SFSE #255489

comparisonTable.html

<template>
    <lightning-card title="Products" icon-name="custom:custom63">
        <div class="slds-m-around_medium">
            <template if:true={error}>
                <p>{error}</p>
                <p>{error.message}</p>
            </template>
            <template if:true={products}>
                <lightning-datatable
                    key-field="Id"
                    data={products}
                    columns={columns}
                    is-loading={tableIsLoading}
                    hide-checkbox-column="true"
                ></lightning-datatable>
            </template>
        </div>
    </lightning-card>
</template>

comparisonTable.js

import { LightningElement, track, api } from 'lwc'
import getProducts from '@salesforce/apex/ComparisonTableController.getProducts'
import createAccount from '@salesforce/apex/ComparisonTableController.createAccount'

const columns = [
    { label: 'Name', fieldName: 'Product2.Name' },
    { label: 'Base price', fieldName: 'UnitPrice', type: 'currency' },
    { label: 'Product code', fieldName: 'Product2.ProductCode' }
]

export default class ComparisonTable extends LightningElement {
    @track products
    @track columns = columns
    @track tableIsLoading = true
    @track error
    @api pricebookId
    @api recordId

    connectedCallback() {
        getProducts({ pricebookId: this.pricebookId, countLimit: 4 })
            .then(result => {
                this.products = result.map(
                    record => Object.assign(
                        {
                            'Product2.Name': record.Product2.Name,
                            'Product2.ProductCode': record.Product2.ProductCode
                        },
                        record
                    )
                )
                this.tableIsLoading = false
            })
            .catch(error => {
                this.error = error
            })
        createAccount().then(result => {
            console.log('account created')
            console.log(result)
        }).catch(error => {
            console.error('Account creation failed.')
            console.error(JSON.stringify(error))
            this.error = error.body.message
        })
    }
}

ComparisonTableController.cls

public class ComparisonTableController {

    @AuraEnabled(cacheable=true)
    public static List<PricebookEntry> getProducts (Id pricebookId, Integer countLimit) {
        return [
            SELECT
                Id
                ,Product2.Name
                ,Product2.Family
                ,Product2.ProductCode
                ,Product2.IsActive
                ,Product2.QuantityUnitOfMeasure
                ,Product2.StockKeepingUnit
                ,UnitPrice
            FROM PricebookEntry
            WHERE Pricebook2Id = :pricebookId
            LIMIT :countLimit
        ];
    }

    @AuraEnabled
    public static Id createAccount () {
        Account a = new Account();
        try {
            insert a;
        } catch (Exception e) {
            throw new AuraHandledException(e.getMessage());
        }
        return a.Id;
    }
}

The controller class fails when the insert statement is executed by the platform. On the developer console log:

09:01:45:041 FATAL_ERROR System.LimitException: Too many DML statements: 1

The log ends with:

09:01:45:000 LIMIT_USAGE_FOR_NS   Number of DML statements: 1 out of 0 ******* CLOSE TO LIMIT

Which is really weird. I thought that the only thing that prevented a DML operation was marking the method as cacheable, as the documentation says in https://developer.salesforce.com/docs/component-library/documentation/lwc/apex.

So, As I can see, you are queuing 2 Apex Aura Enable call one to fetch getProducts and second to insert record in single apex call. There will be only one debug log saying both are same transaction

@renatoliveira .

According to this, a single governer limit is shared across multiple transactions. https://salesforce.stackexchange.com/a/192881/19118

So in your case when the transaction started the transaction was readOnly and when you do dml in same transaction you get the exception.

Fix would be to split it in 2 transctions, eg by calling createAccount(). in then block of getProducts