Migrating to 0.5.0

Receiving boundaries and JSON certificates now enforce a full Contract(a). A Definition(a) continues to describe structural acceptance, decoding and JSON Schema generation. Its API and structural semantics are unchanged.

Structural-only contracts

Wrap a definition with contract(definition) when constructing a boundary or calling verify. No semantic checks are added. JSON-only verification continues to skip conversion callbacks in this case.

forward, forward_json and verify now return ContractError on rejection. Structural failures are wrapped in Structural(errors). Semantic failures are reported separately in Semantic(failures).

Semantic requirements

require(contract, description, check) appends a check of decoded a returning Result(Nil, List(Violation)). Checks cannot transform the value. They must be pure and total, with immutable captured context. Checks run once in declaration order after structural success; normal failures are collected. Exceptions remain operational failures.

decode_contract returns decoded data after all checks pass. validate_contract and verify decode once if checks exist, then discard decoded data. A typed boundary passes that already checked decoded value to its handler.

Inspection and documentation

boundary_contract, json_boundary_contract and verified_contract expose the full contract. Existing *_definition accessors remain structural accessors for schema generation. contract_requirements returns descriptions in declaration order; documentation.render_contract includes them after structural HTML.

Generated JSON Schema describes the underlying definition only. Semantic checks are additional acceptance conditions, not schema keywords. Requirement prose records intended behavior; it does not prove that a check implements that prose. VerifiedJson(a) retains the exact contract and original JSON, not decoded a. The type parameter does not identify particular constraints or captured context.