Add :only-child pseudo-class selector

See https://www.w3.org/TR/selectors-3/#only-child-pseudo Fixes #7
devlooped · Aug 31, 2021 · b6bbc91 · b6bbc91
1 parent 2427ab9
commit b6bbc91
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Showing 5 changed files with 19 additions and 1 deletion.
diff --git a/readme.md b/readme.md
@@ -26,6 +26,11 @@ At the moment, supports the following CSS selector features:
 - [Attribute selector](https://www.w3.org/TR/selectors-3/#attribute-selectors)
 - [Class selector](https://www.w3.org/TR/selectors-3/#class-html)
 - [ID selector](https://www.w3.org/TR/selectors-3/#id-selectors)
+- [Pseudo-classes](https://www.w3.org/TR/selectors-3/#pseudo-classes):
+    * [:checked](https://www.w3.org/TR/selectors-3/#checked)
+    * [:first-child](https://www.w3.org/TR/selectors-3/#first-child-pseudo)
+    * [:last-child](https://www.w3.org/TR/selectors-3/#last-child-pseudo)
+    * [:only-child](https://www.w3.org/TR/selectors-3/#only-child-pseudo)
 
 And all [combinators](https://www.w3.org/TR/selectors-3/#combinators)
 

diff --git a/src/Css/Css.cs b/src/Css/Css.cs
@@ -170,6 +170,13 @@ record LastChildSelector : SimpleSelector
     public override void Append(StringBuilder builder) => builder.Append("[not(following-sibling::*)]");
 }
 
+record OnlyChildSelector : SimpleSelector
+{
+    public static SimpleSelector Default { get; } = new OnlyChildSelector();
+    OnlyChildSelector() { }
+    public override void Append(StringBuilder builder) => builder.Append("[not(preceding-sibling::*) and not(following-sibling::*)]");
+}
+
 enum Combinator
 {
     None,

diff --git a/src/Css/Parser.cs b/src/Css/Parser.cs
@@ -81,11 +81,13 @@ class Parser
          from identifier in Span.EqualTo("checked")
             .Or(Span.EqualTo("first-child"))
             .Or(Span.EqualTo("last-child"))
+            .Or(Span.EqualTo("only-child"))
          select identifier.ToStringValue() switch 
          {
              "checked" => CheckedSelector.Default,
              "first-child" => FirstChildSelector.Default,
              "last-child" => LastChildSelector.Default,
+             "only-child" => OnlyChildSelector.Default,
              _ => throw new NotSupportedException()
          })
         .Named("checked pseudo selector");

diff --git a/src/Tests/XPathTests.cs b/src/Tests/XPathTests.cs
@@ -44,6 +44,7 @@ public void ToXPath(string css, string xpath)
     [InlineData("option:checked", "second")]
     [InlineData("div:first-child", "Warning Hello")]
     [InlineData("div:last-child", "Footer")]
+    [InlineData("h1:only-child", "Sub-header")]
     [Theory]
     public void EvaluatePageHtml(string expression, string value)
         => Assert.Equal(value, string.Join(' ', XDocument.Load("page.html")

diff --git a/src/Tests/page.html b/src/Tests/page.html
@@ -4,7 +4,10 @@
     </head>
     <body>
         <div role="alert">Warning</div>
-        <p>para</p>
+        <h1>Header</h1>
+        <p>
+            <h1>Sub-header</h1>
+        </p>
         <div class="container main flow">
             <div id="title">Hello</div>
             <span>1</span>