Iter 17. Lands the BFLD JSON wire spec format for rf_signature_hash —
a "blake3:" prefix followed by 64 lowercase hex chars. Replaces the
default serde array-of-integers encoding which was unusable for
downstream consumers (HA, Matter, MQTT).
Added (in src/event.rs):
- ser_rf_signature_hash<S>(hash: &Option<[u8;32]>, s) custom serializer
- Field attribute on BfldEvent.rf_signature_hash now uses
serialize_with = "ser_rf_signature_hash" alongside skip_serializing_if
- nibble_to_hex(u8) -> char private const fn (no `hex` crate dep needed
for 32 bytes; lowercase hex is trivial)
- Output format: "blake3:deadbeef..." exactly 71 ASCII chars
tests/json_hash_format.rs (5 named tests, all green):
rf_signature_hash_serializes_as_blake3_prefixed_lowercase_hex
(expected hex built programmatically via format!("{b:02x}"))
hex_string_is_always_64_chars_when_present
(parses the JSON, isolates the hash substring, asserts exact 64
chars and lowercase-only — catches case-folding regressions)
hash_field_omitted_entirely_when_none
end_to_end_emitter_hasher_to_json_emits_blake3_hex_hash
*** Cross-iter integration test: BfldEmitter::with_signature_hasher
→ SensingInputs.rf_signature_hash = None → emit derives via
BLAKE3 → BfldEvent::to_json → contains "blake3:" prefix.
Spans iters 13, 14, 15, 16, 17 in a single assertion. ***
end_to_end_restricted_class_omits_hash_even_with_hasher_set
(class 3: even with hasher installed, JSON omits the hash)
ACs progressed:
- BFLD wire spec §6 — rf_signature_hash JSON shape now matches the
documented format ("blake3:..."); HA / Matter consumers can parse
it without custom byte-array decoding.
- ADR-118 §1 invariant I3 — visibility: the JSON wire form now
cryptographically tags the hash with its algorithm prefix, so
consumers can verify they're not parsing a different (weaker)
hash that a future PR might accidentally substitute.
Test config:
- cargo test --no-default-features → 72 passed (json_hash_format cfg-out)
- cargo test → 128 passed (123 + 5)
Out of scope (next iter target):
- IdentityFeatures typed encoder so callers feeding BfldEmitter don't
need to know that embedding bytes serve as hasher input.
- Replace the manual hex push with `hex::encode` if/when the workspace
takes on the `hex` crate dep for other reasons; current path saves
the dep without sacrificing correctness.
Co-Authored-By: claude-flow <ruv@ruv.net>
29f23cb97e