Round 1 review, four P1s. All real; the first two mean the fallback did
not work at all.
**1. The latch swapped the config but never spawned or re-attached.**
Nothing re-fires an attach on a config change and `attach_buffer`
early-returns for a live attachment, so the buffer stayed bound to the
server that had just been stopped. The user got a config edit and no
language server. `fire_latch` now rebuilds through a new
`pmacs.lsp._attach_buffer` export.
Two mechanics had to be right for that rebuild to happen at all:
* It is **retried on the tick**, because `pmacs.lsp.stop` leaves the
state `shutting-down`, which `server_is_live` counts as LIVE — an
inline re-attach early-returns the stale record and the swap is a
silent no-op.
* The latch **does not stop an already-terminal server**, and this is
a substrate bug worked around rather than a style choice.
`LspManager::stop` on a `Crashed` client takes its not-initialized
branch, terminates the dead process, and sets `ShuttingDown { ..
None }` on the premise that "the next exit observation cleans up" —
but the exit already happened, which is what made it `Crashed`. No
further event arrives, so the client is stuck in `ShuttingDown`
forever: `server_is_live` reads it as live so `attach_buffer` never
rebuilds, and `forget` refuses it for not being terminal. Stopping a
dead server is what makes it un-replaceable. Named in framing §6; the
fix belongs in `stop` and changes behavior for every language.
**2. A missing `lake` bypassed probe and latch entirely** — the single
most likely real failure. `ensure_server` swallows a synchronous ENOENT
and returns nil, so there was no attachment, and the hook keyed on
`active_attachment()` returned before arming anything. The hook now keys
on the buffer's LANGUAGE and treats a Lean buffer with no attachment as
the failure itself.
**3. `waitForDiagnostics` omitted `version`.** Lean's
`WaitForDiagnosticsParams` is `{ uri, version }` (v4.9.0,
`src/Lean/Data/Lsp/Extra.lean`); the request is how a client says which
revision it wants. It looked correct only because the fake server echoes
any payload — so the fake server now validates and returns InvalidParams
without it.
**4. The ledger stated the dangerous stacking order** in one sentence
and the correct rule in the next. Fixed to say BEFORE. A safety rule
written twice with opposite senses is worse than not written.
Also (P2): the probe/latch suite now drives the production path —
`buffer.after-load` -> ticks -> probe drain -> latch -> re-attach — with
real executable stubs, and asserts the originally opened buffer ends up
on a LIVE server. Round 1's acceptance 36 asserted every server was
terminal, i.e. pinned the ABSENCE of the fallback it claimed to test.
`M.fallback` is a table so the suite can point it at a working stand-in;
the probe now spawns `cfg.command --version` rather than a hardcoded
`lake`, which is also more correct for a user who configured a wrapper.
`swap_to_fallback`'s `command ~= "lake"` guard is gone: the latch fires
only when the configured server actually failed, one visible fallback
beats no server, and `probe.latched` is what keeps it to exactly one.
Three new bites, all against the committed tree: no re-attach after the
swap -> three latch tests fail; hook keyed on the attachment -> the
missing-`lake` case fails; `waitForDiagnostics` without `version` ->
acc37 fails with the server's InvalidParams.
Framing Q#LN7, Q#LN8, Q#LN16; acceptance 22–28, 24a/24b, 35, 36, 36a, 37.
Stacked on Stage 3a (#167), whose notification/response seams and
`pmacs.fs.canonicalize` this consumes. No protocol change; the only Rust
outside the test helper is one `include_str!` line.
**The Lake-aware root (Q#LN8).** `pmacs.project.detect` cannot express
this rule — it is innermost-wins by construction, and a Lake package's
`lean-toolchain` sits at the outermost level, so a file under
`<pkg>/.lake/packages/dep/` belongs to `<pkg>`'s server rather than
`dep`'s. The resolver walks up collecting markers and returns the
outermost, stopping at `pmacs.project.search_boundary()` so a stray
marker above a fixture cannot leak in.
Two things about the marker test are easy to get wrong in opposite
directions, and both are pinned. `io.open` **succeeds on a directory**,
so a truthiness check accepts a `lean-toolchain` directory; but
requiring a non-nil read rejects an **empty** `lean-toolchain`, which is
a legitimate marker — `locate-dominating-file` semantics are existence,
not content. The discriminator is `read`'s second return: decline only
on a non-nil error. Acceptance 24a and 24b each fail against the
implementation that satisfies only the other; both bites are recorded.
The root is canonicalized once up front, because a configured root
reaches `file_uri_for` verbatim and that URI is the affinity key (#161).
Canonicalizing the starting directory suffices — every ancestor of a
canonical path is canonical, since the walk only strips components.
**`lake serve` with a lazy probe and a one-shot latch (Q#LN7).** Nothing
runs at init: `pmacs.lsp.config` is declarative, and spawning a process
at startup for every user, Lean-using or not, is the cost rev 1 refused.
Both the probe and the server spawn are gated on a real Lean attachment.
The probe cannot gate the first attach — there is no blocking process
run, so its verdict arrives after `ensure_server` has already decided.
Hence the optimistic spawn, with the probe and latch correcting it. A
non-zero probe exit is deliberately NOT a trigger: §2.9's elan-shim case
makes `lake --version` fail on machines where `lake serve` still works,
and the server-failure latch covers that better. The probe answers only
the question failure detection would answer slowly — an old-but-working
lake that starts a useless server.
The latch stops the failing server **before** spawning the fallback, and
that ordering is load-bearing rather than defensive: the spec default is
`OnCrash`, the termination handler never consults the exit code, and
`maybe_restart` has no attempt ceiling, so a broken `lake` respawns
forever underneath the latch. `pmacs.lsp.stop` sets `restart = Never`,
which is what disarms it. Bitten: removing the stop fails acceptance 36.
The swap rewrites `command` and `args` only, so a user's `env`,
`settings`, `init_options` and `root` survive — a wholesale table
replacement would discard their `init.lua` at the moment they are least
likely to notice.
**`waitForDiagnostics` (Q#LN16)** resolves through Stage 3a's response
seam, with `M-x lean.wait-for-diagnostics` on top. `$/lean/fileProgress`
subscribes on the notification seam and is pinned end-to-end through a
new `leanprogress` mode on the fake server rather than by calling the
handler directly — the wiring is the only part that can break.
**Attribution (COHERENCE §9/§1.2).** The probe spawns as
`lean:lake-version-probe`, so a user wondering why their editor touched
`lake` finds an owner in `pmacs.process.list`. The latch reports through
`pmacs.editor.set_status` — the channel that exists — and acceptance 36a
observes that channel, so a report made only through the undefined
`pmacs.error` would fail it.
**Stage 1's acceptance 12 is updated, half superseded.** It asserted
`pmacs.lsp.config.lean4 == nil` to guard against a Stage-3 front-run;
Stage 3b is that stage, so keeping it would pin the opposite of the
intended behavior. The half that survives is the one about restraint,
and it matters more now: constructing an editor spawns nothing even
though the config exists and names `lake`, and opening a Lean buffer
with no server configured spawns nothing either. That is what holds
Q#LN7's "not at init" promise.
Bites recorded, all against the committed tree: bare `io.open` -> 24a
fails, 24b passes; require-non-nil-read -> 24b fails, 24a passes; no
canonicalization -> the symlink case spawns two servers; no stop before
fallback -> acceptance 36 fails.
Levi Neuwirth