This package includes a JSON schema for token lists, and TypeScript utilities for working with token lists.
The JSON schema represents the technical specification for a token list which can be used in a dApp interface, such as the Pegasys Interface.
Syscoin Token Lists is a specification for lists of token metadata (e.g. address, decimals, ...) that can be used by any dApp interfaces that needs one or more lists of tokens.
Anyone can create and maintain a token list, as long as they follow the specification.
Specifically an instance of a token list is a JSON blob that contains a list of ERC20 token metadata for use in dApp user interfaces. Token list JSON must validate against the JSON schema in order to be used in the Pegasys Interface. Tokens on token lists, and token lists themselves, are tagged so that users can easily find tokens.
The JSON schema ID is tokenlist.schema.json.
This package does not include code for token list validation. You can easily do this by including a library such as ajv to perform the validation against the JSON schema. The schema is exported from the package for ease of use.
The best way to manually author token lists is to use an editor that supports JSON schema validation. Most popular code editors do, such as IntelliJ or VSCode. Other editors can be found here.
The schema is registered in the SchemaStore, and any file that matches
the pattern *.tokenlist.json should
automatically utilize
the JSON schema for the supported text editors.
In order for your token list to be able to be used, it must pass all JSON schema validation.
If you want to automate token listing, e.g. by pulling from a smart contract, or other sources, you can use this npm package to take advantage of the JSON schema for validation and the TypeScript types. Otherwise, you are simply working with JSON. All the usual tools apply, e.g.:
import { TokenList, schema } from '@pollum-io/syscoin-tokenlist-sdk'
// generate your token list however you like.
const myList: TokenList = generateMyTokenList();
// use a tool like `ajv` to validate your generated token list
validateMyTokenList(myList, schema);
// print the resulting JSON to stdout
process.stdout.write(JSON.stringify(myList));Lists include a version field, which follows semantic versioning.
List versions must follow the rules:
- Increment major version when tokens are removed
- Increment minor version when tokens are added
- Increment patch version when tokens already on the list have minor details changed (name, symbol, logo URL, decimals)
Changing a token address or chain ID is considered both a remove and an add, and should be a major version update.
Note that list versioning is used to improve the user experience, but not for security, i.e. list versions are not meant to provide protection against malicious updates to a token list; i.e. the list semver is used as a lossy compression of the diff of list updates. List updates may still be diffed in the client dApp.
Once you have authored the list, you can make it available at any URI. Prefer pinning your list to IPFS (e.g. via pinata.cloud) but you can also upload to Github. If you'd like to add a new list to Pegasys, you can submit a PR here.
If hosted on HTTPS, make sure the endpoint is configured to send an access-control-allow-origin header to avoid CORS errors.
You can find a simple example of a token list in test/schema/example.tokenlist.json.
Below is a list of commands you will probably find useful.
yarn start
Runs the project in development/watch mode. Your project will be rebuilt upon changes. TSDX has a special logger for you convenience. Error messages are pretty printed and formatted for compatibility VS Code's Problems tab.
Your library will be rebuilt if you make edits.
yarn build
Bundles the package to the dist folder.
The package is optimized and bundled with Rollup into multiple formats (CommonJS, UMD, and ES Module).
yarn test
Runs the test watcher (Jest) in an interactive mode. By default, runs tests related to files changed since the last commit.
This code was adapted from this Uniswap repo: token-lists.