json-schema-codec-generator

JSON-Schema Codec Generator

Generate typed codec validator code from collections of inter-related json-schema

Generate typed codecs from collections of json-schema using the included library or the bundled CLI.

• Supports collections of schemas having $references between one-another.
• Produces type-safe validator functions via ajv.
• Designed for code-generation to maximize runtime performance.

Installation

To install the CLI, the recommended approach is to install it globally.

npm install -g json-schema-codec-generator

Alternatively, you can use npx to install and run it on-demand.

npx json-schema-codec-generator --help

CLI Usage

Given a folder full of .json files containing JSON-Schema definitions in ./path/to/my/schema/dir, the following will produce:

• ./codecs/index.js -- JavaScript code that exports a ValidatorFunction<T> function for each discovered schema. These functions have no runtime dependencies and thus can be used in any JavaScript runtime.

  Each Schema passed in will have a corresponding ValidatorFunction generated.

• ./codecs/index.d.ts -- TypeScript definition files for the generated codecs. These type definitions ensure that code consuming the codecs will benefit from compile-time and edit-time type hinting.

json-schema-codec-generator --input ./path/to/my/schema/dir --output ./codecs/

ValidatorFunction

export interface ErrorObject {
  instancePath: string;
  message?: string;
  data?: unknown;
}

export interface ValidatorFunction<T> {
  (obj: unknown): obj is T;
  errors?: ErrorObject[];
}

For a given schema named Bookmark, a validator function named validateBookmark of type ValidatorFunction<Bookmark> will be exported as well as a Bookmark type. These functions can be used as type assertions. Immediately after calling a validator function and seeing a validation failure, the validation errors can be recovered from validateBookmark.errors.