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@truffle/abi-utils

Contains a few utilities for dealing with ABIs.

Contents

This package contains a few different components:

• Normalize ABIs
• TypeScript types
• Selector and signature computation
• Signature parsing
• Arbitrary random ABIs

Normalize ABIs

// handle function entries omitting "type" from JSON
const isFunctionEntry = entry.type === "function" || !("type" in entry);

// handle:        v--- new way                           v--- old way     v--- default
const isPayable =
  entry.stateMutability === "payable" || entry.payable || false;

// handle "outputs" possibly being undefined
const outputs = entry.outputs || [];

^ Have you ever had to do this sort of thing? 😱

Solidity's official JSON ABI specification is rather permissive, since it remains backwards compatible with older versions of the language and because it permits omitting fields with default values. This can get annoying if you're programmatically processing ABIs.

ℹ️ This package provides a normalize function to purge these kinds of inconsistencies.

const { normalize } = require("@truffle/abi-utils");

import { normalize } from "@truffle/abi-utils";

Specifically, this normalizes by:

• Ensuring every ABI entry has a type field, since it's optional for type: "function"
• Populating default value [] for function outputs field
• Removing all instances of the legacy payable and constant fields
• Replacing those two fields with the newer stateMutability field

To use, provide the ABI as a JavaScript array, as the sole argument to the function:

// accepts ABIs from Solidity versions back to 0.4.12 or earlier!
const abi = normalize([{"type": "constructor"/*, ...*/}/*, ...*/);

// don't even worry about it
const isFunctionEntry = entry.type === "function";
const isPayable = entry.stateMutability === "payable";

TypeScript types

This package exports the following types for normalized ABIs.

• Abi, to represent the full ABI array
• Entry, to represent items in ABI arrays
• FunctionEntry, to represent named functions
• ConstructorEntry, to represent constructors
• FallbackEntry, to represent old or new fallback functions
• ReceiveEntry, to represent receive functions
• Parameter, to represent parameters defined in entry inputs or outputs
• EventParameter, to represent event parameters

To use these, you should first call normalize, described above.

import * as Abi from "@truffle/abi-utils";

const abi: Abi.Abi = [{ type: "constructor" /*, ...*/ } /*, ...*/];
const parameter: Abi.Parameter = {
  type: "tuple[]",
  components: [
    /*...*/
  ]
};
// etc.

Selector and signature computation

This package exports the following functions for computing signatures and selectors:

• abiSelector: This function takes a FunctionEntry, EventEntry, or ErrorEntry and computes its selector, returned as a hex string. This will be 4 bytes for a function or error, and 32 bytes for an event.
• abiSignature: This function takes a FunctionEntry, EventEntry, or ErrorEntry and computes its written-out signature (e.g., "setStoredValue(uint256)").
• abiTupleSignature: This function takes a Parameter[] and computes the signature of that tuple on its own; e.g., "(uint256,string)" for a uint and a string.
• abiTypeSignature: This function takes an individual Parameter and computes the signature of that type on its own; e.g., uint256 for a uint.

In addition, the package also exports the constant ShortSelectorSize, which is equal to 4 (the number of bytes in a function or event selector).

Signature parsing

This package exports several functions for parsing signatures back to full ABI entries. Note that because signatures lose a lot of information, much of the result will be filled with default vales; functions will always be marked as having no outputs and as being nonpayable, events will always be marked as non-anonymous and their parameters marked as non-indexed.

You can parse signatures with the parseFunctionSignature, parseEventSignature, and parseErrorSignature functions, depending on what type of ABI entry you want.

There's also parseSignature, which will not produce a valid ABI entry, but will produce an object with name and inputs. The inputs will not have indexed fields. And there's also parseParameterList, which can be used on a signature with the name removed to get just the inputs.

Note that these functions do not currently perform full validation of all the types used in the signature, so if you include invalid types in your signature, the parser may reproduce these in the output ABI. Stricter validation may be added at a later date.

Arbitrary random ABIs

Do you need to test all the different kinds of ABIs, including testing your support for the various quirks across different Solidity versions? 😳

You can use this package for generating all sorts of random ABIs, random ABI events, random ABI parameter values, etc.

This package provides fast-check arbitraries for property-based testing methodologies. If you're not familiar with fast-check or property-based testing, please see the link above for more information.

import * as fc from "fast-check";
import { Arbitrary } from "@truffle/abi-utils";

// generate 10 random ABIs
const randomAbis = fc.sample(Arbitrary.Abi(), 10);

See this package's internal tests for normalize for example usage in automated tests.