_section: Migration: From Ethers v4  @<migration-v4>

_subsection: BigNumber

_heading: Namespace
Since [[bignumber]] is used quite frequently, it has been moved to
the top level of the umbrella package.

_code: @lang<script>

// v4
ethers.utils.BigNumber
ethers.utils.BigNumberish

// v5
ethers.BigNumber
ethers.BigNumberish


_heading: Creating Instances
The ``bigNumberify`` method was always preferred over the constructor
since it could short-circuit an object instantiation for [[bignumber]
objects (since they are immutable). This has been moved to a static
``from`` class method.

_code: @lang<script>

// v4
new ethers.utils.BigNumber(someValue)
ethers.utils.bigNumberify(someValue);

// v5
// - Constructor is private
// - Removed `bigNumberify`
ethers.BigNumber.from(someValue)


_subsection: Contracts

_code: @lang<script>

// @TODO


_subsection: Errors

_heading: Namespace
All errors now belong to the [[logger]] class and the related functions
have been moved to [[logger]] instances, which can include a per-package
version string.

Global error fucntions have been moved [[logger]] class methods.

_code: @lang<script>

// v4
ethers.errors.UNKNOWN_ERROR
ethers.errors.*

errors.setCensorship(censorship, permanent)
errors.setLogLevel(logLevel)

errors.checkArgumentCount(count, expectedCount, suffix)
errors.checkNew(self, kind)
errors.checkNormalize()
errors.throwError(message, code, params)
errors.warn(...)
errors.info(...)

// v5
ethers.utils.Logger.errors.UNKNOWN_ERROR
ethers.utils.Logger.errors.*

Logger.setCensorship(censorship, permanent)
Logger.setLogLevel(logLevel)

const logger = new ethers.utils.Logger(version);
logger.checkArgumentCount(count, expectedCount, suffix)
logger.checkNew(self, kind)
logger.checkNormalize()
logger.throwError(message, code, params)
logger.warn(...)
logger.info(...)


_subsection: Interface
The [[abi-interface]] object has undergone the most dramatic changes.

It is no longer a meta-class and now has methods that simplify handling
contract interface operations without the need for object inspection and
special edge cases.

_heading: Functions

_code: @lang<script>

// v4 (example: "transfer(address to, uint amount)")
interface.functions.transfer.encode(to, amount)
interface.functions.transfer.decode(callData)

// v5
interface.encodeData("transfer", [ to, amount ])
interface.decodeResult("transfer", data)

// Or you can use any compatible signature or Fragment objects.
// Notice that signature normalization is performed for you,
// e.g. "uint" and "uint256" will be automatically converted
interface.encodeData("transfer(address,uint)", [ to, amount ])
interface.decodeResult("transfer(address to, uint256 amount)", data)


_heading: Events

_code: @lang<script>

// v4 (example: Transfer(address indexed, address indexed, uint256)
interface.events.Transfer.encodeTopics(values)
interface.events.Transfer.decode(data, topics)

// v5
interface.encodeFilterTopics("Transfer", values)
interface.encodeEventLog("Transfer", data, topics)


_heading: Inspection
Interrogating properties about a function or event can now (mostly) be
done directly on the [[abi-fragment]] object.

_code:

// v4
interface.functions.transfer.name
interface.functions.transfer.inputs
interface.functions.transfer.outputs
interface.functions.transfer.payable
interface.functions.transfer.gas

// v5
const functionFragment = interface.getFunction("transfer")
functionFragment.name
functionFragment.inputs
functionFragment.outputs
functionFragment.payable
functionFragment.gas


// v4; type is "call" or "transaction"
interface.functions.transfer.type

// v5; constant is true (i.e. "call") or false (i.e. "transaction")
functionFragment.constant


// v4
interface.events.Transfer.anonymous
interface.events.Transfer.inputs
interface.events.Transfer.name

// v5
const eventFragment = interface.getEvent("Transfer");
eventFragment.anonymous
eventFragment.inputs
eventFragment.name


// v4
const functionSig = interface.functions.transfer.signature
const sighash = interface.functions.transfer.sighash

const eventSig = interface.events.Transfer.signature
const topic = interface.events.Transfer.topic

// v5
const functionSig = functionFragment.format()
const sighash = interface.getSighash(functionFragment)

const eventSig = eventFragment.format()
const topic = interface.getTopic(eventFragment)


_subsection: Utilities

_heading: Renaming

_code: @lang<script>

// @TODO

_subsection: Wallet

_heading: Mnemonic Phrases
The **mnemonic** phrase and related properties have been merged into
a single ``mnemonic`` object, which also now includes the ``locale``.

_code: @lang<script>

// v4
wallet.mnemonic
wallet.path

// v5
// - Mnemonic phrase and path are a Mnemonic object
// - Note: wallet.mnemonic is null if there is no mnemonic
wallet.mnemonic.phrase
wallet.mnemonic.path