Lightning Web Components – Workaround for LWR3008 Error (404 Status) in LWR Site

Ok, so there's something funky going on with the Flow engine, and the formula approach is a bit of a red herring.

Short answer, I don't think there's anything wrong with {!$GlobalConstant.True}.

The issue is with the default value.

In my meta.xml, I had default="true" for inputBoolean, so when I added the component to the flow screen, I didn't need to set the value of inputBoolean because it was already set.

If I clear {!$GlobalConstant.True} out of inputBoolean, then add it in again, the component behaves as expected.

This would be why the formula worked; because it wasn't using the default value.

If you come across this issue, just clear the default value out of the input, and add it back again.

I've see this happen with text inputs as well.

It seems you know the way to actually do this - setting the variables as input/output and passing it in and storing output in the Flow setup. Considering the LWC is re-initialized when going back to the screen (or in the case of validation error) - it needs values passed in for your situation.

So if you don't want to use the mechanism provided with Flow/LWC, you'd have to leverage another mechanism - something like browser sessionStorage to store/retrieve values.

export default class GroceryPicker extends LightningElement {
    @api category;
    @api item;

    //set existing selected value by user 
    connectedCallback(){
        this.categoryOptions = //set category options 
        //check if there's a cached selection by this user
        let cachedSelection= sessionStorage.getItem(this.sessionStorageKey);
        if(cachedSelection && this.validateSessionStorageValue(cachedSelection){
            this.category = cachedSelection;
        }
    }

    handleCategoryChange(event) {
        this.category = event.target.value;
        //set the value in session storage to retrieve, if needed, later
        sessionStorage.setItem(this.sessionStorageKey, event.target.value);
    }

    get sessionStorageKey() {
        //create some sort of unique key - add any relevant variables for flow (recordId) to make it unique per user (can pull userId)
        return 'groceryPickerCategory.${this.userId}';
        
    }
    
    validateSessionStorageValue(retrievedValue) {
        this.categoryOptions.forEach(option => {
            if(option.value === retrievedValue){
                return true;
            }
        }
        return false;
    }
}

Considerations

• Only showed an example for categories based on your question
• You'll probably want to validate the value you pull from session storage against your list of valid values
• If the user quits the flow screen - the value is saved. That may or may not be desirable behavior to have it autofill if they click it again.