TypeSpec Mappings

TypeSpec Mappings answer the practical question: when you write a TypeSpec construct, what does Typra generate?

Typra lowers TypeSpec into an internal contract AST before emitting targets. That AST preserves the details needed for runtime loading, saving, provider wire names, generated tests, and review metadata.

TypeSpec construct	Typra behavior
Models and properties	Generate target model surfaces with required, optional, and nested properties.
Arrays and records	Generate collection and dictionary-shaped fields using target-appropriate types.
String unions	Generate constrained enum-like runtime values, with optional parse aliases.
Open unions	Preserve known values while allowing target-specific open string handling.
Discriminated models	Generate polymorphic load/save dispatch using the discriminator field.
Interfaces and operations	Generate callable protocol/interface/trait-style seams from TypeSpec-native callable contracts.
Operation decorators	Add runtime cancellation, sync signatures, optional operations, effect metadata, and vectors to TypeSpec operations.
HTTP transport	Project TypeSpec HTTP path, query, header, cookie, body, status, success, and error semantics into producer and consumer seams.
Decorators	Add test samples, vectors, wire-name mappings, coercions, factories, defaults, and parse aliases.

The mapping pages use examples from Typra’s fixture contract so the docs stay aligned with exercised behavior.