Infinite recursion when Content Picker Field references its own parent item with displaying shape override

[Piedone]

Describe the bug

You can create an infinite recursion if you pick the parent item itself in a Content Picker Field.

To Reproduce

Steps to reproduce the behavior:

1. Add Content Picker Field to a content type, allowing the content type itself to be selected (e.g. you add it to Page, and let Page items be picked too).
2. Create a content item, publish, edit again, pick the content item itself, publish.
3. By default, this doesn't cause an issue, because the ContentPicker shape only lists the display texts of the picked items. However, if you have an override that DisplayAsync()s the picked items, see below, you can produce an infinite loop, crashing the process.

@model OrchardCore.ContentFields.ViewModels.DisplayContentPickerFieldViewModel
@using OrchardCore.ContentManagement
@using OrchardCore.ContentManagement.Display
@using OrchardCore.DisplayManagement.ModelBinding
@using OrchardCore.Mvc.Utilities
@using OrchardCore.ContentManagement.Metadata.Models

@inject IContentManager ContentManager
@inject IContentItemDisplayManager DisplayManager
@inject IUpdateModelAccessor UpdateModelAccessor

@{
    var contentItems = await ContentManager.GetAsync(Model.ContentItemIds);

    foreach (var contentItem in contentItems)
    {
        <span>This is new:</span>
        @(await DisplayAsync(await DisplayManager.BuildDisplayAsync(contentItem, UpdateModelAccessor.ModelUpdater)))
    }
}

Latest main (8e3c8180dbe3d8eca792767e7e68f87fc89982ea).

Expected behavior

This is clearly a misconfiguration that can't produce much sensible, but still, the app shouldn't crash. So, e.g.:

• An error message is displayed on the frontend in place of the picked items.
• Don't let such picked items be saved in the first place. This might be just part of the solution though, since due to indirections (picked item within picked item...) and dynamic inclusions this can't necessarily be determined.

Screenshots

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[sebastienros]

In Fluid there is MaxSteps and MaxRecursion to limit the execution of templates.

[github-actions[bot]]

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