Message-plane interface-description codegen¶

This chapter captures the requirements for the message-plane interface-description codegen toolchain: a layered set of crates that translates interface descriptions (today, CAN .dbc databases) into strongly-typed Rust message (de)serializers at build time, with a no_std, allocation-free, serde-free runtime (de)serialization path.

The decomposition is the message-plane twin of Device-driver codegen (the device-plane ESI toolchain) and CANopen device-driver codegen. Where the device-plane toolchains describe a device (identity + object dictionary + cyclic process image), this toolchain describes a message (the structs, enums, and request/reply services that cross a channel). The bounded message-type IR (taktora-idl-core (BB_0117)) is the peer of fieldbus-od-core:

Top-level umbrella feature — Message-plane interface-des... (FEAT_0110) — peer to Device-driver codegen toolc... (FEAT_0050) (EtherCAT device codegen) and CANopen device-driver codeg... (FEAT_0060) (CANopen device codegen). Build-time only; the only crate that links into a consumer at runtime is the wire runtime (serde-free no_std wire runtime (FEAT_0112)).
Capability-cluster sub-features — one per crate-layer concern, each :satisfies: Message-plane interface-des... (FEAT_0110).
Requirements — concrete shall-clauses that :satisfies: a capability-cluster feature.

This round delivers the DBC frontend and the CAN/wire backend end-to-end. OMG IDL and ROS 2 .msg/.srv frontends, and a J1939-PGN consumer of the generated types, are foreseen but out of scope this round; the architecture keeps them net-additive (see Anti-goals and cross-cutting traceability).

The umbrella decomposes into five capability clusters, each on its own page (see the toctree): the bounded message-type IR (Bounded message-type IR (FEAT_0111)), the serde-free wire runtime (serde-free no_std wire runtime (FEAT_0112)), the DBC frontend (DBC frontend (FEAT_0113)), the plane-generic codegen (Plane-generic codegen (FEAT_0114)), and the CAN/DBC backend (CAN/DBC backend (FEAT_0115)). The deliberately deferred anti-goals live on Anti-goals and cross-cutting traceability.

Top-level umbrella¶

Feature: Message-plane interface-description codegen FEAT_0110

status: implemented

is satisfied by: REQ_0958, REQ_0959, REQ_0960, REQ_0945, FEAT_0115, FEAT_0114, FEAT_0113, FEAT_0111, FEAT_0112

is refined by: QG_0024, ARCH_0081, ARCH_0082, ADR_0121

links outgoing: BB_0117, BB_0118, BB_0119, BB_0114, BB_0115

A layered set of Rust crates that consumes interface descriptions and emits strongly-typed message (de)serializers at build time. The toolchain is organised as layers that depend only leftwards:

IR core — taktora-idl-core: the bounded message-type IR (structs, enums, bounded sequences, services). std baseline. Knows no wire format, no DBC, no target language. The message-plane twin of fieldbus-od-core.
Wire runtime — taktora-idl-wire: the WireType trait the generated code implements, plus CAN signal bit-packing primitives. no_std, allocation-free, dependency-free, no serde. This is the only layer that links into a runtime consumer.
Frontend — taktora-idl-dbc: parses .dbc text into a typed model and lowers it onto an idl-core Module plus a physical-layout sidecar. Depends on idl-core.
Codegen layer — taktora-idl-codegen (naming policy, the MessageBackend trait, and resolve + generate; plane-generic, knows no wire format) plus taktora-idl-codegen-can (the one concrete backend this round, emitting WireType impls per the DBC layout).
Verification harness — taktora-idl-codegen-can-tests (publish = false): generates WireType code from a fixture DBC at build time and round-trips it.

The delivered slice is the IR plus the DBC frontend and CAN backend. Additional frontends (OMG IDL, ROS 2) and a J1939 consumer are net-additive follow-ons (see Anti-goals and cross-cutting traceability).

Requirements at a glance¶

Used filter:

ID	Title	Status	Satisfies
FEAT_0111	Bounded message-type IR	implemented	FEAT_0110
FEAT_0112	serde-free no_std wire runtime	implemented	FEAT_0110
FEAT_0113	DBC frontend	implemented	FEAT_0110
FEAT_0114	Plane-generic codegen	implemented	FEAT_0110
FEAT_0115	CAN/DBC backend	implemented	FEAT_0110
REQ_0945	NO runtime description parsing	rejected	FEAT_0110
REQ_0946	Boundedness is unrepresentable to violate	implemented	FEAT_0111
REQ_0947	Structural validation before sizing	implemented	FEAT_0111
REQ_0948	Plane-generic, policy-free IR	implemented	FEAT_0111
REQ_0949	WireType trait surface	implemented	FEAT_0112
REQ_0950	no_std, allocation-free, serde-free path	implemented	FEAT_0112
REQ_0951	CAN signal bit-packing primitives	implemented	FEAT_0112
REQ_0952	DBC parse to a typed model	implemented	FEAT_0113
REQ_0953	DBC lower to IR plus layout sidecar	implemented	FEAT_0113
REQ_0954	Deterministic naming policy with collision detection	implemented	FEAT_0114
REQ_0955	MessageBackend trait and resolve/generate entry point	implemented	FEAT_0114
REQ_0956	CAN backend emits WireType impls via the wire runtime	implemented	FEAT_0115
REQ_0957	Build-time generation proof-of-life	implemented	FEAT_0115
REQ_0958	NO additional frontends this round	rejected	FEAT_0110
REQ_0959	NO bool or float CAN fields this round	rejected	FEAT_0110
REQ_0960	NO J1939 application-layer consumer this round	rejected	FEAT_0110