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@metamask/abi-utils

Lightweight utilities for encoding and decoding Solidity ABI.

Installation

yarn add @metamask/abi-utils

or

npm install @metamask/abi-utils

Usage

Encoding values

You can encode multiple values using encode.

import { encode } from '@metamask/abi-utils';
import { bytesToHex } from '@metamask/utils';

const encoded = encode(['uint256', 'string'], [42, 'Hello, world!']);

// `abi-utils` returns a `Uint8Array`, so you can convert it to a hex string
// using `bytesToHex`.
console.log(bytesToHex(encoded));

// 0x000000000000000000000000000000000000000000000000000000000000002a
//   0000000000000000000000000000000000000000000000000000000000000040
//   000000000000000000000000000000000000000000000000000000000000000d
//   48656c6c6f2c20776f726c642100000000000000000000000000000000000000

Alternatively, you can encode a single value using encodeSingle.

import { encodeSingle } from '@metamask/abi-utils';

const encoded = encodeSingle('uint256', 42);

// `abi-utils` returns a `Uint8Array`, so you can convert it to a hex string
// using `bytesToHex`.
console.log(bytesToHex(encoded));

// 0x000000000000000000000000000000000000000000000000000000000000002a

Encoding packed values

Encoding packed values, using the non-standard packed mode, is also supported. This behaves the same as abi.encodePacked in Solidity.

import { encodePacked } from '@metamask/abi-utils';

const encoded = encodePacked(['uint256', 'string'], [42, 'Hello, world!']);

// `abi-utils` returns a `Uint8Array`, so you can convert it to a hex string
// using `bytesToHex`.
console.log(bytesToHex(encoded));

// 0x000000000000000000000000000000000000000000000000000000000000002a48656c6c6f2c20776f726c6421

Decoding values

You can decode multiple values using decode.

import { decode } from '@metamask/abi-utils';

const decoded = decode(
  ['uint256', 'string'],
  '0x000000000000000000000000000000000000000000000000000000000000002a' +
    '0000000000000000000000000000000000000000000000000000000000000040' +
    '000000000000000000000000000000000000000000000000000000000000000d' +
    '48656c6c6f2c20776f726c642100000000000000000000000000000000000000',
);

console.log(decoded); // [ 42n, 'Hello, world!' ]

Alternatively, you can decode a single value using decodeSingle.

import { decodeSingle } from '@metamask/abi-utils';

const decoded = decodeSingle(
  'uint256',
  '0x000000000000000000000000000000000000000000000000000000000000002a',
);

console.log(decoded); // 42n

Strict type checking

By default, encode and decode will not perform strict type checking. This is because TypeScript does not narrow the type of the types array being passed to the functions.

If you want to perform strict type checking, you can assert the type of the array as const using the as const assertion.

import { encode } from '@metamask/abi-utils';

// This can be inlined in the function call too.
const types = ['uint256', 'string'] as const;

// Works!
encode(types, [42, 'Hello, world!']);

// Type 'number' is not assignable to type 'string'.
encode(types, [42, 1337]);

This does not support all ABI types, like tuples and nested arrays, because support for recursive types in TypeScript is limited. In those cases, the input or output type will be unknown.

API

The full API documentation for the latest published version of this library is available here.

Contributing

Setup

  • Install Node.js version 16
    • If you are using nvm (recommended) running nvm use will automatically choose the right node version for you.
  • Install Yarn v3
  • Run yarn install to install dependencies and run any required post-install scripts

Testing and Linting

Run yarn test to run the tests once. To run tests on file changes, run yarn test:watch.

Run yarn lint to run the linter, or run yarn lint:fix to run the linter and fix any automatically fixable issues.

Release & Publishing

The project follows the same release process as the other libraries in the MetaMask organization. The GitHub Actions action-create-release-pr and action-publish-release are used to automate the release process; see those repositories for more information about how they work.

  1. Choose a release version.
  • The release version should be chosen according to SemVer. Analyze the changes to see whether they include any breaking changes, new features, or deprecations, then choose the appropriate SemVer version. See the SemVer specification for more information.
  1. If this release is backporting changes onto a previous release, then ensure there is a major version branch for that version (e.g. 1.x for a v1 backport release).
  • The major version branch should be set to the most recent release with that major version. For example, when backporting a v1.0.2 release, you'd want to ensure there was a 1.x branch that was set to the v1.0.1 tag.
  1. Trigger the workflow_dispatch event manually for the Create Release Pull Request action to create the release PR.
  • For a backport release, the base branch should be the major version branch that you ensured existed in step 2. For a normal release, the base branch should be the main branch for that repository (which should be the default value).
  • This should trigger the action-create-release-pr workflow to create the release PR.
  1. Update the changelog to move each change entry into the appropriate change category (See here for the full list of change categories, and the correct ordering), and edit them to be more easily understood by users of the package.
  • Generally any changes that don't affect consumers of the package (e.g. lockfile changes or development environment changes) are omitted. Exceptions may be made for changes that might be of interest despite not having an effect upon the published package (e.g. major test improvements, security improvements, improved documentation, etc.).
  • Try to explain each change in terms that users of the package would understand (e.g. avoid referencing internal variables/concepts).
  • Consolidate related changes into one change entry if it makes it easier to explain.
  • Run yarn auto-changelog validate --rc to check that the changelog is correctly formatted.
  1. Review and QA the release.
  • If changes are made to the base branch, the release branch will need to be updated with these changes and review/QA will need to restart again. As such, it's probably best to avoid merging other PRs into the base branch while review is underway.
  1. Squash & Merge the release.
  • This should trigger the action-publish-release workflow to tag the final release commit and publish the release on GitHub.
  1. Publish the release on npm.
  • Wait for the publish-release GitHub Action workflow to finish. This should trigger a second job (publish-npm), which will wait for a run approval by the npm publishers team.
  • Approve the publish-npm job (or ask somebody on the npm publishers team to approve it for you).
  • Once the publish-npm job has finished, check npm to verify that it has been published.