eth-saddle

Saddle

Saddle is a simple framework for developing Ethereum Smart Contracts. Think of it like a lean and mean version of truffle.

Philosophy

What saddle does

• Allows you to compile and deploy your contracts.
• Add fast, parallelized tests for your contracts.
• Trace and debug your contracts
• Verify your contracts on Etherscan

What saddle does not

• Migrations. It's just "deploy".
• Solidity-language tests
• npm-based Solidity plugins
• solcjs [that is, for performance, saddle requires native solc]

Installing Saddle

To install saddle, simply create a new npm or yarn project and run:

yarn add eth-saddle
# or
npm install eth-saddle --save

Using Saddle

After you've installed saddle, you can compile, test or deploy your contracts. See saddle help for more information. See configuration below for configuration help.

Let's assume you define a simple Ethereum contract:

contracts/MyContract.sol

pragma solidity ^0.5.12;

contract MyContract {
	function myFunc() pure external returns (uint256) {
		return 55;
	}
}

Now, you can compile your contract with:

npx saddle compile

saddle compile will compile your contracts and store the built output in ./build/contracts.json. This is the raw output of solc compile.

After you've compiled, you can deploy your contracts:

npx saddle deploy -n development

This will deploy your comiled contracts to development (for this, you should have ganache-cli running). For more information on configuring your deployment for rinkeby or mainnet, see the configuration section below.

After you have deployed, you will also see the contract address listed in ./build/development.json, if you want to keep track of your deployments.

Testing Smart Contracts

Note: before testing, you currently have to compile your contracts. To run your tests, then, run:

npx saddle compile && npx saddle test

saddle test runs your tests. To add tests, create a directory /tests and add some simple tests, e.g.

tests/MyTest.js

describe('View', () => {
  test('deploy and read contract', async () => {
    let ctx = await deploy('MyContract', []);

    expect(await call(ctx.methods.myFunc())).toEqual(55);
  });
}

Saddle provides a few helper functions for your tests, which are:

• web3 - A web3 instance connected to the chosen provider
• account - The default account for web3
• accounts - A list of unlocked accounts for web3
• deploy(contract: string, args: any[], sendOptions: SendOptions={}) - Deploys a contract
• call(contract: Contract, method: string, arguments: any[], callOptions: CallOptions={}) - Call a function on a contract
• send(contract: Contract, method: string, arguments: any[], sendOptions: SendOptions={}) - Send a transaction on a contract

You can really get by without using most of these functions (except maybe deploy), since they are light wrappers around web3 functions, but the wrappers will allow saddle to provide better helpers and diagnostics in the future.

Tracing

Saddle comes with a tracing library that can analyze transaction receipts. This is useful in debugging and testing. For example:

test('balance has one read', async () => {
  // Run the transaction (here, balanceOf) so we can trace it
  let trxReceipt = await comp.methods.balanceOf(saddle.accounts[0]).send();

  await saddle.trace(trxReceipt, {
    constants: {
      "account": saddle.accounts[0] // tracing code will note this as an address
    },
    preFilter: ({op}) => op === 'SLOAD', // filter all operations to find only SLOADs
    // we can filter by source code if we want
    // note: source code only available when running in `trace mode`
    postFilter: ({source}) => !source || source.includes('balanceOf'),
    execLog: (log) => {
      log.show(); // show each load operation
    },
    exec: (logs, info) => {
      expect(logs.length).toEqual(1); // make sure there's only one matching operation
    }
  });
});

The code above will trace and make sure only one Ethereum read operation was called in that operation. The logs (when run in trace mode) will look like this:

Log       pc=503 op=SLOAD source=contracts/Token.sol:100[24-45]
Solidity  uint balance = _balances[account];
          ↓
EVM Asm   SLOAD[SHA3(CONCAT(account,0x4))]-> 0x1

That is, when the program counter (PC) reached 503, we did an SLOAD from line 100 of Token.sol (shown below). The SLOAD was based on the SHA3 of the account address added to 0x4 (Solidity's fourth slot) and yielded a balance of 1 wei.

Trace Features:

• constants - Saddle's data analysis tool will note that these values should be tokenized. Note: saddle expects values like this to be globally unique (like addresses or hash results).
• preFilter - Given a simple trace log object, return true to continue processing on that log. Each log will go through detailed tracing and it's good to remove irrelevant logs here.
• postFilter - After each log has been analyzed and mapped to source code, you can add additional filters here.
• execLog - Once per log, run the following (possibly async) function.
• exec - Once per trace, run the following function with all logs passed in.

If you have new features or analysis you'd like to add to tracing, feel free to open an issue or craft a PR. The goal is to make useful analysis tools to help bridge the mental model of Solidity to the Ethereum virtual machine.

CLI

Deploying a contract:

npx saddle deploy MyContract Arg0 Arg1 -n rinkeby

Verifying a contract on Etherscan:

npx saddle verify "{Etherscan API Key}" MyContract Arg0 Arg1 -n rinkeby

Configuration

Saddle comes with reasonable default configuration, but you can override it. The core of the configuration is a list of "sources" for any given configuration-item, allowing the framework to look at say an environment variable for a provider, or if that is missing, a file with the provider information, or if that is missing, use a default http endpoint. This would be described as:

...
provider: [{env: "PROVIDER"}, {file: "~/.ethereum-provider"}, {http: "http://rinkeby.infura.io"}]

To set your own configuration, simply run: saddle init and this will create a file saddle.config.js. Make any changes to the configuration you need in that file

Contributing

Please create an issue for any questions. In the interest of keeping saddle as simple as possible, we will not try to mimic all features of more complex frameworks-- so it's better to discuss first before submitting PRs.

Thanks and enjoy!