Multi-target netstandard2.0 and net8.0 with regex fallback

Agent-Logs-Url: https://github.com/devlooped/Schematron/sessions/f32a5ddd-99bd-47c6-b680-474fbf82aa8e

Co-authored-by: kzu <169707+kzu@users.noreply.github.com>

Author: Copilot

src/Schematron/Schematron.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <AssemblyName>Schematron</AssemblyName>
     <RootNamespace>Schematron</RootNamespace>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageId>Schematron.NET</PackageId>
     <LangVersion>Latest</LangVersion>
@@ -13,4 +13,11 @@
     <InternalsVisibleTo Include="Schematron.Tests" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="PolySharp" Version="1.15.0">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
 </Project>

src/Schematron/TagExpressions.cs

@@ -5,6 +5,7 @@ namespace Schematron;
 /// <summary />
 partial class TagExpressions
 {
+#if NET8_0_OR_GREATER
     /// <summary>
     /// The compiled regular expression to replace the special <c>name</c> and <c>value</c> tags inside a message.
     /// </summary>
@@ -32,8 +33,42 @@ partial class TagExpressions
 
     // Closing elements don't have an expanded xmlns so they will be matched too.
     // TODO: improve this to avoid removing non-schematron closing elements.
-    // Pattern derived from Schema.LegacyNamespace and Schema.IsoNamespace (with Regex.Escape applied).
+    // Pattern derived from Regex.Escape(Schema.LegacyNamespace) and Regex.Escape(Schema.IsoNamespace).
+    // If those constants ever change, update the hardcoded escaped values here to match.
     [GeneratedRegex(@"<.*\bxmlns\b[^\s]*(?:http://www\.ascc\.net/xml/schematron|http://purl\.oclc\.org/dsdl/schematron)[^>]*>|</[^>]*>")]
     public static partial Regex AllSchematron();
+#else
+    /// <summary>
+    /// The compiled regular expression to replace the special <c>name</c> and <c>value</c> tags inside a message.
+    /// </summary>
+    /// <remarks>
+    /// Replaces each instance of <c>name</c> and <c>value</c>tags with the value in the current context element.
+    /// </remarks>
+    // The element declarations can contain the namespace if expanded in a loaded document.
+    static readonly Regex _nameValueOf = new Regex(@"<[^\s>]*\b(name|value-of)\b[^>]*/>", RegexOptions.Compiled);
+    public static Regex NameValueOf() => _nameValueOf;
+
+    static readonly Regex _emph = new Regex(@"<[^\s>]*\bemph\b[^>]*>", RegexOptions.Compiled);
+    public static Regex Emph() => _emph;
+
+    static readonly Regex _dir = new Regex(@"<[^\s]*\bdir\b[^>]*>", RegexOptions.Compiled);
+    public static Regex Dir() => _dir;
+
+    static readonly Regex _span = new Regex(@"<[^\s]*\bspan\b[^>]*>", RegexOptions.Compiled);
+    public static Regex Span() => _span;
+
+    static readonly Regex _para = new Regex(@"<[^\s]*\bp\b[^>]*>", RegexOptions.Compiled);
+    public static Regex Para() => _para;
+
+    static readonly Regex _any = new Regex(@"<[^\s]*[^>]*>", RegexOptions.Compiled);
+    public static Regex Any() => _any;
+
+    // Closing elements don't have an expanded xmlns so they will be matched too.
+    // TODO: improve this to avoid removing non-schematron closing elements.
+    static readonly Regex _allSchematron = new Regex(
+        @"<.*\bxmlns\b[^\s]*(?:" + Regex.Escape(Schema.LegacyNamespace) + "|" + Regex.Escape(Schema.IsoNamespace) + @")[^>]*>|</[^>]*>",
+        RegexOptions.Compiled);
+    public static Regex AllSchematron() => _allSchematron;
+#endif
 }