Step 4 of the BAST pivot: the layout engines, materializer, tunion
dispatch, and engine now consume the BAST typed tree (BastDoc/
BastStruct/BastField/BastType/...) instead of walking raw JSON with
get_alktype_kind*.
Breaking changes (per the pivot plan's semver contract):
- AlkTypeEngine::compile signature:
compile(schema: &mut Value, mode)
-> compile(bast_doc: &Value, root_name: &str, mode)
Drops &mut (BAST needs no in-place normalize_refs); adds required
root_name (D-BAST-001); input is a BAST document, not a custom-keyword
JSON Schema.
- OffsetMap::compute, LayoutBuilder::new, SequentialReader::new now take
a BAST document (&Value) + root_name (or &BastDoc) instead of a
v0.1.0 schema.
- tunion::read_byte_discriminator / read_field_discriminator /
resolve_variant / discriminator_size now take &BastUnion instead of
&Value.
- materialize::materialize_packed / materialize_aligned now take
&BastDoc instead of &Value.
Key design points:
- The engine stores a clone of the BAST Value + root_name so
sequential_reader() and read_field() can re-parse the typed tree on
demand without lifetime entanglement with the caller's Value.
- resolution is a single hash lookup via BastDoc::resolve_typeref;
no normalize_refs, no inline_union_variant_refs.
- bast.rs gains BastField::synthetic() (pub(crate)) for constructing
synthetic fields wrapping TypeRefs (array elements, record values,
union variants — these aren't fields and carry no field annotations).
- The v0.1.0 schema.rs helpers and validation.rs custom-keyword
validators remain defined (step 8 removes them). build_validator still
runs on the BAST doc — with no AlkType:* keywords present, the custom
factories don't trigger and jsonschema performs structural validation
only. The validate_bytes value-constraint enforcement (maxLength, enum
bounds) is step 5's concern (the BAST-native validator).
Tests:
- All engine, layout, materialize, tunion, and integration tests
converted to BAST format (kind/fields vocabulary, /
composition). Expected validation outcomes for the layout path are
identical; the maxLength/enum-bounds validate_bytes tests are step 5's
regression target.
- builder.rs::builder_chunk_header_compiles_in_packed_mode uses a
hand-written BAST doc (the builder still emits v0.1.0 format; step 7
converts it).
Verification:
- cargo test --release: 425 pass (348 lib + 77 integration)
- cargo clippy --all-targets -- -D warnings: clean
- cargo build --target wasm32-unknown-unknown --release: clean
- cargo doc --no-deps: clean
- New src/bast.rs: typed surface over a BAST document — BastDoc,
BastDef, BastDefKind, BastStruct, BastField, BastUnion,
BastDiscriminator, BastEnum, BastType, BastRef, BastArray,
BastRecord. Borrows from the source Value (no clone of the tree).
- $ref resolution is a single hash lookup against $defs
(#/$defs/<name> only); union variant refs resolved lazily via
BastDoc::resolve_typeref / resolve_ref — replaces
normalize_refs + inline_union_variant_refs (those stay for now;
step 8 removes them).
- Untrusted-input safe: every walk returns AlkTypeError::Schema on
a malformed document, never panic/unwrap (AGENTS.md §3).
Overflow-safe usize parsing via try_from (AGENTS.md §4).
- D-BAST-005 enforced: fields array only valid with field-name
discriminators; required for them.
- Additive only: new pub mod bast + re-exports in lib.rs. No
existing re-exports removed (those go in step 8). 47 new tests.
Verification:
- cargo test --release: 465 pass (379 lib + 86 integration)
- cargo clippy --all-targets -- -D warnings: clean
- cargo doc --no-deps: clean
- cargo build --target wasm32-unknown-unknown --release: clean
glm-5.2