Spec: Add Missing SCXML System Variables

Status: done Priority: P1 Created: 2026-02-08 Completed: 2026-02-08 Owner: AI

Context

The W3C SCXML spec (Section 5.7) requires several system variables that this library doesn't expose in the data model:

. _sessionid - Session ID bound at load time. Currently tracked internally (::sc/session-id) but not in the data model. Accessible via env/session-id function but not as a data model variable.

. In() predicate - Section 5.9 requires all data models support this. The functionality exists (runtime/current-configuration) but isn't exposed as a predicate in the execution environment. Additionally, environment.cljc has an In alias for is-in-state? but it requires the env parameter — not the same as the spec's zero-context In(). Write an In(state) helper that returns a function. Put it in the elements namespace.

. _name - Statechart name attribute. Exists on chart but not exposed in data model.

Be careful of circular references. You might need to simply destructure data manually.

Requirements

. Bind _sessionid in data model during initialization (v20150901_impl.cljc:820) . Provide In predicate accessible from expressions without explicit env . Optionally bind _name (low priority) . None of these should be breaking changes

Affected Modules

• src/main/com/fulcrologic/statecharts/algorithms/v20150901_impl.cljc - Initialization
• src/main/com/fulcrologic/statecharts/execution_model/lambda.cljc - In() predicate
• src/main/com/fulcrologic/statecharts/data_model/ - Variable storage

Approach

Slice 1: _sessionid

Assign [:ROOT :_sessionid] during initialize! after session-id is established.

Slice 2: In() Predicate

Add In function to the data passed into elements.cljc

(defn In
  "Can be used as a shorthand as the sole value of the `:cond` (e.g. on if/transition elements)
   when using the lambda execution model."
  [state-id]
  (fn [{::sc/keys [vwmem] :as _env} & _]
    (boolean
      (some-> vwmem deref ::sc/configuration (contains? state-id)))))

Slice 3: _name (optional)

Lower priority, implement if straightforward.

Verification

. [x] In(:state-id) implemented in elements.cljc . [x] :_sessionid accessible from expression lambdas via data model . [x] :_name accessible from expression lambdas via data model . [x] Existing tests still pass (no regression) — 34 tests, 211 assertions, 0 failures . [x] New tests verify variable availability — 24 assertions in system_variables_spec.cljc