feat: add accountAdded and accountRemoved events (#4496)

## Explanation

This PR adds the following events to the `AccountsController`,
`accountAdded` and `accountRemoved`.

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### `@metamask/accounts-controller`

- **ADDED**: Adds `accountAdded` and `accountRemoved` events. 

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've highlighted breaking changes using the "BREAKING" category
above as appropriate

---------

Co-authored-by: Charly Chevalier <charly.chevalier@consensys.net>

packages/accounts-controller/src/AccountsController.test.ts

@@ -919,6 +919,50 @@ describe('AccountsController', () => {
         ]);
         expect(accountsController.getSelectedAccount().id).toBe(mockAccount.id);
       });
+
+      it('publishes accountAdded event', async () => {
+        const messenger = buildMessenger();
+        const messengerSpy = jest.spyOn(messenger, 'publish');
+        mockUUID
+          .mockReturnValueOnce(mockAccount.id) // call to check if its a new account
+          .mockReturnValueOnce(mockAccount2.id) // call to check if its a new account
+          .mockReturnValueOnce(mockAccount2.id); // call to add account
+
+        setupAccountsController({
+          initialState: {
+            internalAccounts: {
+              accounts: {
+                [mockAccount.id]: mockAccount,
+              },
+              selectedAccount: mockAccount.id,
+            },
+          },
+          messenger,
+        });
+
+        const mockNewKeyringState = {
+          isUnlocked: true,
+          keyrings: [
+            {
+              type: KeyringTypes.hd,
+              accounts: [mockAccount.address, mockAccount2.address],
+            },
+          ],
+        };
+
+        messenger.publish(
+          'KeyringController:stateChange',
+          mockNewKeyringState,
+          [],
+        );
+
+        // First call is 'KeyringController:stateChange'
+        expect(messengerSpy).toHaveBeenNthCalledWith(
+          2,
+          'AccountsController:accountAdded',
+          setLastSelectedAsAny(mockAccount2),
+        );
+      });
     });
 
     describe('deleting account', () => {
@@ -1155,6 +1199,50 @@ describe('AccountsController', () => {
           currentTime,
         );
       });
+
+      it('publishes accountRemoved event', async () => {
+        const messenger = buildMessenger();
+        const messengerSpy = jest.spyOn(messenger, 'publish');
+        mockUUID
+          .mockReturnValueOnce(mockAccount.id) // call to check if its a new account
+          .mockReturnValueOnce(mockAccount2.id) // call to check if its a new account
+          .mockReturnValueOnce(mockAccount2.id); // call to add account
+
+        setupAccountsController({
+          initialState: {
+            internalAccounts: {
+              accounts: {
+                [mockAccount.id]: mockAccount,
+                [mockAccount3.id]: mockAccount3,
+              },
+              selectedAccount: mockAccount.id,
+            },
+          },
+          messenger,
+        });
+
+        const mockNewKeyringState = {
+          isUnlocked: true,
+          keyrings: [
+            {
+              type: KeyringTypes.hd,
+              accounts: [mockAccount.address, mockAccount2.address],
+            },
+          ],
+        };
+        messenger.publish(
+          'KeyringController:stateChange',
+          mockNewKeyringState,
+          [],
+        );
+
+        // First call is 'KeyringController:stateChange'
+        expect(messengerSpy).toHaveBeenNthCalledWith(
+          2,
+          'AccountsController:accountRemoved',
+          mockAccount3.id,
+        );
+      });
     });
 
     it('handle keyring reinitialization', async () => {

packages/accounts-controller/src/AccountsController.ts

@@ -42,9 +42,11 @@ import {
 
 const controllerName = 'AccountsController';
 
+export type AccountId = string;
+
 export type AccountsControllerState = {
   internalAccounts: {
-    accounts: Record<string, InternalAccount>;
+    accounts: Record<AccountId, InternalAccount>;
     selectedAccount: string; // id of the selected account
   };
 };
@@ -137,12 +139,24 @@ export type AccountsControllerSelectedEvmAccountChangeEvent = {
   payload: [InternalAccount];
 };
 
+export type AccountsControllerAccountAddedEvent = {
+  type: `${typeof controllerName}:accountAdded`;
+  payload: [InternalAccount];
+};
+
+export type AccountsControllerAccountRemovedEvent = {
+  type: `${typeof controllerName}:accountRemoved`;
+  payload: [AccountId];
+};
+
 export type AllowedEvents = SnapStateChange | KeyringControllerStateChangeEvent;
 
 export type AccountsControllerEvents =
   | AccountsControllerChangeEvent
   | AccountsControllerSelectedAccountChangeEvent
-  | AccountsControllerSelectedEvmAccountChangeEvent;
+  | AccountsControllerSelectedEvmAccountChangeEvent
+  | AccountsControllerAccountAddedEvent
+  | AccountsControllerAccountRemovedEvent;
 
 export type AccountsControllerMessenger = RestrictedControllerMessenger<
   typeof controllerName,
@@ -951,7 +965,7 @@ export class AccountsController extends BaseController<
       Object.values(accountsState),
     );
 
-    accountsState[newAccount.id] = {
+    const newAccountWithUpdatedMetadata = {
       ...newAccount,
       metadata: {
         ...newAccount.metadata,
@@ -960,6 +974,12 @@ export class AccountsController extends BaseController<
         lastSelected: isFirstAccount ? this.#getLastSelectedIndex() : 0,
       },
     };
+    accountsState[newAccount.id] = newAccountWithUpdatedMetadata;
+
+    this.messagingSystem.publish(
+      'AccountsController:accountAdded',
+      newAccountWithUpdatedMetadata,
+    );
 
     return accountsState;
   }
@@ -988,6 +1008,12 @@ export class AccountsController extends BaseController<
     accountId: string,
   ): AccountsControllerState['internalAccounts']['accounts'] {
     delete accountsState[accountId];
+
+    this.messagingSystem.publish(
+      'AccountsController:accountRemoved',
+      accountId,
+    );
+
     return accountsState;
   }
 

packages/accounts-controller/src/index.ts

@@ -12,6 +12,8 @@ export type {
   AccountsControllerChangeEvent,
   AccountsControllerSelectedAccountChangeEvent,
   AccountsControllerSelectedEvmAccountChangeEvent,
+  AccountsControllerAccountAddedEvent,
+  AccountsControllerAccountRemovedEvent,
   AccountsControllerEvents,
   AccountsControllerMessenger,
 } from './AccountsController';