feat(component): ComponentSession handle over the WIT resource session#175
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Phase 2 foundation for the boundary redesign (rustfava #173). Wraps the rustledger `resource session` (shipped in v0.16.3): `open_session(source)` / `open_session_file(path)` return a `ComponentSession` that holds the booked ledger inside the component, and `info`/`query`/`filter`/`clamp` run against the held ledger server-side — no source re-parse, no directive list shuttled across the FFI. Each session owns its own wasmtime store/instance (the resource handle is bound to them), so a file session keeps its WASI pre-open and sessions don't contend on a shared store; file sessions map `/work` guest paths back to host paths in `info()`. This is the engine capability; wiring Fava's loader/query/filters to hold and reuse a session (replacing `_entries_to_source` + the clamp dict round-trip) is the next step. Tests cover query/filter/clamp on a held ledger and host- path resolution for file sessions. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This was referenced Jun 18, 2026
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Phase 2 foundation for the boundary redesign (#173). Wraps rustledger's
resource session(shipped in v0.16.3, rustledger beancount#1421).What
RustledgerComponentEngine.open_session(source)/open_session_file(path, …)return aComponentSessionthat holds the booked ledger inside the component.session.info()/query(q)/filter(begin, end)/clamp(begin, end)run against the held ledger server-side — no source re-parse, no directive list marshalled across the FFI per call./workguest paths back to host paths ininfo().Why
This is the engine capability that lets Fava stop re-parsing source for queries (
_entries_to_source) and stop round-tripping directive lists through_unmarshalfor clamp — the root of the shape-drift bug class.clamphere runs on the held core directives, so cost basis survives with noWIT→core→WITround-trip.Scope
Engine capability + tests only. Wiring Fava's
loader/query/filtersto hold and reuse a session (the part that deletes_entries_to_sourceand the clamp dict path) is the next step in #173. ruff + mypy clean; 16 component tests pass (incl. newopen_session_*tests covering query/filter/clamp on a held ledger and host-path resolution).