public async loadMoreChildrenImpl()

in ui/src/tree/AzureAccountTreeItemBase.ts [69:148]
70 lines of code
11 McCabe index (conditional complexity)

    public async loadMoreChildrenImpl(_clearCache: boolean, context: types.IActionContext): Promise<AzExtTreeItem[]> {
        let azureAccount: AzureAccountResult = await this._azureAccountTask;
        if (typeof azureAccount === 'string') {
            // Refresh the AzureAccount, to handle Azure account extension installation after the previous refresh
            this._azureAccountTask = this.loadAzureAccount(this._testAccount);
            azureAccount = await this._azureAccountTask;
        }

        if (typeof azureAccount === 'string') {
            context.telemetry.properties.accountStatus = azureAccount;
            const label: string = azureAccount === 'notInstalled' ?
                localize('installAzureAccount', 'Install Azure Account Extension...') :
                localize('updateAzureAccount', 'Update Azure Account Extension to at least version "{0}"...', minAccountExtensionVersion);
            const iconPath: types.TreeItemIconPath = new ThemeIcon('warning');
            const result: AzExtTreeItem = new GenericTreeItem(this, { label, commandId: extensionOpenCommand, contextValue: 'azureAccount' + azureAccount, includeInTreeItemPicker: true, iconPath });
            result.commandArgs = [azureAccountExtensionId];
            return [result];
        }

        context.telemetry.properties.accountStatus = azureAccount.status;
        const existingSubscriptions: SubscriptionTreeItemBase[] = this._subscriptionTreeItems ? this._subscriptionTreeItems : [];
        this._subscriptionTreeItems = [];

        const contextValue: string = 'azureCommand';
        if (azureAccount.status === 'Initializing' || azureAccount.status === 'LoggingIn') {
            return [new GenericTreeItem(this, {
                label: azureAccount.status === 'Initializing' ? localize('loadingTreeItem', 'Loading...') : localize('signingIn', 'Waiting for Azure sign-in...'),
                commandId: signInCommandId,
                contextValue,
                id: signInCommandId,
                iconPath: new ThemeIcon('loading~spin')
            })];
        } else if (azureAccount.status === 'LoggedOut') {
            return [
                new GenericTreeItem(this, { label: signInLabel, commandId: signInCommandId, contextValue, id: signInCommandId, iconPath: new ThemeIcon('sign-in'), includeInTreeItemPicker: true }),
                new GenericTreeItem(this, { label: createAccountLabel, commandId: createAccountCommandId, contextValue, id: createAccountCommandId, iconPath: new ThemeIcon('add'), includeInTreeItemPicker: true })
            ];
        }

        await azureAccount.waitForFilters();

        if (azureAccount.filters.length === 0) {
            return [
                new GenericTreeItem(this, { label: selectSubscriptionsLabel, commandId: selectSubscriptionsCommandId, contextValue, id: selectSubscriptionsCommandId, includeInTreeItemPicker: true })
            ];
        } else {
            this._subscriptionTreeItems = await Promise.all(azureAccount.filters.map(async (filter: AzureResourceFilter) => {
                const existingTreeItem: SubscriptionTreeItemBase | undefined = existingSubscriptions.find(ti => ti.id === filter.subscription.id);
                if (existingTreeItem) {
                    // Return existing treeItem (which might have many 'cached' tree items underneath it) rather than creating a brand new tree item every time
                    return existingTreeItem;
                } else {
                    addExtensionValueToMask(
                        filter.subscription.id,
                        filter.subscription.subscriptionId,
                        filter.subscription.displayName,
                        filter.session.userId,
                        filter.session.tenantId,
                        filter.session.credentials2.clientId,
                        filter.session.credentials2.domain
                    );

                    // filter.subscription.id is the The fully qualified ID of the subscription (For example, /subscriptions/00000000-0000-0000-0000-000000000000) and should be used as the tree item's id for the purposes of OpenInPortal
                    // filter.subscription.subscriptionId is just the guid and is used in all other cases when creating clients for managing Azure resources
                    const subscriptionId: string = nonNullProp(filter.subscription, 'subscriptionId');
                    return await this.createSubscriptionTreeItem({
                        credentials: filter.session.credentials2,
                        subscriptionDisplayName: nonNullProp(filter.subscription, 'displayName'),
                        subscriptionId,
                        subscriptionPath: nonNullProp(filter.subscription, 'id'),
                        tenantId: filter.session.tenantId,
                        userId: filter.session.userId,
                        environment: filter.session.environment,
                        isCustomCloud: filter.session.environment.name === 'AzureCustomCloud'
                    });
                }
            }));
            return this._subscriptionTreeItems;
        }
    }