Show an error message in an LWC in a Flow using standard components

Question

I have a custom Lightning Web Component that I am using in a Flow. Unfortunately, the standard ShowToastEvent event does not work when an LWC is in a Flow.

Is there an alternative component I can use for this? Not necessarily a toast message, but something I can use without creating a separate component.

Something like on the standard detail page perhaps?

This is my component, and I want to handle any errors from the delete button.

<template>
    <lightning-record-form
        record-id={recordId}
        object-api-name={objectApiName}
        layout-type="Full"
        mode="view"
    ></lightning-record-form>
    <template if:true={showDeleteButton}>
        <lightning-button variant="destructive" label="Delete" icon-name="utility:delete" onclick={handleDelete}></lightning-button>
    </template>
</template>

Answer 1

Other than using a customization such as unofficialsf.com's Show Toast Flow Action, I don't know of any standard way to address this issue. There are, however, many ways you could deal with errors, inline within your own LWC components.

An example might be to use something like this in your component, showing this part of the template when there's an error (which would typically actually originate from a property of your LWC):

<div class="slds-theme_error">
    <lightning-icon icon-name="utility:error" variant="inverse" size="small"></lightning-icon>
    <span class="slds-p-left_xx-small">Some error message</span>
</div>

This might look something like:

Alternatively, you might like to use the lightning-alert component to present the message in a dismissable "dialog".

There are many other options you could choose from, including simply showing the errors in toasts (though as you said these may not work in all contexts).