validate post migration state

app/store/index.ts

@@ -14,6 +14,7 @@ import persistConfig from './persistConfig';
 import getUIStartupSpan from '../core/Performance/UIStartup';
 import ReduxService from '../core/redux';
 import { onPersistedDataLoaded } from '../actions/user';
+import { validatePostMigrationState } from './validateState';
 
 // TODO: Improve type safety by using real Action types instead of `any`
 // TODO: Replace "any" with type
@@ -69,6 +70,10 @@ const createStoreAndPersistor = async () => {
     endTrace({ name: TraceName.StoreInit });
     // Signal that persisted data has been loaded
     store.dispatch(onPersistedDataLoaded());
+
+    // validate the state after migration
+    const currentState = store.getState();
+    validatePostMigrationState(currentState);
   };
 
   persistor = persistStore(store, null, onPersistComplete);

app/store/validateState.ts

@@ -0,0 +1,111 @@
+import Logger from '../util/Logger';
+import { RootState } from '../reducers';
+import { AccountsControllerState } from '@metamask/accounts-controller';
+
+/**
+ * Each validation check is a function that:
+ * - Takes the final (post-migration) Redux state,
+ * - Returns an array of error strings if any validations fail or an empty array otherwise.
+ */
+type ValidationCheck = (state: RootState) => string[];
+
+const LOG_TAG = 'MIGRATION_VALIDATE_STATE_ERROR';
+
+/**
+ * Verifies that the engine is initialized
+ */
+const checkEngineInitialized: ValidationCheck = (state) => {
+  const errors: string[] = [];
+  if (!state.engine?.backgroundState) {
+    errors.push(`${LOG_TAG}: Engine backgroundState not found.`);
+  }
+  return errors;
+};
+
+/**
+ * Validates the AccountsControllerState to ensure required
+ * fields exist and match the expected structure.
+ *
+ * @param rootState - The Redux state to validate.
+ * @returns An array of error messages. If empty, the state is valid.
+ */
+const checkAccountsController: ValidationCheck = (rootState) => {
+  const errors: string[] = [];
+
+  // Safely access the AccountsController state in the engine backgroundState
+  const accountsState: AccountsControllerState | undefined =
+    rootState.engine?.backgroundState?.AccountsController;
+
+  // If it's missing altogether, return an error
+  if (!accountsState) {
+    errors.push(
+      `${LOG_TAG}: AccountsController state is missing in engine backgroundState.`,
+    );
+    return errors;
+  }
+
+  // 1. Check that internalAccounts exists
+  if (!accountsState.internalAccounts) {
+    errors.push(
+      `${LOG_TAG}: AccountsController No internalAccounts object found on AccountsControllerState.`,
+    );
+    return errors;
+  }
+
+  const { selectedAccount, accounts } = accountsState.internalAccounts;
+
+  // 2. Confirm there is at least one account
+  if (!accounts || Object.keys(accounts).length === 0) {
+    errors.push(
+      `${LOG_TAG}: AccountsController No accounts found in internalAccounts.accounts.`,
+    );
+    return errors;
+  }
+
+  // 3. Check that selectedAccount is non-empty
+  if (!selectedAccount) {
+    errors.push(
+      `${LOG_TAG}: AccountsController selectedAccount is missing or empty.`,
+    );
+    return errors;
+  }
+
+  // 4. Confirm the selectedAccount ID exists in internalAccounts.accounts
+  if (!accounts[selectedAccount]) {
+    errors.push(
+      `${LOG_TAG}: AccountsController The selectedAccount '${selectedAccount}' does not exist in the accounts record.`,
+    );
+  }
+
+  return errors;
+};
+
+/**
+ * If you have more checks, simply define them above and add them to this array.
+ */
+const checks: ValidationCheck[] = [
+  checkEngineInitialized,
+  checkAccountsController,
+];
+
+/**
+ * Runs all validations and logs any errors, but doesn’t throw.
+ * This makes sure your app keeps running even if some data is unexpected.
+ */
+export function validatePostMigrationState(state: RootState): void {
+  const allErrors: string[] = [];
+
+  for (const check of checks) {
+    const errors = check(state);
+    if (errors.length > 0) {
+      allErrors.push(...errors);
+    }
+  }
+
+  // If there are any errors, log them
+  if (allErrors.length > 0) {
+    Logger.error(new Error('Migration validation errors'), {
+      message: `State validation found these issues: ${allErrors.join(', ')}`,
+    });
+  }
+}