feat: re-support net46 and netstandard2.0 targets

.github/workflows/ci.yaml

@@ -3,36 +3,64 @@ on:
   push:
     branches:
       - master
+      - 5.x
   pull_request:
     branches:
       - master
+      - 5.x
 
 env:
   DOTNET_CLI_TELEMETRY_OPTOUT: 1
   DOTNET_SKIP_FIRST_TIME_EXPERIENCE: 1
 
 jobs:
-  job:
-    strategy:
-      matrix:
-        include:
-          - os: ubuntu-latest
-            artifact-name: Linux
-          #- os: macos-11
-          # artifact-name: Darwin
-          #- os: windows-2022
-          #  artifact-name: Win64 
-    runs-on: ${{ matrix.os }} 
-    continue-on-error: true
+  # Compiles every target framework (including the downlevel net46 and netstandard2.0
+  # builds) and runs the full test suite on every framework that can execute on Linux.
+  # net6.0 resolves the library's netstandard2.0 build, so that build is fully tested.
+  build-and-test:
+    runs-on: ubuntu-latest
     steps:
-      - name: checkout repo
+      - name: Checkout repo
         uses: actions/checkout@v4
-      - name: Install .NET 9.0.x
+      - name: Install .NET SDKs
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 9.0.x
+          dotnet-version: |
+            6.0.x
+            8.0.x
+            9.0.x
+            10.0.x
       - name: Display dotnet info
-        run: dotnet --list-sdks  
-      - name: Run tests
-        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net9.0
+        run: dotnet --list-sdks
+      # Build all target frameworks: net46;netstandard2.0;net8.0;net9.0;net10.0.
+      # net46 is built on Linux via the Microsoft.NETFramework.ReferenceAssemblies package.
+      - name: Build library (all target frameworks)
+        run: dotnet build src/ReverseMarkdown/ReverseMarkdown.csproj -c Release
+      - name: Test net6.0 (netstandard2.0 build)
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net6.0 -c Release
+      - name: Test net8.0
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net8.0 -c Release
+      - name: Test net9.0
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net9.0 -c Release
+      - name: Test net10.0
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net10.0 -c Release
 
+  # Runs the full suite on real .NET Framework so the net46 build is exercised at runtime
+  # (net48 -> library net46 build). Windows-only, since .NET Framework cannot run on Linux.
+  net-framework:
+    runs-on: windows-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+      - name: Install .NET SDKs
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: |
+            6.0.x
+            9.0.x
+      - name: Display dotnet info
+        run: dotnet --list-sdks
+      - name: Test net48 (net46 build)
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net48 -c Release
+      - name: Test net6.0 (netstandard2.0 build)
+        run: dotnet test src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj --framework net6.0 -c Release

.github/workflows/nuget-publish.yaml

@@ -19,11 +19,16 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Install .NET 9.0.x
+      - name: Install .NET SDKs
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 9.0.x
+          dotnet-version: |
+            8.0.x
+            9.0.x
+            10.0.x
 
+      # Packs all target frameworks: net46;netstandard2.0;net8.0;net9.0;net10.0.
+      # net46 is built on Linux via the Microsoft.NETFramework.ReferenceAssemblies package.
       - name: Run Pack
         run: dotnet pack src/ReverseMarkdown/ReverseMarkdown.csproj -c Release
         shell: bash

src/ReverseMarkdown.Test/ConverterTests.cs

@@ -4,8 +4,6 @@
 using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
-using VerifyTests;
-using VerifyXunit;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -14,13 +12,24 @@ namespace ReverseMarkdown.Test
     public class ConverterTests
     {
         private readonly ITestOutputHelper _testOutputHelper;
-        private readonly VerifySettings _verifySettings;
 
         public ConverterTests(ITestOutputHelper testOutputHelper)
         {
             _testOutputHelper = testOutputHelper;
-            _verifySettings = new VerifySettings();
-            _verifySettings.DisableRequireUniquePrefix();
+        }
+
+        // Reads a checked-in snapshot file (formerly compared by Verify) and normalises
+        // line endings + trailing newline so it can be asserted on every target framework.
+        private static string LoadVerified(string testName, string extension)
+        {
+            var path = Path.Combine(GetProjectDirectory().FullName,
+                $"ConverterTests.{testName}.verified.{extension}");
+            return Normalize(File.ReadAllText(path));
+        }
+
+        private static string Normalize(string text)
+        {
+            return text.Replace("\r\n", "\n").Replace("\r", "\n").TrimEnd('\n');
         }
 
         private static readonly Lazy<Dictionary<string, string>> CaseHtmlById = new(() =>
@@ -197,7 +206,7 @@ public void WhenOutputLineEndingConfigured_ThenNormalizeOutputLineEndings()
 
             var result = converter.Convert(html);
 
-            Assert.Equal(result, result.ReplaceLineEndings("\n"));
+            Assert.Equal(result, result.Replace("\r\n", "\n").Replace("\r", "\n"));
             Assert.DoesNotContain("\r", result);
         }
 
@@ -591,15 +600,14 @@ public void WhenBase64ImgTag_WithSaveToFileAndNonExistentDirectory_ThenCreateDir
 
 
         [Fact]
-        public Task When_Underline_Tag_With_AliasConverter_Register_ThenConvertToItalics()
+        public void When_Underline_Tag_With_AliasConverter_Register_ThenConvertToItalics()
         {
             var html = LoadHtml("Underline_Tag_Alias");
             var converter = new Converter();
             converter.Register("u", new ReverseMarkdown.Converters.AliasConverter(converter, "em"));
             var result = converter.Convert(html);
-            var settings = new VerifySettings();
-            settings.DisableRequireUniquePrefix();
-            return Verifier.Verify(result, settings: settings, extension: "md");
+            var expected = LoadVerified(nameof(When_Underline_Tag_With_AliasConverter_Register_ThenConvertToItalics), "md");
+            Assert.Equal(expected, Normalize(result));
         }
 
 
@@ -611,16 +619,16 @@ public Task When_Underline_Tag_With_AliasConverter_Register_ThenConvertToItalics
 
 
         [Fact]
-        public Task Check_Converter_With_Unknown_Tag_Raise_Option()
+        public void Check_Converter_With_Unknown_Tag_Raise_Option()
         {
             var html = LoadHtml("Unknown_Tag_Raise");
             var config = new Config
             {
                 UnknownTags = Config.UnknownTagsOption.Raise
             };
             var converter = new Converter(config);
-            return Verifier.Throws(() => converter.Convert(html), settings: _verifySettings)
-                .IgnoreMember<Exception>(e => e.StackTrace);
+            var ex = Assert.Throws<UnknownTagException>(() => converter.Convert(html));
+            Assert.Equal("Unknown tag: unknown-tag", ex.Message);
         }
 
 
@@ -936,7 +944,10 @@ private static IEnumerable<CaseData> ApplyTagFilter(IEnumerable<CaseData> cases)
                 return cases;
             }
 
-            var tags = filter.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+            var tags = filter.Split(',')
+                .Select(tag => tag.Trim())
+                .Where(tag => tag.Length > 0)
+                .ToArray();
             return cases.Where(testCase => testCase.Tags.Any(tag => tags.Contains(tag, StringComparer.OrdinalIgnoreCase)));
         }
 
@@ -958,11 +969,11 @@ private static string LoadExpected(CaseData testCase)
 
             var expected = File.ReadAllText(path);
             if (expected.EndsWith("\r\n", StringComparison.Ordinal)) {
-                return expected[..^2];
+                return expected.Substring(0, expected.Length - 2);
             }
 
             if (expected.EndsWith("\n", StringComparison.Ordinal)) {
-                return expected[..^1];
+                return expected.Substring(0, expected.Length - 1);
             }
 
             return expected;

src/ReverseMarkdown.Test/ReverseMarkdown.Test.csproj

@@ -1,23 +1,51 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
+    <!--
+      The suite runs on every framework the library supports, so the downlevel builds
+      (net48 -> net46, net6.0 -> netstandard2.0) get full runtime coverage. Verify was
+      removed in favour of plain assertions / checked-in snapshot files so the tests can
+      run on net48 and net6.0 without framework-specific tooling.
+    -->
+    <TargetFrameworks>net48;net6.0;net8.0;net9.0;net10.0</TargetFrameworks>
     <IsTestProject>true</IsTestProject>
     <LangVersion>preview</LangVersion>
+    <SuppressTfmSupportBuildErrors>true</SuppressTfmSupportBuildErrors>
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="Markdig" Version="1.0.0" />
+  </ItemGroup>
+
+  <!-- Modern frameworks: latest test tooling. -->
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0' or '$(TargetFramework)' == 'net9.0' or '$(TargetFramework)' == 'net10.0'">
     <PackageReference Include="coverlet.collector" Version="8.0.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
-    <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="Verify.Xunit" Version="31.12.5" />
-    <PackageReference Include="Markdig" Version="1.0.0" />
+  </ItemGroup>
+
+  <!-- Downlevel frameworks: last test tooling that supports the net48/net6.0 hosts.
+       coverlet.collector is intentionally omitted here: its transitive
+       Microsoft.Diagnostics.NETCore.Client wants Microsoft.Bcl.AsyncInterfaces 9.0,
+       which isn't deployed on the net6.0 host and silently breaks test discovery. -->
+  <ItemGroup Condition="'$(TargetFramework)' == 'net48' or '$(TargetFramework)' == 'net6.0'">
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <!-- net48 lacks an in-box System.Text.Json and .NET Framework reference assemblies. -->
+  <ItemGroup Condition="'$(TargetFramework)' == 'net48'">
+    <PackageReference Include="System.Text.Json" Version="8.0.5" />
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>
@@ -44,12 +72,6 @@
     <None Update="ConverterTests.Bug294_Table_bug_with_row_superfluous_newlines.verified.md">
       <DependentUpon>ConverterTests.cs</DependentUpon>
     </None>
-    <None Update="ConverterTests.Check_Converter_With_Unknown_Tag_Raise_Option.verified.txt">
-      <DependentUpon>ConverterTests.cs</DependentUpon>
-    </None>
-    <None Update="ConverterTests.Check_Converter_With_Unknown_Tag_Raise_Option.DotNet6_0.received.txt">
-      <DependentUpon>ConverterTests.cs</DependentUpon>
-    </None>
     <None Update="ConverterTests.When_Anchor_Text_with_Underscore_Do_Not_Escape.verified.md">
       <DependentUpon>ConverterTests.cs</DependentUpon>
     </None>

src/ReverseMarkdown.Test/Snippets.cs

@@ -1,13 +1,11 @@
 using System;
-using System.Threading.Tasks;
 using ReverseMarkdown;
-using VerifyXunit;
 using Xunit;
 
 public class Snippets
 {
     [Fact]
-    public async Task Usage()
+    public void Usage()
     {
         #region Usage
 
@@ -19,7 +17,7 @@ public async Task Usage()
 
         #endregion
 
-        await Verifier.Verify(result);
+        Assert.Equal("This a sample **paragraph** from [my site](http://test.com)", result);
     }
 
     [Fact]

src/ReverseMarkdown/Cleaner.cs

@@ -6,6 +6,7 @@
 namespace ReverseMarkdown;
 
 public static partial class Cleaner {
+#if NET7_0_OR_GREATER
     [GeneratedRegex(@"\*(\s\*)+")]
     private static partial Regex SlackBoldCleaner();
 
@@ -14,6 +15,16 @@ public static partial class Cleaner {
 
     [GeneratedRegex(@"[\u0020\u00A0]")]
     private static partial Regex NonBreakingSpaces();
+#else
+    private static readonly Regex _slackBoldCleaner = new(@"\*(\s\*)+", RegexOptions.Compiled);
+    private static Regex SlackBoldCleaner() => _slackBoldCleaner;
+
+    private static readonly Regex _slackItalicCleaner = new(@"_(\s_)+", RegexOptions.Compiled);
+    private static Regex SlackItalicCleaner() => _slackItalicCleaner;
+
+    private static readonly Regex _nonBreakingSpaces = new(@"[\u0020\u00A0]", RegexOptions.Compiled);
+    private static Regex NonBreakingSpaces() => _nonBreakingSpaces;
+#endif
 
     private static readonly StringReplaceValues TagBorders = new() {
         ["\n\t"] = string.Empty,

src/ReverseMarkdown/Converters/Code.cs

@@ -24,9 +24,9 @@ public override void Convert(TextWriter writer, HtmlNode node)
                 var content = node.InnerHtml;
                 var fence = CreateCommonMarkCodeFence(content);
                 writer.Write(fence);
-                var needsBacktickPadding = content.Length > 0 && (content[0] == '`' || content[^1] == '`');
+                var needsBacktickPadding = content.Length > 0 && (content[0] == '`' || content[content.Length - 1] == '`');
                 var needsWhitespacePadding = content.Length > 0 &&
-                                            (char.IsWhiteSpace(content[0]) || char.IsWhiteSpace(content[^1]));
+                                            (char.IsWhiteSpace(content[0]) || char.IsWhiteSpace(content[content.Length - 1]));
                 var needsPadding = needsBacktickPadding || needsWhitespacePadding;
 
                 if (needsPadding) {

src/ReverseMarkdown/Converters/H.cs

@@ -67,7 +67,7 @@ private static string EscapeTrailingHashes(string content)
             var hashCount = content.Length - 1 - index;
             var escapedHashes = new string('#', hashCount);
             escapedHashes = escapedHashes.Replace("#", "\\#");
-            return content[..(index + 1)] + escapedHashes;
+            return content.Substring(0, index + 1) + escapedHashes;
         }
     }
 }

src/ReverseMarkdown/Converters/Pre.cs

@@ -129,8 +129,14 @@ private static string GetLanguageFromHighlightClassAttribute(HtmlNode node)
         /// Extracts class attribute syntax using: highlight-json, highlight-source-json, language-json, brush: language
         /// Returns the Language in Match.Groups[2]
         /// </summary>
+#if NET7_0_OR_GREATER
         [GeneratedRegex(@"(highlight-source-|language-|highlight-|brush:\s)([^\s]+)")]
         private static partial Regex ClassRegex();
+#else
+        private static readonly Regex _classRegex =
+            new(@"(highlight-source-|language-|highlight-|brush:\s)([^\s]+)", RegexOptions.Compiled);
+        private static Regex ClassRegex() => _classRegex;
+#endif
 
         /// <summary>
         /// Checks class attribute for language class identifiers for various