PublishedElementExtensions Value<T> method throws NotImplementedException when using with IPublishedValueFallback

Which Umbraco version are you using? (Please write the exact version, example: 10.1.0)

10.5.1

Bug summary

Hi, there is a strange exception after upgrading from 10.3.2 to 10.5.1.

Quick code review:

We have our BaseView that implements

private SEO? _seo;
public SEO SEO => _seo ??= Model is IPublishedContent content ? new SEO(content, new NoopPublishedValueFallback()) : throw new InvalidOperationException($"{nameof(T)} must implement IPublishedContent");

Which is derrived from SeoComposition, that is generated out of ModelBuilder.

Possible bug

In the interface IPublishedValueFallback there is property IVariationContextAccessor VariationContextAccessor { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } }

This property is used in PublishedElementExtensions method

public static T? Value<T>(
this IPublishedElement content,
IPublishedValueFallback publishedValueFallback,
...

EventuallyUpdateVariationContext(publishedValueFallback, culture, segment);

Since we can’t see if this is anywhere implemented, obviously we get NotImplementedException, which obviously throws this property if called without proper implementation.

I hope you can look into this issue, and that I explained properly what’s the issue, and possible cause of the problem.

Specifics

Possible cause? https://github.com/umbraco/Umbraco-CMS/commit/451d1cec6ab9ea3f1ea269fff3c4e95debfae5e7

Steps to reproduce

Our Issue:

When we call on page SEO.MetaTitle it goes through the code… then we come up to the method in generated composer

/// <summary>Static getter for Meta-Titel</summary>
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Umbraco.ModelsBuilder.Embedded", "10.5.1+c5fe779")]
[return: global::System.Diagnostics.CodeAnalysis.MaybeNull]
public static string GetMetaTitel(ISeoComposition that, IPublishedValueFallback publishedValueFallback) => that.Value<string>(publishedValueFallback, "metaTitel");

Something happens when that.Value<string>(publishedValueFallback, "metaTitel") is called with the publishedValueFallback.

Expected result / actual result

No response

[nikolajlauridsen]

Fixed in #14227

[andr317c]

Hey,

I tried reproducing it and I got the same error. The reason for the error occurring is that you are using the NoopPublishedValueFallback, which doesn’t implement the new members added in https://github.com/umbraco/Umbraco-CMS/commit/451d1cec6ab9ea3f1ea269fff3c4e95debfae5e7. However, NoopPublishedValueFallback is only intended for testing purposes.

A solution could be changing your BaseView to something like this:

public class BaseView<T> : UmbracoViewPage<IPublishedContent>
{
    private SEO? _seo;
    public SEO SEO => _seo ??= Model is IPublishedContent content ? new SEO(content, Context.RequestServices.GetRequiredService<IPublishedValueFallback>()) : throw new InvalidOperationException($"{nameof(T)} must implement IPublishedContent");
    
    public override Task ExecuteAsync()
    {
        return Task.CompletedTask;
    }
}

Note that this gets an actual PublidhedValueFallback instead of the NoopPublishedValueFallback.

I will create a PR that makes the NoopPublishedValueFallback implement the new interface member.