common-schemas

Decentraland data structure interfaces and validators for TypeScript-based projects.

Install it with:

npm i @mtv/schemas

Design Guidelines

• Prevent type problems across projects
• Fail as early as possible, aim for compile-time
• Preserve user optionality through runtime helpers
• Prefer no-cost implementations and allow no-dependency import
• Code is written once, read hundreds of times

Implementation decisions:

• The main entrypoint should only export types
• Every type is also a namespace
• Type names are PascalCase
• Validators and schemas are camelCase

Collaborator's Guide

Generating types, validators and schemas

This library export types that also act as values. This is achieved through TypeScript's namespaces. This means that every type imported from this library can also be used as a JS object. These types will include two properties named schema and validate. namespaces in typescript can be considered "cost imports".

Example Type Definition

// Declare type
export type MyType = {
  value: number;
};

// Declare namespace for the type
export namespace MyType {
  export const schema: Schema<MyType> = {
    type: "object",
    properties: {
      value: { type: number },
    },
    additionalProperties: false,
    required: ["value"],
  };

  export const validate = generateValidator<MyType>(schema);
}

MyType can now be both used as type const a: MyType or as an object MyType.validate(a).

Beware that validate has type ValidateFunction<T> which ajv creates automatically. When writing new validations always try to implement it as an ajv validation, even if custom code is needed. See here.

Particularly, beware of using the library like this, because reports by the validator.validate function are lost and never returned to the caller.

const validator = generateValidator<MyType>(schema);
export const validate = (mt: MyType) =>
  validator.validate(mt) && otherValidations(mt);

Code ownership

Please add types and schemas of your domain into the src/<team> folder, also add your team to the CODEOWNERS repository to make sure nobody accidentally changes it without your team noticing it.

Informing changes

Please notify about changes to the schemas to relevant teams by adding the whole team (i.e. @mtv/dapps) as reviewers of the pull requests.

It is recommended to subscribe to this repository (using the Watch function) if you use any internal part of the Decentraland ecosystem.

Making changes

To make sure the relevant persons and groups are aware of changes in these types, there's an api-extraction process executed with https://api-extractor.com that creates a report file for review between commits. It gets included as part of PRs for easier read.

To generate the file before submitting a PR, run npm run refresh-api. This is executed by the CI by runnig npm run check-api. It also verifies that the generated file matches the exported types.

Versioning and Publishing

Versions are handled manually using Github releases and semver.

Main branch is automatically published to the @next dist tag to test integrations before final releases happen.