ADR 0121, first half. The `mesh-*` seats said who does a job and nothing about what
may be said to them or by them, so the mesh had roles it could not describe. They
take the same three fields a module's seat has now, and the machinery that already
derives a work queue, a holder's worker and a permission set from a declared seat
does it for these too.
The build-machine role accepts a build and emits an outcome, so `mesh.build.request`,
`mesh.control.built` and the BUILDS stream are gone. A work queue shared by several
build machines is what a seat's `accepts` already is, and keeping a second mechanism
for it was two places a permission could be wrong.
The controller's own side of a seat is a named list rather than something derived: it
is not a module and declares no `uses`, so which roles the mesh itself submits work to
has to be stated — and stating it makes that question answerable.
Two things this caught:
**The followed event subjects were hard-coded and had just gone stale.** They were
written out while the catalogue still spelled its events as the old bus's routing keys,
so converting those (issue 127) turned the pair into a controller listening to a
subject nothing publishes — the same fault as the issue, from the other side. They
derive from the emitter and the event name now, through the same function the
permission uses, so the two cannot drift apart.
**A role's queue exists before its holder**, checked against a real server, and
asserting twice changes nothing. Work queues until somebody arrives to do it, so
assigning a build machine later flushes the backlog instead of having lost it.
Issue 127 stood because nothing compared the two halves. Every manifest was
well-formed on its own and every derivation correct on its own, and no
cross-module subscription in the mesh matched anything — a subscription that
matches nothing is not an error, it is silence.
Two checks, because the mistake is possible at two scales.
Per manifest: an event is a local name, and `module.` is refused with the name to
write instead. A module emitting under what reads as another module's name is
refused too, pointing at the seat, where a name outlives whoever holds it.
Across the catalogue: where a consumed event's emitter is present, it must emit
that event. It cannot demand a live emitter for everything — a module lives in its
own repository and may be installed long before the one whose events it wants — so
the rule is narrower and still catches this. It found two real dangling
subscriptions the moment it ran.
Wildcards were undecided and two manifests needed them: `*` is one name and `**`
is the rest, spelled the mesh's way and derived to `>` here and `#` on the old bus.
A manifest naming either would stop being true when the wire changed, which is the
whole reason names are local.
And the field documentation taught the old form, examples included — which is why
the drift was uniform across 37 manifests rather than scattered. Nobody was
guessing; everybody followed the comment.
The derivation had nothing feeding it. `BusRecords` reads what it needs — the
machines, what each runs, every manifest, and which machines hold a live token —
and turns it into the records the composer derives from.
**A module's authority comes from its manifest, not from its assignment.** The
assignment says where it runs; what it may say is what it declared. So the two are
read together and the manifest decides, which is also why a seat's protocol is
gathered across the whole catalogue rather than from one manifest: a seat is
declared by one module and held by another, and that is the whole reason a seat
exists.
Three things checked against a real store, each a user that would be wrong in a
way nothing reports:
- A module assigned to a machine becomes a user with exactly the authority it
declared, including the protocol of a seat some *other* module declared — a
module granted nothing on a seat it was assigned to send to would fail on its
first publish with an authorisation error that says nothing about a seat.
- Only a machine holding a live token gets an enrolment user. One outliving its
token is a right to join that nobody issued.
- A module assigned and absent from the catalogue is refused rather than composed
with an empty permission list. The catalogue already refuses to forget an
assigned module, so this is the second line — and it earns its place there,
because relying on another package's invariant is how a rule ends up enforced by
nothing.
People are left empty rather than guessed at: the account model is built and
`operator issue` is not, so there is nobody to derive yet.
jschoubben