How to migrate existing Aragon App to Buidler plugin

This guide aims to describe the basic steps needed to migrate an existing Aragon App from the aragonCLI to the new Buidler plugin. This new Aragon tool offers a more user-friendly and stable developer experience. You can learn more about the Buidler plugin here.
For this tutorial, we will assume that you have existing Aragon App which was setup with aragonCLI and now needs migration to the new Builder plugin.
1. Install dependencies
The first step is to install the following NPM development dependencies:
"@aragon/buidler-aragon": "^0.1.0"
"@aragon/contract-test-helpers": "0.0.1"
"@nomiclabs/buidler": "^1.0.2"
"@nomiclabs/buidler-truffle5": "^1.1.2"
"@nomiclabs/buidler-web3": "^1.1.2"
"bignumber.js": "^9.0.0"
"web3": "^1.2.6"
The command for installing the dependencies is:
yarn add <dependencies>
Most of these dependencies should be new to your project and are related to Nomic Labs' Buidler (now Hardhat), a task runner for Ethereum smart contract developers. However, one dependency that you may need to upgrade is web3, since Aragon's plugin requires v1.2.6 or higher. This may introduce some breaking changes, mostly in tests. See the Migrate tests section for more information.
2. Add/replace npm scripts
Since the app won't use aragonCLI anymore, some NPM scripts need to be changed.
In package.json:
"postinstall": "yarn compile && yarn build-app"
"build-app": "cd app && npm install && cd .."
"compile": "buidler compile --force"
"start": "buidler start"
"test": "buidler test --network buidlerevm"
Also, make sure that you have the following two scripts in app/package.json (note that this is a different package.json than you just edited!):
serve: Launches the webserver (Previously called devserver script in most projects)
watch: Watches for file changes (Previously called watch:script script in most projects)
3. Update .gitignore file
Add the following two folders to your .gitignore file:
artifacts
cache
4. Create the Buidler config file
Add the following buidler.config.js file to the root of your project:
const { usePlugin } = require('@nomiclabs/buidler/config')
​
usePlugin('@aragon/buidler-aragon')
​
module.exports = {
  defaultNetwork: 'localhost',
  networks: {
    localhost: {
      url: 'http://localhost:8545',
    },
  },
  solc: {
    version: '0.4.24',
    optimizer: {
      enabled: true,
      runs: 10000,
    },
  },
  aragon: {
    appServePort: 1234,
    clientServePort: 3000,
    appSrcPath: 'app/',
    appBuildOutputPath: 'dist/',
    hooks: require('./scripts/buidler-hooks'),
  },
}
You can find more information about the Buidler configuration file here (now Hardhat). As for the aragon section, it contains 5 main options:
appServePort: The app server port started by the serve script of the app folder. (Default: 1234)
clientServePort: Aragon client server port.
appSrcPath: Frontend source for the app.
appBuildOutputPath: Built app path.
hooks: Aragon hooks functions. (See Hooks section for more information)
5. Hooks
Hooks are custom functions called at various stages of an app initialization. They can be used to execute any logic before or after the app is created and also to specify the app's initialize() function parameters. For example, initializing the app with a uint256 and a string would be as simple as writing the following hook:
getInitParams: async ({}, { web3, artifacts }) => {
  return [23, 'Hello, World!']
}
If you were using a template contract before to initialize organization state during aragon run, you should convert the smart contract logic into the hooks. Because hooks are much easier to write, maintain, and debug, the Buidler plugin will not be supporting template contracts. You can find complete examples in 1Hive's Conviction Voting and Payroll apps. In our case, we will simply add empty functions since we don't need any initialization logic. So we will create a file named buidler-hooks.js in the scripts folder and add the following code:
module.exports = {
  // Called before a dao is deployed.
  preDao: async ({}, { web3, artifacts }) => {},
​
  // Called after a dao is deployed.
  postDao: async ({ dao }, { web3, artifacts }) => {},
​
  // Called after the app's proxy is created, but before it's initialized.
  preInit: async ({ proxy }, { web3, artifacts }) => {},
​
  // Called after the app's proxy is initialized.
  postInit: async ({ proxy }, { web3, artifacts }) => {},
​
  // Called when the start task needs to know the app proxy's init parameters.
  // Must return an array with the proxy's init parameters.
  getInitParams: async ({}, { web3, artifacts }) => {
    return []
  },
​
  // Called after the app's proxy is updated with a new implementation.
  postUpdate: async ({ proxy }, { web3, artifacts }) => {},
}
5. Migrate tests
Since the Aragon Buidler plugin uses truffle 5, you may have to migrate part of your tests. You can follow this guide or the truffle team announcement.
Nevertheless, the following tips can be helpful:
Async/Await
Most truffle contract functions are now asynchronous, so code like this:
const dao = Kernel.at('0x9d1C272D0541345144D943470B3a90f14c56910c')
should become:
const dao = await Kernel.at('0x9d1C272D0541345144D943470B3a90f14c56910c')
Web3.js 1.2
Truffle 5 is using Web3.js 1.2 instead of 0.20, which comes with a few changes:
​PromiEvent objects.
Addresses are now mixed-case instead of lower-case.
Many Web3 utility functions have been moved to web3.utils​
Numbers returned directly from Web3 are now strings.
Functions that return multiple values now return an object with both named and indexed keys.
BN.js
Truffle 5 has also replaced bignumber.js with BN.js. Instances of web3.BigNumber() will therefore have to be changed to web3.utils.toBN().
Ethereum addresses
You now need to use full Ethereum addresses instead of partial ones like 0x0. So this address:
const ZERO = '0x00'
would become:
const ZERO = '0x0000000000000000000000000000000000000000'
Coverage
A useful Buidler plugin is available here for Solidity code coverage.
6. Start the app and uninstall unnecessary dependencies
You are now ready to start your app:
yarn start
You can also uninstall dependencies that are no longer required:
@aragon/cli
ganache-cli
truffle
yarn remove <dependencies>
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Last modified 4mo ago