The #248 store-side empty-guard (onStoreDocument) unconditionally refuses to
overwrite non-empty persisted content with an empty document, because a
momentarily-empty live Y.Doc is indistinguishable from a real clear at the
store layer. That correctly blocks glitches/bad-merges, but also blocks a user
who genuinely wants to empty a page. This re-introduces a WORKING, narrow,
non-spoofable exception (the dead context.intentionalClear hatch #248 removed
never had a real channel).
Definition of an intentional clear (client, IntentionalClear editor extension):
a LOCAL user transaction (docChanged, NOT a remote y-sync change — filtered via
isChangeOrigin) that reduces a non-empty doc to the empty single-paragraph
shape. This is exactly the select-all + Delete/Backspace keystroke path.
Transport (option b — hocuspocus stateless message): on that transition the
client sends a `{type:'intentional-clear'}` stateless message. The server
(PersistenceExtension.onStateless) records a short-lived (TTL 60s > 45s
maxDebounce), single-use "pending clear" flag keyed by the connection's
document. The next debounced onStoreDocument consumes it on the empty-guard
branch to let that one empty write through.
Why this is the right channel and non-spoofable:
- Yjs transaction origin/metadata does not survive to the server store; awareness
is per-connection and racy. A stateless message ties the signal to a specific
clear, survives the debounce, and rides the authenticated connection.
- The document is taken from the connection, never the payload, so a client
cannot target another page.
- The flag is read ONLY on the empty-over-non-empty branch, so the worst a forged
signal can do is clear a page the connection may already edit; it can never
force or alter a non-empty write. Read-only connections cannot arm it. Every
non-empty store drops a pending flag, so "cleared then retyped" leaves nothing
usable; the flag is single-use and TTL-bounded.
NOTE: #248 is not yet on develop, so the empty-guard block is included here as
the foundation this exception extends. If #248 lands first this rebases cleanly
(the guard logic is identical; the #251-unique additions are the exception,
onStateless, the pending-flag state, and the client extension).
Tests:
- Server (real transport path, not a hand-poke): onStateless sets the flag with
the exact client payload, then the debounced onStoreDocument persists the empty
doc; plus single-use consumption, read-only rejection, non-empty-store drops
the flag, and the unchanged #248 guard tests (empty-over-non-empty blocked,
empty-over-empty allowed).
- Client: a real Editor + the actual selectAll+deleteSelection command emits the
signal; typing / non-emptying edits / already-empty docs do not.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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