Nested Editor<T> crashing because of bug in HtmlFieldPrefix.Combine method

[sal-versij]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Nesting more than 2 Editor leads to an exception

Expected Behavior

It should work properly and not throw any exception

Steps To Reproduce

https://github.com/sal-versij/NestedEditorTCrash

Just visit the home

Exceptions (if any)

Unhandled exception rendering component: Object reference not set to an instance of an object.
    System.NullReferenceException: Object reference not set to an instance of an object.
       at Microsoft.AspNetCore.Components.Forms.ExpressionFormatter.FormatLambda(LambdaExpression expression, String prefix)
       at Microsoft.AspNetCore.Components.Forms.HtmlFieldPrefix.GetFieldName(LambdaExpression expression)
       at Microsoft.AspNetCore.Components.Forms.InputBase`1.get_NameAttributeValue()
       at Microsoft.AspNetCore.Components.Forms.InputNumber`1.BuildRenderTree(RenderTreeBuilder builder)
       at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)

.NET Version

8.0.100

Anything else?

After searching why this happens, I've found that in HtmlFieldPrefix.cs:23 the loop is not actually looping through the whole _rest because it uses restLength - 1 instead of length - 1 or restLength itself, thus it's ignoring the last element of _rest that is left as the default value in expressions: null, this is propagated to the inputs inside the innermost editor that, when executing GetFieldName(...) throws because _rest of the input contains a null value passed to ExpressionFormatter.FormatLambda that throws NullReferenceException at ExpressionFormatter.cs:41

[sal-versij]

Is there any update on the state for a fix of this issue?

[sgarnovsky]

Got stuck with the same issue.
Feel like it is like a feature (to limit using Editor w/o nesting), but there is no other way to handle it as all related to HtmlFieldPrefix code is internal.

See, a misprint is still here: https://github.com/dotnet/aspnetcore/blame/de68d4212113859604d9e57cf7d674b167a8a317/src/Components/Web/src/Forms/HtmlFieldPrefix.cs#L23

public HtmlFieldPrefix Combine(LambdaExpression other)
    {
        var restLength = _rest?.Length ?? 0;
        var length = restLength + 1;
        var expressions = new LambdaExpression[length];
        //for (var i = 0; i < restLength - 1; i++)
        for (var i = 0; i < **length** - 1; i++)
        {
            expressions[i] = _rest![i];
        }

        expressions[length - 1] = other;

        return new HtmlFieldPrefix(initial, expressions);
    }

A fix should be pretty easy, just use a "length - 1" in a for loop above.

How we can make to speed up applying a fix for this issue?

[sgarnovsky]

.Net 9 RC still has this bug...
https://github.com/dotnet/aspnetcore/blob/v9.0.0-rc.2.24474.3/src/Components/Web/src/Forms/HtmlFieldPrefix.cs

This is frustrating... So a powerful feature but can't be used fully due to this simple issue.