fix: trigger full rebuild when a tracked dependency is deleted

[godfengliang]

Fix

Fixes #20113

Problem

When a file in the CLI watcher's tracked full-rebuild dependency set (e.g., a config dependency like my-color.js) is deleted, the watcher does not trigger a rebuild. This happens because all delete events are unconditionally dropped at L485:

if (event.type === 'delete') return

This means deleting my-color.js (which is imported by tailwind.config.js) silently keeps the stale CSS output instead of surfacing the missing dependency error.

Solution

Instead of unconditionally returning on delete events, add the deleted file path to the tracked files set before returning:

if (event.type === 'delete') {
  files.add(event.path)
  return
}

This allows the handle callback (L260-346) to properly detect deleted files that are in fullRebuildPaths and trigger a full rebuild. The full rebuild will then fail with the appropriate "missing module" error, alerting the user.

Test Plan

Follow the reproduction steps from #20113:

1. Create a project with tailwind.config.js importing my-color.js
2. Run tailwindcss --input src/index.css --output dist/out.css --watch
3. Delete my-color.js

Before fix: No rebuild triggered, stale CSS kept.
After fix: Full rebuild triggered, error about missing my-color.js is shown.

[greptile-apps]

Confidence Score: 5/5

Safe to merge — the change is a single-line addition inside the delete-event branch of the watcher, and all existing paths for non-delete events are untouched.

The fix is minimal and surgical: it adds a deleted file's path to the batch set before the early return, then relies entirely on the already-correct handle callback logic to distinguish config deps (full rebuild) from content files (incremental, bails early when no candidates). No new code paths are introduced for the non-delete case, and the debounce/queue flow is unaffected.

No files require special attention.

_{Reviews (2): Last reviewed commit: "fix: correct comment about deleted file ..." | Re-trigger Greptile}

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

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Run ID: 545c4d3f-185b-4cfa-b4c8-2fd9527e9253

📥 Commits

Reviewing files that changed from the base of the PR and between 09daf83 and 1d64663.

📒 Files selected for processing (1)

• packages/@tailwindcss-cli/src/commands/build/index.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/@tailwindcss-cli/src/commands/build/index.ts

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Walkthrough

The PR updates the build command's file watcher so delete events add the deleted path to the tracked files set instead of being ignored. Deleted content files still hit the candidate cache; deleted config/plugin dependencies are now tracked so a later full rebuild can detect and report missing-file errors.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main fix: triggering a full rebuild when a tracked dependency is deleted.
Description check	✅ Passed	The description clearly explains the problem, solution, and test plan, all directly related to the code changes in the PR.
Linked Issues check	✅ Passed	The PR correctly addresses issue #20113 by modifying the delete event handler to add the deleted path to the files set, enabling proper rebuild detection and error reporting for missing dependencies.
Out of Scope Changes check	✅ Passed	All changes are within scope: the modification to the delete event handler in createWatchers directly addresses the core issue of detecting and rebuilding on tracked dependency deletions.

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[RobinMalfait]

Hey! Closing this in favor of #20137 where we also make sure that we can recover if you re-add the same file without requiring the write to the input.css file.

Thanks for the PR!