hsmc/CHANGELOG.md

Changelog

All notable changes to this workspace are documented here. The format follows Keep a Changelog and this project adheres to Semantic Versioning.

0.4.0 — 2026-04-28

Changed — observability (breaking)

• Unified observation pipeline. The codegen now emits a single __chart_observe! invocation per observable atom, dispatched at compile time to whichever sinks are enabled: the in-memory journal (feature = "journal"), defmt (trace-defmt), log (trace-log), and/or tracing (trace-tracing). All sinks share the same vocabulary by construction — the journal IS the observation stream; trace backends are textual renderings of it. With NO sink feature on, every call site expands to () (zero overhead). Multiple trace sinks may now be enabled simultaneously (previously they were mutually exclusive).
• Trace prefix changed. [ChartName] verb … → [statechart:ChartName] verb …. The new form is greppable and unambiguous in mixed log streams.
• Trace format is now logfmt-style. Every line is [statechart:Name] <verb> key=value key=value … (or native structured fields under tracing). Twenty verbs cover every TraceEvent variant — entries, exits (with begin/end pairs), actions (with kind), durings, transitions (with reason showing what triggered them), events (received/delivered/dropped/queued/failed), timers, terminate.
• trace; keyword deprecated. Still parsed for backwards compatibility, but no longer gates emission. Trace output is now controlled purely by which trace-* cargo feature you enable.

Changed — journal (breaking)

• TraceEvent::TransitionFired carries reason: TransitionReason. Replay consumers now see whether a transition was driven by an event (Event { event: u16 }), a timer (Timer { state, timer }), or internal logic (Internal).
• New TraceEvent variants for phase begin/end pairing.
  • EnterBegan { state } fires before a state's entry actions / timers / durings; Entered keeps its place as the end marker.
  • ExitBegan { state } fires before a state's during cancellations / timer cancellations / exit actions; Exited keeps its place as the end marker.
  • TransitionComplete { from, to } fires after a transition's full exit-then-enter sequence finishes; pairs with TransitionFired.
  • EventReceived { event } fires when an event is popped from the queue, before handler search; pairs with EventDelivered / EventDropped / TerminateRequested.

Added

• hsmc/tests/trace_format.rs — 11 tests pinning every verb's exact textual rendering, including a journal/trace atom-count equivalence test.
• TransitionReason enum — re-exported from the crate root when feature = "journal" is on. Carried on TraceEvent::TransitionFired.
• Multiple trace backends compose. Previously enabling more than one of trace-defmt / trace-log / trace-tracing was a compile error. Now they fan out independently.

Migration

Chart syntax is unchanged: every v0.1 / v0.2 / v0.3 statechart compiles under v0.4 without modification. Breakage is confined to the observability surface area:

1. Trace line prefix. Update grep patterns and log filters from [ChartName] to [statechart:ChartName]. The verb after the prefix is now a single hyphenated token followed by key=value pairs.

2. TraceEvent::TransitionFired has a new reason field. Update pattern matches:

   // before:
   TraceEvent::TransitionFired { from, to } => …
   // after:
   TraceEvent::TransitionFired { from, to, reason } => …
   // or, if you don't care:
   TraceEvent::TransitionFired { from, to, .. } => …
   

3. New TraceEvent variants. If you match exhaustively, add arms for EnterBegan, ExitBegan, TransitionComplete, EventReceived. Otherwise nothing changes.

4. trace; keyword is now a no-op. Charts that declared it still compile. Trace output is now controlled purely by which trace-* cargo feature you enable.

5. __chart_trace! and __chart_journal! macros are removed. These were doc-hidden and not part of the public API; mentioned here for codebases that grepped through the macro emission for patches/forks.

0.3.0 — 2026-04-27

Added

• journal Cargo feature. Records every observable atom of chart execution — Started, Entered, Exited, ActionInvoked (Entry/Exit/Handler), DuringStarted, DuringCancelled, TransitionFired, EventDelivered, EventDropped, EmitQueued, EmitFailed, TimerArmed, TimerCancelled, TimerFired, TerminateRequested, Terminated — into a Vec<TraceEvent> on the generated machine. Same chart + same events = byte-identical journal. Public API: journal(), take_journal(), clear_journal(), CHART_HASH (a stable FNV-1a fingerprint of the chart's structural definition).
• Root state targetable by chart name. on(Trig) => MyChart; resolves to the root state in both classify_target and resolve_transitions. From any nested state this is an up-transition (root is always on the active path).
• 113 deterministic-flow tests (under --features tokio,journal) comparing hand-built expected journals byte-for-byte against actual, anchored to spec sections: initial entry, lateral / self / up transitions, default-descent, event bubbling, timer arm / cancel / fire, emit, ordering, durings, step-vs-dispatch equivalence, root-targeting, current_state(), termination.
• verification/ workspace member with Creusot proofs. Verified mirrors of the runtime EventQueue and TimerTable carry creusot-std (Pearlite) contracts that Why3 + alt-ergo + z3 discharge mechanically. 14/14 VCs proven. just verify is self-installing (mise pulls opam + the pinned nightly + Creusot's canonical INSTALL).
• docs/002. hsmc-semantics-formal.md — canonical, unambiguous reference for chart behavior. Numbered S-rules supersede the v0.1 prose spec and v0.2 design-change-request.
• README "How a chart behaves" section — eight building-block rules that build on each other, with an explicit "what hsmc deliberately does NOT have" table.

Tooling

• mise.toml (root) declares stable Rust + components + embedded targets + cargo subcommands. verification/mise.toml declares the pinned nightly-2025-11-13 + opam + python venv + uv.
• set shell and set script-interpreter route every just recipe through mise exec — no shebangs, no per-recipe wrappers.
• just verify runs cargo creusot prove --no-cache so SMT invocations happen on every run; time shows ~7s CPU on ~1.2s wall = real parallel work.
• just mutants runs with --features tokio,journal so journal_* and det_* tests execute. 0 missed mutants.
• just miri excludes hsmc-macros (trybuild glob hits Miri's isolation) and hsmc-verification (different pinned toolchain). 66 tests pass under Miri, 0 UB.

Backward compatibility

Every v0.1 / v0.2 statechart compiles under v0.3 unchanged.

0.2.0 — 2026-04-22

Fixed — behavior-visible (breaking)

• Up-transitions no longer exit and re-enter the target ancestor. A transition whose target is already active (i.e., the target is on the path from root to the innermost active state, and the target is not itself the innermost) now unwinds only the subtree strictly below the target. The target's exit: / entry: actions do NOT fire, and its default(...) does NOT re-descend. You cannot re-enter a state you never left. The old semantics (exit target, re-enter, re-descend to default) was incorrect and could produce infinite re-entry when a child transitioned to its own parent. See spec §2.6, §T2.8, §T2.8b, §T2.8c.
• Self-transitions (target == innermost) are unchanged: the target is still exited and re-entered, timers still restart.
• Lateral transitions (target not on the active path) are unchanged.
• current_state() may now return a composite state when it became innermost via an up-transition.

0.1.0 — 2026-04-22

Initial release.

Added

• statechart! proc macro: declarative Harel-style hierarchical state machines with nested states, entry: / exit: actions, LCA-aware transitions, default-child descent, and terminate semantics.
• Typed event payload bindings: on(PacketRx { rssi: i16 }) => handler; expands into a typed handler signature, verified at compile time.
• Timer triggers: on(after Duration::from_secs(5)) => Next; and on(every Duration::from_millis(100)) => tick;, tracked in a fixed-capacity TimerTable.
• during: activities (v0.2 semantics): async functions that run while a state is on the active path and produce events. Multiple concurrent durings on a single state borrow disjoint &mut slices of the context, enforced by Rust's native split-borrow.
• Runtime: machine.run().await races active durings, the external event channel, and timer deadlines — one future, cooperative on embassy, multi-threaded on tokio.
• Feature gates: tokio (std + tokio runtime), embassy (no_std + embassy-time / embassy-sync). The two features are mutually exclusive and enforced via compile_error!.
• no_std by default; std pulled in only via the tokio feature.
• STATE_CHART const and dispatch() helper for introspection.
• Workspace: hsmc (library) and hsmc-macros (proc-macro front-end) both at 0.1.0.

Docs

• 320-line README.md with quickstart, semantics, and examples.
• Runnable examples: microwave and during_radio under tokio, embassy_full under embassy.
• Behavior, hierarchy, during, timer, and payload-binding test suites (13 integration tests).