How do derive a keypair from mnemonic using web3.js v2?

Question

I don't see an equivalent of Keypair.fromSeed() in keypair-signer.d.ts

How do you derive a keypair from mnemonic using web3.js v2?

import { Address } from '@solana/addresses';
import { ReadonlyUint8Array } from '@solana/codecs-core';
import { MessagePartialSigner } from './message-partial-signer';
import { TransactionPartialSigner } from './transaction-partial-signer';
/** Defines a signer capable of signing messages and transactions using a CryptoKeyPair. */
export type KeyPairSigner<TAddress extends string = string> = MessagePartialSigner<TAddress> & TransactionPartialSigner<TAddress> & {
    keyPair: CryptoKeyPair;
};
/** Checks whether the provided value implements the {@link KeyPairSigner} interface. */
export declare function isKeyPairSigner<TAddress extends string>(value: {
    [key: string]: unknown;
    address: Address<TAddress>;
}): value is KeyPairSigner<TAddress>;
/** Asserts that the provided value implements the {@link KeyPairSigner} interface. */
export declare function assertIsKeyPairSigner<TAddress extends string>(value: {
    [key: string]: unknown;
    address: Address<TAddress>;
}): asserts value is KeyPairSigner<TAddress>;
/** Creates a KeyPairSigner from the provided Crypto KeyPair. */
export declare function createSignerFromKeyPair(keyPair: CryptoKeyPair): Promise<KeyPairSigner>;
/** Securely generates a signer capable of signing messages and transactions using a Crypto KeyPair. */
export declare function generateKeyPairSigner(): Promise<KeyPairSigner>;
/** Creates a signer capable of signing messages and transactions using the 64 bytes of a KeyPair. */
export declare function createKeyPairSignerFromBytes(bytes: ReadonlyUint8Array, extractable?: boolean): Promise<KeyPairSigner>;
/** Creates a signer capable of signing messages and transactions using the 32 bytes of a private key. */
export declare function createKeyPairSignerFromPrivateKeyBytes(bytes: ReadonlyUint8Array, extractable?: boolean): Promise<KeyPairSigner>;
//# sourceMappingURL=keypair-signer.d.ts.map

Answer 1

In @solana/web3.js version 1, Keypair.fromSeed(seed) simply uses the provided seed as the private key of the key pair.

The equivalent in @solana/web3.js version 2 is createKeyPairFromPrivateKeyBytes (See documentation).

const keypair = await createKeyPairFromPrivateKeyBytes(seed);

If you want a signer from this key pair directly, you may use the following helper instead (See documentation).

const signer = await createKeyPairSignerFromPrivateKeyBytes(seed);