Merge pull request #20 from fredrikhr/extended-nullable

Skip.If nullable-reference type post-condition annotations

Author: AArnott

Directory.Build.props

@@ -29,6 +29,7 @@
     <PackageReference Include="Nerdbank.GitVersioning" Version="3.1.74" PrivateAssets="all" />
     <PackageReference Include="Microsoft.Net.Compilers.Toolset" Version="3.5.0" PrivateAssets="all" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.164" PrivateAssets="all" />
+    <PackageReference Include="Nullable" Version="1.2.1" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>
     <AdditionalFiles Include="$(MSBuildThisFileDirectory)stylecop.json" />

src/Xunit.SkippableFact/Skip.cs

@@ -3,6 +3,8 @@
 
 namespace Xunit
 {
+    using System.Diagnostics.CodeAnalysis;
+
     /// <summary>
     /// Static methods for dynamically skipping tests identified with
     /// the <see cref="SkippableFactAttribute"/>.
@@ -14,7 +16,9 @@ public static class Skip
         /// </summary>
         /// <param name="condition">The condition that must evaluate to <c>true</c> for the test to be skipped.</param>
         /// <param name="reason">The explanation for why the test is skipped.</param>
-        public static void If(bool condition, string? reason = null)
+        public static void If(
+            [DoesNotReturnIf(true)] bool condition,
+            string? reason = null)
         {
             if (condition)
             {
@@ -27,7 +31,9 @@ public static void If(bool condition, string? reason = null)
         /// </summary>
         /// <param name="condition">The condition that must evaluate to <c>false</c> for the test to be skipped.</param>
         /// <param name="reason">The explanation for why the test is skipped.</param>
-        public static void IfNot(bool condition, string? reason = null)
+        public static void IfNot(
+            [DoesNotReturnIf(false)] bool condition,
+            string? reason = null)
         {
             Skip.If(!condition, reason);
         }

src/Xunit.SkippableFact/Xunit.SkippableFact.csproj

@@ -11,7 +11,7 @@
     <None Update="xunit.runner.json">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
-  </ItemGroup>  
+  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Validation" Version="2.4.18" PrivateAssets="compile;contentfiles;analyzers;build" />
     <PackageReference Include="xunit.extensibility.execution" Version="2.1.0" Condition=" '$(TargetFramework)' == 'net45' " />

test/Xunit.SkippableFact.Tests/SkipTests.cs

@@ -48,5 +48,37 @@ public void IfNot_WithReason()
                 Assert.Equal(reason, ex.Message);
             }
         }
+
+        [Fact]
+        public void If_SupportsNullableReferenceTypesPostCondition()
+        {
+            // Provoke a possibly null value that is not detectable through
+            // static analysis
+            string? value =
+                int.Parse("42", System.Globalization.CultureInfo.InvariantCulture) == 42
+                ? "Not null"
+                : null;
+
+            Skip.If(value is null);
+
+            // Does not trigger a nullable reference type warning
+            _ = value.Substring(0);
+        }
+
+        [Fact]
+        public void IfNot_SupportsNullableReferenceTypesPostCondition()
+        {
+            // Provoke a possibly null value that is not detectable through
+            // static analysis
+            string? value =
+                int.Parse("42", System.Globalization.CultureInfo.InvariantCulture) == 42
+                ? "Not null"
+                : null;
+
+            Skip.IfNot(value is object);
+
+            // Does not trigger a nullable reference type warning
+            _ = value.Substring(0);
+        }
     }
 }