Review round 2, P1. Undo could empty the "read-only" snapshot.
`render_snapshot` wrote with bypass_intercept, which leaves ordinary
undo history behind, and `Buffer::undo` reaches the rope through
`ensure_writable` without ever consulting the intercept chain. So a
single `C-/` — or `M-x buffer.undo`, which needs no keymap at all —
replaced a freshly rendered snapshot with an empty buffer.
`set_round_trip_input` does not help: it routes the key into the daemon
command path, which is exactly where undo runs.
Rebinding the undo chords buffer-locally would not have closed this,
and `compile.lua` already says so in a comment: "command/menu undo
stays dispatchable". `*compilation*` and listview panels therefore
carry the same latent defect today.
Adds `Buffer::set_generated_contents` (Lua:
`pmacs.buffer.set_generated_contents`): lift `read_only`, replace the
contents skipping intercepts, discard the resulting history, re-assert
`read_only`. This ships the framing's deferred immutability lane as ONE
primitive rather than exposing the setter — a bare `set_read_only`
would let a caller lock a buffer it can no longer refresh, which is
precisely why that lane was deferred. Discarding history is
load-bearing twice: it removes what undo would replay, and it stops a
periodically refreshed buffer accumulating rope clones that `read_only`
guarantees nothing can ever pop.
New acceptance 16c drives the real M-x path
(`command.invoke_interactive`), the chord, and redo, and asserts the
owner's own refresh still works — the operation plain `read_only` would
have broken. Acceptance 16b flips from asserting `is_read_only()` is
false to true, because the property it documented is the one that was
wrong. Three `buffer.rs` unit tests cover the primitive directly,
including that ten refreshes leave an empty undo stack.
Bite: restoring the delete+insert render reproduces the report exactly
— `left: Some("")` against the full snapshot — failing 16c and 16b.
Still open, and now named in the framing, COHERENCE.md §14 and the
ledger: `*compilation*` and listview have not adopted the primitive and
remain emptiable by `M-x buffer.undo`; a streaming-friendly variant is
needed for the append case. In CRDT mode `read_only` is what refuses
undo, since loro's UndoManager exposes no clear through `CrdtState`.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016gGQC6eqHJVbZJ5Hg7aLer
Levi Neuwirth
8c5b39ef32