neuwirth
/
pmacs
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

docs(lane): the identity-undo lane is taken, and corrects its own block 

The block claimed the fixture had verified that "replicas stay converged
--- the op IS broadcast". That was inspection of the call sites, not
execution: nothing had ever replayed the op on a replica, and text
equality alone cannot see a lost version advance. It also called the
buffer-end range location "genuinely arbitrary either way"; the census
rules it, and finds it weakly preferable.

Both corrections are recorded in place rather than quietly dropped,
along with what each review round caught and the two mutation
asymmetries the framing asserts.
This commit is contained in:
Levi Neuwirth 2026-08-30 17:56:05 +02:00
parent db24ae3010
commit 96bf2c3dfd
No known key found for this signature in database
1 changed files with 45 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

97
docs/active-work.md
View File

@ -301,66 +301,59 @@ waits for a signal that is not coming.
- **THE FIRST DISPATCH IMMEDIATELY FOUND A RED ON `main`**, which is - **THE FIRST DISPATCH IMMEDIATELY FOUND A RED ON `main`**, which is
what this lane was built for. See the proptest entry below. what this lane was built for. See the proptest entry below.
## CRDT identity-replace undo — the proptest invariant may be MIS-SCOPED — NEEDS A LANE ## CRDT identity-replace undo — LANE TAKEN, PR #246 OPEN
**CORRECTION.** An earlier version of this entry called the dispatched **Branch `crdt-identity-undo`, based on `aae5b35`; implemented at
run's red "a DETERMINISTIC red" and "not like anything else in this `db24ae3`.** Framing `docs/crdt-identity-undo-framing.md`, **APPROVED at
registry — a property violation with a concrete witness, not a load revision 4** after four review rounds. Gate green **head-exact**, all 8
artefact", and proposed committing the proptest seed as the first stages, log `20260830T154827Z-2907414`; `HEAD` and
step. **All of that was wrong**, and it was wrong because I recorded a `git status --porcelain` identical before and after.
finding without checking whether `main` already documented it.
**It is a randomly sampled recurrence of known #157 behaviour.** **The decision, ruled:** a visible TEXT delta and a CRDT-VERSION delta
`src/buffer.rs:3005` carries an `#[ignore]`d deterministic fixture, are **independent dimensions** of `Edit`. The invariant is narrowed to
`crdt_undo_of_an_identity_replace_reports_a_no_op_edit_carrying_an_op`, key on **provenance**, not shape — a forward version-only edit must
which reduces this exact case and records its mechanism: still carry no op (and still cannot produce one, because the three
syntactically empty `EditOp` forms short-circuit at `is_no_op_edit`); a
history version-only edit may carry one, and must, or the version
advance the replicas need is lost.
1. the inserts produce `aaaaa `; **Two claims THIS BLOCK made are corrected by measurement:**
2. `Replace(5, 1, " ")` replaces the trailing space **with itself** — a
textual no-op but a real CRDT delete-plus-insert;
3. `Undo` therefore emits a **version-advancing CRDT operation with no
visible text change**, and `derive_replacement_edit` yields an empty
edit that still carries its `crdt_op`.
**Committing the seed is NOT the first step**, and proposing it was a - it said the fixture had verified that *"replicas stay converged — the
second error: it duplicates a deterministic fixture that already op IS broadcast"*. **That was inspection of the call sites, not
exists, and its only effect would be to make a disputed assertion fail execution.** Nothing had ever replayed the op on a replica, and text
permanently instead of occasionally. equality alone cannot detect a lost version advance — the drop-the-op
mutant leaves the text identical, and the failure that catches it
reads `version vector diverged undo`. C3 establishes convergence
properly, by seeding a replica with the forward ops first;
- it said the buffer-end range location was *"genuinely arbitrary either
way"*. **The §4 census rules it**: five consumers inert, three
permitted, none harmed — and for `TextView`, the one whose cost
depends on the location, the buffer end is the **cheapest** rebuild.
**What the fixture already verified**, so the lane does not redo it: **What the four review rounds caught, none of it by me.** Revision 1
content stays correct (rope and CRDT projection agree), replicas stay posed the decision instead of answering it, and its C3 passed its own
converged (**the op IS broadcast** — both `crdt_op` consumers read it drop-op mutant. Revision 2's C4 contradicted the implementation
unconditionally and neither short-circuits on an empty range), and the (`mark_stale` is unconditional and range-independent) and named two
cursor does not jump. consumers out of six. Revision 3's C4 claimed guard mutations that
**survive** — at the buffer end, deleting the fold or style guard
changes nothing — and its C9 guarded a file set and a count, which a
same-file substitution walks straight through.
**THE ACTUAL DECISION** is whether a **visible text delta** and a **15 mutation checks were run, each on a clean tree and reverted.** All
**CRDT-version delta** are independent dimensions of `Edit`. The behaved as the framing predicted, including the two asymmetries the
proptest's invariant assumes they are the same dimension. It was framing states rather than assumes: C2b is **masked** for the Insert and
written for the FORWARD `apply_edit` short-circuit, which returns Delete forms by their defensive early returns (`buffer.rs:1177`,
before producing an op at all — and **CRDT-mode undo/redo never reach `:1192`) and **dies** for Replace, which has none; and C4b **survives**
that path**. the style-guard deletion, which is why C4c injects an INTERIOR empty
edit where the fragmenting is reachable.
**What the lane owes as evidence:** **Deliberately not done:** the proptest regression seed is NOT
committed. It duplicates a deterministic fixture and would make a
disputed assertion fail permanently rather than occasionally.
- **forward textual no-ops still produce NO operation** — whatever the **It does NOT reorder the roadmap.** GUI arc 1b remains the next product
resolution, the short-circuit the invariant was actually written for lane per `COHERENCE.md` §20.
must keep holding;
- **any permitted empty-text undo operation carries valid bytes and
preserves remote replay convergence** — permitting the shape must not
become permitting a malformed op;
- **an explicit disposition of the arbitrary artifact**:
`derive_replacement_edit` reports the empty range at the **buffer
end** rather than at the edit site. The fixture calls this genuinely
arbitrary either way; the lane must say which it is choosing, not
leave it unexamined.
**Un-ignoring that fixture is the first step of whichever resolution
wins**, as its own doc comment says.
**Why it is worth a bounded interruption:** a mis-scoped property can
now randomly redden `main`, and the dispatched run proved it. **It does
NOT reorder the roadmap** — GUI arc 1b remains the next product lane
per `COHERENCE.md` §20's priority order.
### Superseded lane state, kept for the record ### Superseded lane state, kept for the record