Kubb v5.0.0-beta.104

Appearance

AST ​

Kubb's universal Abstract Syntax Tree is the contract between the two halves of the pipeline. Adapters produce the AST from a specification (OpenAPI, AsyncAPI, JSON Schema, and so on), and plugins consume it to emit files. Because every plugin reads the same tree, one plugin works against any spec a custom adapter supplies.

The tree shape ​

A single InputNode sits at the top, holding reusable schemas and operations. Operations point at parameters, an optional request body, and responses. Each of those connects back to schemas.

InputNode
├─ schemas: SchemaNode[]
└─ operations: OperationNode[]
├─ parameters: ParameterNode[]
├─ requestBody: RequestBodyNode
└─ responses: ResponseNode[]

A SchemaNode is discriminated by its type, which falls into one of three groups.

Structural
objectarraytupleunionintersectionenum
Scalar
stringnumberintegerbigintbooleannullanyunknownvoidnever
Special
refdatedatetimetimeuuidemailurlipv4ipv6blob

Request bodies and responses hold one ContentNode per content type (for example application/json), and each content node carries its own body schema.

  • Every child slot is a node, so a single traversal drives both transform and collect across the whole tree.
  • Every node also carries a kind field as the discriminant, so switch (node.kind) narrows the type for you.

Spec-agnostic by design ​

A plugin never looks at OpenAPI directly. It reads the tree the adapter produces, which is why the same plugin works for OpenAPI 2.0, 3.0, 3.1, and any custom adapter you write.

How the AST connects the pipeline ​

The same tree flows through four stages, each documented on its own page:

  • Adapters build the AST from a spec.
  • Plugins read it and emit files.
  • Macros rewrite nodes before printing.
  • Parsers turn the emitted nodes into source code.

NOTE

Import the ast namespace and its factory node builders from kubb/kit, alongside definePlugin and defineGenerator. Everything on this page, including the guards, the macros, the printer, and the visitors, comes from that same namespace. See the Kit API reference for the full list.