MarkupMatches partially broken since 1.16.2 (regression)

Describe the bug

Comparison of the markup of a rendered component is broken for medium complex markup since version 1.16.2.

Example: Here’s the actual markup that got rendered (taken from cut.Markup):

<div class="main" b-l9zz05p28t><div class="pane master-pane" b-l9zz05p28t><div class="header" b-l9zz05p28t><div class="zui-header" style="font: var(--zui-typography-h2); " b-9gghzsuirm>Custom Metadata Definitions</div>
            <zui-button id="add-button" emphasis="primary-highlight" blazor:onclick="1" disabled style="width: 100%;">Add new<zui-icon-symbols-plus slot="icon" size="s32"></zui-icon-symbols-plus></zui-button></div><div style="display: flex; align-items: center; align-self: start;"><zui-progress-ring size="s16" emphasis="highlight" mode="activity" style="margin-right: 5px;"></zui-progress-ring>
    <em>Loading...</em></div></div>
    <div class="details-pane-outer" b-l9zz05p28t><div class="placeholder-container" b-nfzpgxci6j><div class="placeholder-header" b-nfzpgxci6j>No custom metadata definition selected</div>
    <div class="placeholder-body" b-nfzpgxci6j>Please select a custom metadata definition from the list to view the details</div></div></div></div>

And this is the markup that it is compared to using cut.MarkupMatches. This worked up to bUnit version <= 1.15.5.

<div class="main">
                    <div class="pane master-pane">
                        <div class="header">
                            <div class="zui-header" style="font: var(--zui-typography-h2);">Custom Metadata Definitions</div>
                            <zui-button id="add-button" emphasis="primary-highlight" disabled style="width: 100%;">
                                Add new
                                <zui-icon-symbols-plus slot="icon" size="s32"></zui-icon-symbols-plus>
                            </zui-button>
                        </div>
                        <div diff:ignoreAttributes>
                            <zui-progress-ring diff:ignoreAttributes></zui-progress-ring>
                            <em>Loading...</em>
                        </div>
                    </div>
                    <div class="details-pane-outer">
                        <div class="placeholder-container" diff:ignoreChildren></div>
                    </div>
                </div>

Since version 1.16.2 it fails with the following error message: An attribute source map cannot be created unless a element comparison source is provided. (Parameter ‘elementSource’)

CustomMetadataPageTests.Render_ItemsIsNull_ShouldRenderBasicLayout threw exception: 
System.ArgumentException: An attribute source map cannot be created unless a element comparison source is provided. (Parameter 'elementSource')
    at AngleSharp.Diffing.Core.SourceMap..ctor(ComparisonSource& elementSource)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElementAttributes(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElement(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareNode(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.<CompareNodes>b__11_0(Comparison comparison)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElement(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareNode(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.<CompareNodes>b__11_0(Comparison comparison)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElement(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareNode(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.<CompareNodes>b__11_0(Comparison comparison)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElement(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareNode(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.<CompareNodes>b__11_0(Comparison comparison)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareElement(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.CompareNode(Comparison& comparison)
   at AngleSharp.Diffing.Core.HtmlDifferenceEngine.<CompareNodes>b__11_0(Comparison comparison)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.SparseArrayBuilder`1.ReserveOrAdd(IEnumerable`1 items)
   at System.Linq.Enumerable.Concat2Iterator`1.ToArray()
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Bunit.CompareToExtensions.CompareTo(INodeList actual, INodeList expected) in /_/src/bunit.web/Asserting/CompareToExtensions.cs:line 106
   at Bunit.MarkupMatchesAssertExtensions.MarkupMatches(INodeList actual, INodeList expected, String userMessage) in /_/src/bunit.web/Asserting/MarkupMatchesAssertExtensions.cs:line 234
   at Bunit.MarkupMatchesAssertExtensions.MarkupMatches(IRenderedFragment actual, String expected, String userMessage) in /_/src/bunit.web/Asserting/MarkupMatchesAssertExtensions.cs:line 113
   at CustomMetadataPageTests.Render_ItemsIsNull_ShouldRenderBasicLayout()

Expected behavior:

It should work the same way as before.

Version info:

• bUnit version: 1.16.2 and higher (checked up to latest available 1.18.4)
• .NET Runtime and Blazor version: 6.0.16
• OS type and version: Windows 10

Additional context:

I first assumed this problem was caused by the upgrade of AngleSharp.Diffing, but bUnit 1.15.5 and 1.16.2 both use AngleSharp.Diffing 0.17.1. So it seems to be a problem somewhere within bUnit.

[linkdotnet]

There should be another preview version available soon. I would love to get your feedback on the newest version

[linkdotnet]

@candritzky release is out! You can now use the stable 1.19 version.