The dispatch method was a single ~240-line switch of 34 cases, each
following the same pattern: decode params into some type P, call a
service method returning (R, error), wrap R in a result struct and
either marshalResultOrError-encode or return a raw rpc.NewError.
Adding a method was a 4-line ceremony per site, and grepping for
"methods banger speaks" meant reading the full switch.
New shape, in internal/daemon/dispatch.go:
- handler is the uniform `func(ctx, d, req) rpc.Response` type
every method dispatches through.
- paramHandler[P, R] is the generic wrapper that absorbs 28 of
the 34 cases (decode, call, marshal). No reflection — P and R
are deduced from the service-call literal, so each map entry
is a one-liner referencing a small adapter func.
- noParamHandler[R] is the decode-free variant for 6 methods
that don't carry params.
- rpcHandlers is the single source of truth for which methods
exist and which adapter they dispatch to.
- Four specials (ping, shutdown, vm.logs, vm.ssh) stay as named
`handler`-typed functions: ping/shutdown encode with raw
rpc.NewResult, vm.logs/vm.ssh need pre-service validation to
emit distinct error codes (not_found, not_running) that the
generic wrapper maps uniformly to operation_failed.
Daemon.dispatch shrinks from a 240-line switch to 11 lines:
version check, test-only handler short-circuit, table lookup,
invoke-or-unknown.
Tests:
- TestRPCHandlersMatchDocumentedMethods — keyset guard. Adding
or removing a method without updating the expected slice is a
red flag the test surfaces.
- TestRPCHandlersAllNonNil — catches nil-function registrations.
All pre-existing dispatch tests (param decode, error codes, etc.)
keep passing unchanged — the handler contract for any given
method is byte-identical from the RPC client's perspective. Smoke
(all 21 scenarios) exercises every code path end-to-end.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
