Doc gen: use comment for required .net version pragma

Author: dtchepak

docs/help/argument-matchers/index.md

@@ -98,7 +98,7 @@ Assert.That(formatter.Format(null), Is.Not.EqualTo("matched"));
 _[Since v6.0; .NET6 and above]_ An argument of type `T` can also be conditionally matched using `ArgMatchers.Matching`.
 
 ```csharp
-#if NET6_0_OR_GREATER
+// !!! Requires .NET6 or greater
 
 // With `using static NSubstitute.ArgMatchers`
 calculator.Add(1, -10);
@@ -111,8 +111,6 @@ calculator
     .Add(1, Arg.Is(Matching<int>(x => new[] {-2,-5,-10}.Contains(x))));
 //Did not receive call with first arg greater than 10:
 calculator.DidNotReceive().Add(Arg.Is(Matching<int>(x => x > 10)), -10);
-
-#endif
 ```
 
 

tests/NSubstitute.Documentation.Tests.Generator/DocumentationTestsGenerator.cs

@@ -9,6 +9,7 @@ namespace NSubstitute.Documentation.Tests.Generator;
 public sealed class DocumentationTestsGenerator : IIncrementalGenerator
 {
     private static readonly Regex markdownCodeRegex = new("```(?<tag>\\w+)(?<contents>(?s:.*?))```?");
+    private static readonly Regex requiresPragmaRegex = new("// !!! Requires .NET(?<version>\\d) or greater");
     private static readonly Regex typeOrTestDeclarationRegex = new(@"(\[Test\]|(public |private |protected )?(class |interface )\w+\s*\{)");
 
     public void Initialize(IncrementalGeneratorInitializationContext context)
@@ -74,12 +75,18 @@ public sealed class {{testsClassName}}
 
         for (int testCaseNumber = 0; testCaseNumber < snippets.Count; testCaseNumber++)
         {
+            var snippet = snippets[testCaseNumber];
+            var requiredVersion = RequiresVersion(snippet);
+            var requiredVersionPragma = requiredVersion != null ? $"#if NET{{requiredVersion}}_0_OR_GREATER" : null;
+            var closeRequiredVersionPragma = requiredVersion != null ? "#endif" : null;
             testClassContent.AppendLine(
                 $$"""
                 [Test]
                 public void Test{{testCaseNumber}}()
                 {
-                    {{snippets[testCaseNumber]}}
+                    {{requiredVersionPragma}}
+                    {{snippet}}
+                    {{closeRequiredVersionPragma}}
                 }
                 """);
         }
@@ -89,6 +96,16 @@ public sealed class {{testsClassName}}
         return testClassContent.ToString();
     }
 
+    private static int? RequiresVersion(string snippet)
+    {
+        var version = requiresPragmaRegex.Match(snippet).Groups["version"]?.Value;
+        if (version == null)
+        {
+            return null;
+        }
+        return int.Parse(version);
+    }
+
     private static void ParseMarkdownCodeBlocks(AdditionalText markdownFile, out List<string> declarations, out List<string> snippets)
     {
         var markdownContent = markdownFile.GetText().ToString();