feat: Self closing comparer. (#32)

* Self closing comparer.

* Implement suggestions.

* Added changelog entry.

* Update CHANGELOG.md

* Update CHANGELOG.md

* add IsKeepingSourceReferences to diffbuilder too

---------

Co-authored-by: Egil Hansen <[email protected]>

Author: SebastianStehle

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.18.0
+
+- Added a new comparer, which ensures element tags are closed the same way, e.g. `<br> and <br />` would not be considered equal, but `<br>` and `<br>` would be.
+
 # 0.17.1
 
 Released on Friday, February 3, 2023.

src/AngleSharp.Diffing.Tests/DiffingTestFixture.cs

@@ -11,7 +11,11 @@ public class DiffingTestFixture
 
         public DiffingTestFixture()
         {
-            var config = Configuration.Default.WithCss();
+            // Create a custom config with a parser to allow access to the source reference from the AST.
+            var config = Configuration.Default
+                .WithCss()
+                .With<IHtmlParser>(ctx => new HtmlParser(new HtmlParserOptions { IsKeepingSourceReferences = true, IsScripting = ctx?.IsScripting() ?? false }, ctx));
+
             _context = BrowsingContext.New(config);
             _htmlParser = _context.GetService<IHtmlParser>();
             _document = _context.OpenNewAsync().Result;

src/AngleSharp.Diffing.Tests/Strategies/ElementStrategies/ElementClosingComparerTest.cs

@@ -0,0 +1,41 @@
+using System.Linq;
+
+using AngleSharp.Diffing.Core;
+
+using Shouldly;
+
+using Xunit;
+
+namespace AngleSharp.Diffing.Strategies.ElementStrategies
+{
+    public class ElementClosingComparerTest : DiffingTestBase
+    {
+        public ElementClosingComparerTest(DiffingTestFixture fixture) : base(fixture)
+        {
+        }
+
+        [Fact(DisplayName = "When control and test nodes have are both self closed, the result is Same")]
+        public void Test001()
+        {
+            var comparison = ToComparison("<v:image />", "<v:image />");
+
+            ElementClosingComparer.Compare(comparison, CompareResult.Unknown).ShouldBe(CompareResult.Same);
+        }
+
+        [Fact(DisplayName = "When control and test nodes have are both not self closed, the result is Same")]
+        public void Test002()
+        {
+            var comparison = ToComparison("<v:image />", "<v:image />");
+
+            ElementClosingComparer.Compare(comparison, CompareResult.Unknown).ShouldBe(CompareResult.Same);
+        }
+
+        [Fact(DisplayName = "When either control or test node is self closed, the result is Same")]
+        public void Test003()
+        {
+            var comparison = ToComparison("<v:image />", "<v:image>");
+
+            ElementClosingComparer.Compare(comparison, CompareResult.Unknown).ShouldBe(CompareResult.Different);
+        }
+    }
+}

src/AngleSharp.Diffing/DiffBuilder.cs

@@ -34,9 +34,19 @@ public class DiffBuilder
         private DiffBuilder(string control)
         {
             Control = control;
-            var config = Configuration.Default.WithCss();
+
+            // Create a custom config with a parser to allow access to the source reference from the AST.
+            var config = Configuration.Default
+                .WithCss()
+                .With<IHtmlParser>(ctx => new HtmlParser(new HtmlParserOptions
+                {
+                    IsKeepingSourceReferences = true,
+                    IsScripting = ctx?.IsScripting() ?? false
+                }, ctx));
+
             _context = BrowsingContext.New(config);
-            _htmlParser = _context.GetService<IHtmlParser>() ?? throw new InvalidOperationException("No IHtmlParser registered in the default AngleSharp browsing context.");
+            _htmlParser = _context.GetService<IHtmlParser>()
+                ?? throw new InvalidOperationException("No IHtmlParser registered in the default AngleSharp browsing context.");
             _document = _context.OpenNewAsync().Result;
         }
 

src/AngleSharp.Diffing/HtmlDiffer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+
 using AngleSharp.Diffing.Core;
 using AngleSharp.Diffing.Extensions;
 using AngleSharp.Dom;
@@ -24,9 +25,19 @@ public class HtmlDiffer
         public HtmlDiffer(IDiffingStrategy diffingStrategy)
         {
             _diffingStrategy = diffingStrategy ?? throw new ArgumentNullException(nameof(diffingStrategy));
-            var config = Configuration.Default.WithCss();
+
+            // Create a custom config with a parser to allow access to the source reference from the AST.
+            var config = Configuration.Default
+                .WithCss()
+                .With<IHtmlParser>(ctx => new HtmlParser(new HtmlParserOptions
+                {
+                    IsKeepingSourceReferences = true,
+                    IsScripting = ctx?.IsScripting() ?? false
+                }, ctx));
+
             _context = BrowsingContext.New(config);
-            _htmlParser = _context.GetService<IHtmlParser>() ?? throw new InvalidOperationException("No IHtmlParser registered in the default AngleSharp browsing context.");
+            _htmlParser = _context.GetService<IHtmlParser>()
+                ?? throw new InvalidOperationException("No IHtmlParser registered in the default AngleSharp browsing context.");
             _document = _context.OpenNewAsync().Result;
         }
 

src/AngleSharp.Diffing/Strategies/ElementStrategies/DiffingStrategyPipelineBuilderExtensions.cs

@@ -14,6 +14,15 @@ public static IDiffingStrategyCollection AddElementComparer(this IDiffingStrateg
             return builder;
         }
 
+        /// <summary>
+        /// Adds an element comparer that ensures element tags are closed the same way, e.g. `&lt;br&gt;` and `&lt;br /&gt;` would not be considered equal, but `&lt;br&gt;` and `&lt;br&gt;` would be.
+        /// </summary>
+        public static IDiffingStrategyCollection AddElementClosingComparer(this IDiffingStrategyCollection builder)
+        {
+            builder.AddComparer(ElementClosingComparer.Compare, StrategyType.Generalized);
+            return builder;
+        }
+
         /// <summary>
         /// Enables the CSS-selector matcher strategy during diffing.
         /// </summary>

src/AngleSharp.Diffing/Strategies/ElementStrategies/ElementClosingComparer.cs

@@ -0,0 +1,29 @@
+using AngleSharp.Diffing.Core;
+using AngleSharp.Dom;
+using AngleSharp.Html.Parser.Tokens;
+
+namespace AngleSharp.Diffing.Strategies.ElementStrategies
+{
+    /// <summary>
+    /// Represents the element closing comparer strategy.
+    /// </summary>
+    public static class ElementClosingComparer
+    {
+        /// <summary>
+        /// The element comparer closing strategy.
+        /// </summary>
+        public static CompareResult Compare(in Comparison comparison, CompareResult currentDecision)
+        {
+            if (currentDecision == CompareResult.Skip)
+                return currentDecision;
+
+            if (comparison.Test.Node is not IElement testElement || testElement.SourceReference is not HtmlTagToken testTag)
+                return currentDecision;
+
+            if (comparison.Control.Node is not IElement controlElement || controlElement.SourceReference is not HtmlTagToken controlTag)
+                return currentDecision;
+
+            return testTag.IsSelfClosing == controlTag.IsSelfClosing ? CompareResult.Same : CompareResult.Different;
+        }
+    }
+}