fix(editor): never let the editor save over a style it never loaded

[ankit]

Opening Stylebot on a site could delete that site's style outright, and with sync on the deletion fanned out to Drive and other devices.

Root cause

The editor cannot tell "your style failed to load" from "this page has no style".

getAll() is items['styles'] || {}, so a storage read that comes back empty still lets GetStylesForPage answer successfully with { styles: [], defaultStyle: undefined }. The content script then:

• keeps url = document.domain — which is exactly how site-wide styles are keyed
• keeps css = ''
• resolves ready, so the editor opens completely normally

Any save from that state writes empty css, and set() treats empty css as "delete this style". Opening the editor was enough to lose it. The pop-out window made it likelier, because the window is a second writer that saves on mount.

Reproduced via an equivalent route — a tab loaded before the style existed, since SetStyle never pushes to other tabs: style present, open the editor, a zero-length write lands, entry gone.

Fix

One guard, at the chokepoint every editor write passes through:

// applyCss
if (!css && !state.css) {
  return;
}

Holding no css, there is nothing to clear. Verified this alone stops the reproduction, so it covers any route in — including a failed read.

Deleting a style still works: that is always a non-empty → empty transition, so state.css is set and the guard doesn't fire. Confirmed end to end (storage ["localhost"] → [], css removed from the page), and the existing grayscale-reset and code-typing e2e tests exercise real deletes.

Also: the code editor now prunes empty rules only when that changes something, so opening it no longer re-saves identical css — which was restamping modifiedTime and scheduling a sync on every open.

Tests

Unit tests — this is store behaviour and doesn't need a browser. Both were verified to fail against the pre-fix code, not merely to pass:

• applyCss refuses an empty save when nothing was loaded
• applyCss still clears a style the editor was showing

667 unit tests, e2e 44/44, lint and typecheck clean.

Deliberately not included

• Refreshing the stored style on open. An earlier revision re-read storage as the editor opened, so the panel never showed a stale or blank copy. Dropped: it isn't what prevents the deletion, and it made every open wait on a background round trip. The blank-panel symptom and the cross-tab lost update are separate bugs.
• getAll() masking read failures. Every caller still can't distinguish a failed read from an empty profile. The editor can no longer destroy data because of it, but the underlying ambiguity remains.

🤖 Generated with Claude Code