feat(account-api): add reverse mapping + AccountProvider events

[ccharly]

Implement reverse-mapping + event mechanism for the AccountProvider.

This also solve the issue that a wallet might not know when a new multichain account got added to the wallet.

For now, we omitted any use of :accountRemoved event since we don't plan to remove those accounts for the moment.

[ccharly]

Required for the Messenger, but we will change that to @metamask/messenger once available.

[cursor]

Bug: Account Retrieval Method Returns Incorrect Type

The abstract method AccountProvider.getAccount is incorrectly typed to return Bip44Account<Account>. It should return Bip44Account<Account> | undefined. This forces implementations to either throw an error or use unsafe type casting (as seen in MockAccountProvider) when an account with the given ID is not found. This can lead to runtime crashes in MultichainAccount.getAccount and MultichainAccount.getAccounts if their internal account ID lists become out of sync with the provider's actual state, causing them to request non-existent accounts from the provider.

packages/account-api/src/api/provider.ts#L34-L35

accounts/packages/account-api/src/api/provider.ts

Lines 34 to 35 in d968dd7

	*/
	abstract getAccount(id: Bip44Account<Account>['id']): Bip44Account<Account>;

packages/account-api/src/api/multichain/account.ts#L120-L128

accounts/packages/account-api/src/api/multichain/account.ts

Lines 120 to 128 in d968dd7

	allAccounts = allAccounts.concat(
	accounts
	.map((id) => provider.getAccount(id))
	.filter(
	(account) =>
	account.options.entropy.id === this.wallet.entropySource &&
	account.options.entropy.groupIndex === this.index,
	),
	);

packages/account-api/src/api/multichain/account.ts#L146-L149

accounts/packages/account-api/src/api/multichain/account.ts

Lines 146 to 149 in d968dd7

	return undefined;
	}
	return provider.getAccount(id);
	}

packages/account-api/src/index.test.ts#L159-L167

accounts/packages/account-api/src/index.test.ts

Lines 159 to 167 in d968dd7

	getAccount = jest
	.fn()
	.mockImplementation((id: InternalAccount['id']): InternalAccount => {
	// Assuming this never fails.
	return this.#accounts.find(
	(account) => account.id === id,
	) as InternalAccount;
	});

Fix in Cursor • Fix in Web

---

Bug: Multichain Account Retrieval Returns Incorrect Accounts

The MultichainAccount.getAccount() method can return accounts that do not belong to the specific multichain account. This is due to the reverse map, used by getAccount(), being populated in the constructor with all accounts from providers, instead of only those matching the multichain account's entropy.id and entropy.groupIndex. Consequently, getAccount() retrieves accounts based solely on ID presence in this unfiltered map, without validating their entropy properties, a check correctly performed by getAccounts().

packages/account-api/src/api/multichain/account.ts#L139-L149

accounts/packages/account-api/src/api/multichain/account.ts

Lines 139 to 149 in d968dd7

	*/
	getAccount(id: Account['id']): Bip44Account<Account> | undefined {
	const provider = this.#reverse.get(id);
	// If there's nothing in the map, it means we tried to get an account
	// that does not belong to this multichain account.
	if (!provider) {
	return undefined;
	}
	return provider.getAccount(id);
	}

packages/account-api/src/api/multichain/account.ts#L57-L72

accounts/packages/account-api/src/api/multichain/account.ts

Lines 57 to 72 in d968dd7

	for (const provider of providers) {
	// We only use IDs to always fetch the latest version of accounts.
	const accounts = provider.getAccounts().map((account) => account.id);
	this.#accounts.push({
	provider,
	accounts,
	});
	// Reverse-mapping for fast indexing.
	for (const id of accounts) {
	this.#reverse.set(id, provider);
	}
	}
	}

Fix in Cursor • Fix in Web

---

Was this report helpful? Give feedback by reacting with 👍 or 👎