Append mqtt_neighbors_enabled(u8) + mqtt_neighbors_interval(u32) to the
observer tail of MQTTPrefs. The layout is kept byte-identical to the flex
neighbors build: the enable flag lands in the old struct's zeroed trailing
padding (offset 2857) and the interval begins exactly at the former baseline
(2860), so sizeof grows 2860 -> 2864 (net +4 bytes). offsetof static_asserts
lock the layout so a mismatch fails the build.
The codec now accepts three v1 payload sizes: register 2860 as a
"pre-neighbors" Current payload so an in-lineage upgrade reads its existing
/mqtt_prefs and defaults the neighbors tail (off / 24h). Because 2864 is the
shared Current baseline, a /mqtt_prefs written by either the flex build or this
firmware is interchangeable.
Add the 12/24/336h interval constants, neighbors defaults, and a load-time
interval clamp that keeps persisted values inside the signed-delta millis()
scheduling window. Extend the host codec suite with a pre-neighbors migration
case and neighbors round-trip coverage.
Rework the /mqtt_prefs load/save path so preference migrations are
crash-safe and, for the first time, unit-testable on the host.
Most of this is extraction. The multi-format migration that previously
lived inline in CommonCLI.cpp (and could only run on-device) is moved
into three dependency-free headers so it can be exercised without
Arduino, a filesystem, or the radio stack:
- MQTTPrefsStorage.h frozen layout structs for every /mqtt_prefs
format ever shipped, with static_asserts that
fail the build if any on-flash offset changes.
- MQTTPrefsCodec.h pure format classification, field-copy
migration, and plausibility validation.
- MQTTPrefsAtomicStore.h transactional writer plus the power-cut
upgrade gate, both host-testable.
New behavior, beyond the refactor:
- Atomic writes: /mqtt_prefs is written to /mqtt_prefs.tmp, verified,
then published with an atomic rename; the writer never removes the
existing file. A failed or interrupted save leaves the current
config intact.
- Power-cut ordering: LegacyUpgradeGate guarantees /mqtt_prefs is
durably committed before the legacy /com_prefs (or /node_prefs)
carrying the observer tail is compacted or removed, so an
interrupted two-file upgrade retries on the next boot without
losing settings.
- Corrupt, unsupported-version, and newer-than-known files are
preserved and the device boots on in-RAM defaults, rather than
overwriting a file this firmware cannot fully decode.
- Headerless legacy formats are validated for plausibility before
they are trusted and rewritten (raw prefs carry no checksum).
The full historical format matrix is migrated forward to the versioned
v1 layout: pre-slot (including pre-wifi-power), 3-slot (base and
token/topic tails), and headerless 6-slot (base, audience, rx, ntp).
Scope note: only /mqtt_prefs and the one-time /node_prefs -> /com_prefs
name migration use the atomic path. Ordinary /com_prefs saves remain a
direct rewrite, unchanged by this commit.
Tests: adds two host GoogleTest suites (pio test -e native).
- test_mqtt_prefs_codec: format classification, migration fixtures,
v1 header integrity, downgrade preservation.
- test_mqtt_prefs_atomic_store: transactional writes, short-write
detection, begin/finish/rename failure cleanup, original-file
preservation.
agessaman