instead of directory paths for tracking file ownership and identifying affected extensions. The changes include:

• Added extensionHandle field to WatcherEvent interface to uniquely identify extensions
• Modified file tracking to map file paths to extension handles rather than directory paths
• Updated event filtering logic to use extension handles when available, falling back to directory paths for folder-level events
• Enhanced test cases to verify the new event structure and handle multiple events correctly
• Improved event deduplication to consider extension handles alongside path and type

The extensionPath field is retained for backward compatibility and folder-level events where no extension handle exists yet.

How to test your changes?

1. Run the existing file watcher tests to ensure all functionality works as expected
2. Test file changes in extensions to verify events are properly attributed to the correct extension handles
3. Test extension creation/deletion scenarios to ensure folder-level events still work correctly
4. Verify that shared files between extensions generate separate events for each affected extension

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing, so I've added a changelog entry with pnpm changeset add

[isaacroldan]

• Extract custom watch paths to specifications #7220 : 2 dependent PRs (#7226 , #7227 )
• Use extension handle to identify extensions in file-watcher #7224 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[Copilot]

Pull request overview

This PR refactors the dev file-watcher event model to attribute file changes to extensions by extension handle rather than only by extension directory path, enabling correct handling of shared files across multiple extensions.

Changes:

• Adds extensionHandle?: string to WatcherEvent and threads it through event creation/deduping.
• Changes watched-file ownership tracking to map file paths → extension handles.
• Updates watcher event handling logic (and tests) to support multiple events for shared files.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/app/src/cli/services/dev/app-events/file-watcher.ts	Emits watcher events with extensionHandle and tracks watched files by handle.
packages/app/src/cli/services/dev/app-events/file-watcher.test.ts	Adjusts tests to allow multiple emitted events for a single FS change.
packages/app/src/cli/services/dev/app-events/app-event-watcher-handler.ts	Resolves affected extensions by extensionHandle when present, otherwise by directory.

Comments suppressed due to low confidence (1)

packages/app/src/cli/services/dev/app-events/file-watcher.test.ts:383

• When expectedEventCount is 2, the test still only asserts against actualEvents[0]. Since the watcher can emit multiple events in either order (and the whole point of this PR is to differentiate them via extensionHandle), this can become order-dependent/flaky and it also doesn't validate that extensionHandle is set correctly. Prefer asserting that actualEvents contains an event matching expectedEvent (and, when multiple events are expected, assert the full set of extensionHandle values or the full list of expected events) rather than assuming index 0.

            const calls = onChange.mock.calls
            const actualEvents = calls.find((call) => call[0].length > 0)?.[0]

            if (!actualEvents) {
              throw new Error('Expected onChange to be called with events, but all calls had empty arrays')
            }

            const eventCount = expectedEventCount ?? 1
            expect(actualEvents).toHaveLength(eventCount)
            const actualEvent = actualEvents[0]

            expect(actualEvent.type).toBe(expectedEvent.type)
            expect(actualEvent.path).toBe(normalizePath(expectedEvent.path))
            expect(actualEvent.extensionPath).toBe(normalizePath(expectedEvent.extensionPath))
            expect(Array.isArray(actualEvent.startTime)).toBe(true)

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.