From 8fca65b51803f321da560e491b160e2689a797f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20H=C3=B8is=C3=A6ther=20Rasch?=
 <fredrik.rasch@gmail.com>
Date: Thu, 9 Jul 2020 12:36:59 +0200
Subject: [PATCH 1/4] Add post-condition annotations

---
 src/Xunit.SkippableFact/Skip.cs                | 18 ++++++++++++++++--
 .../Xunit.SkippableFact.csproj                 |  2 +-
 .../Xunit.SkippableFact.Tests.csproj           |  2 +-
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/Xunit.SkippableFact/Skip.cs b/src/Xunit.SkippableFact/Skip.cs
index 345e5e4..d74ab1a 100644
--- a/src/Xunit.SkippableFact/Skip.cs
+++ b/src/Xunit.SkippableFact/Skip.cs
@@ -3,6 +3,10 @@
 
 namespace Xunit
 {
+#if NETSTANDARD2_1
+    using System.Diagnostics.CodeAnalysis;
+#endif
+
     /// <summary>
     /// Static methods for dynamically skipping tests identified with
     /// the <see cref="SkippableFactAttribute"/>.
@@ -14,7 +18,12 @@ 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(
+#if NETSTANDARD2_1
+            [DoesNotReturnIf(true)]
+#endif
+            bool condition,
+            string? reason = null)
         {
             if (condition)
             {
@@ -27,7 +36,12 @@ 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(
+#if NETSTANDARD2_1
+            [DoesNotReturnIf(false)]
+#endif
+            bool condition,
+            string? reason = null)
         {
             Skip.If(!condition, reason);
         }
diff --git a/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj b/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
index 0c0e4bb..4ff32fd 100644
--- a/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
+++ b/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net45;net452</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net45;net452</TargetFrameworks>
     <RootNamespace>Xunit</RootNamespace>
 
     <Title>Dynamic test skipping for Xunit</Title>
diff --git a/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj b/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
index 4193404..f7c1072 100644
--- a/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
+++ b/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net45;net461;netcoreapp2.1</TargetFrameworks>
+    <TargetFrameworks>net45;net461;netcoreapp2.1;netcoreapp3.1</TargetFrameworks>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>

From c5c5471a273889726208d5ae3c2add7449bf3dfd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20H=C3=B8is=C3=A6ther=20Rasch?=
 <fredrik.rasch@gmail.com>
Date: Thu, 9 Jul 2020 12:50:22 +0200
Subject: [PATCH 2/4] Add NRT Post-Condition tests

---
 test/Xunit.SkippableFact.Tests/SkipTests.cs | 34 +++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/test/Xunit.SkippableFact.Tests/SkipTests.cs b/test/Xunit.SkippableFact.Tests/SkipTests.cs
index 7378263..c8b530d 100644
--- a/test/Xunit.SkippableFact.Tests/SkipTests.cs
+++ b/test/Xunit.SkippableFact.Tests/SkipTests.cs
@@ -48,5 +48,39 @@ public void IfNot_WithReason()
                 Assert.Equal(reason, ex.Message);
             }
         }
+
+#if NETCOREAPP3_1
+        [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 null));
+
+            // Does not trigger a nullable reference type warning
+            _ = value.Substring(0);
+        }
+#endif
     }
 }

From b4f4ce22fb7f7abae5f730b515b5f5cf498c6778 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20H=C3=B8is=C3=A6ther=20Rasch?=
 <fredrik.rasch@gmail.com>
Date: Thu, 9 Jul 2020 15:11:06 +0200
Subject: [PATCH 3/4] Use Nullable package for backwards compatability of
 Nullable Reference Type annotations

Adopted from https://github.com/thnetii/repository-default/blob/master/DotNet-Solution-Directory/Directory.Build.targets
---
 Directory.Build.targets         | 27 +++++++++++++++++++++++++++
 src/Xunit.SkippableFact/Skip.cs |  6 ------
 2 files changed, 27 insertions(+), 6 deletions(-)
 create mode 100644 Directory.Build.targets

diff --git a/Directory.Build.targets b/Directory.Build.targets
new file mode 100644
index 0000000..9a8d6c7
--- /dev/null
+++ b/Directory.Build.targets
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project>
+  <!-- 
+    Usage of TargetFrameworkIdentifier and _TargetFrameworkVersionWithoutV
+    require the .NET Core SDK props files to have been included.
+    Therefore, the following Nullable Reference Type settings are moved to
+    the .targets file instead.
+  -->
+  <!--
+    Extended nullable annotion attributes are available in
+    - .NET Core, Version=3.0 (and later)
+    - .NET Standard, Version=2.1 (and later)
+    
+    Use Conditional ItemGroup to exclude TargetFramework specifications matching
+    the versions listed above.
+  -->
+  <ItemGroup Label="Nullable helper library for Pre-.NET Standard 2.1"
+             Condition="!(
+              ('$(TargetFrameworkIdentifier)' == '.NETCoreApp'  AND '$(_TargetFrameworkVersionWithoutV)' &gt;= '3.0') OR
+              ('$(TargetFrameworkIdentifier)' == '.NETStandard' AND '$(_TargetFrameworkVersionWithoutV)' &gt;= '2.1')
+              )">
+    <PackageReference Include="Nullable" Version="1.2.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+</Project>
\ No newline at end of file
diff --git a/src/Xunit.SkippableFact/Skip.cs b/src/Xunit.SkippableFact/Skip.cs
index d74ab1a..6a32793 100644
--- a/src/Xunit.SkippableFact/Skip.cs
+++ b/src/Xunit.SkippableFact/Skip.cs
@@ -3,9 +3,7 @@
 
 namespace Xunit
 {
-#if NETSTANDARD2_1
     using System.Diagnostics.CodeAnalysis;
-#endif
 
     /// <summary>
     /// Static methods for dynamically skipping tests identified with
@@ -19,9 +17,7 @@ public static class Skip
         /// <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(
-#if NETSTANDARD2_1
             [DoesNotReturnIf(true)]
-#endif
             bool condition,
             string? reason = null)
         {
@@ -37,9 +33,7 @@ public static void If(
         /// <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(
-#if NETSTANDARD2_1
             [DoesNotReturnIf(false)]
-#endif
             bool condition,
             string? reason = null)
         {

From 0bd79690a9e796303d9072595cfa77d638fd8ab6 Mon Sep 17 00:00:00 2001
From: Andrew Arnott <andrewarnott@gmail.com>
Date: Thu, 9 Jul 2020 07:26:21 -0600
Subject: [PATCH 4/4] Simplify build authoring required for nullable
 annotations

---
 Directory.Build.props                         |  1 +
 Directory.Build.targets                       | 27 -------------------
 src/Xunit.SkippableFact/Skip.cs               |  6 ++---
 .../Xunit.SkippableFact.csproj                |  4 +--
 test/Xunit.SkippableFact.Tests/SkipTests.cs   |  4 +--
 .../Xunit.SkippableFact.Tests.csproj          |  2 +-
 6 files changed, 7 insertions(+), 37 deletions(-)
 delete mode 100644 Directory.Build.targets

diff --git a/Directory.Build.props b/Directory.Build.props
index 87fa852..bb79b93 100644
--- a/Directory.Build.props
+++ b/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="$(MSBuildThisFileDirectory)stylecop.json" />
diff --git a/Directory.Build.targets b/Directory.Build.targets
deleted file mode 100644
index 9a8d6c7..0000000
--- a/Directory.Build.targets
+++ /dev/null
@@ -1,27 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project>
-  <!-- 
-    Usage of TargetFrameworkIdentifier and _TargetFrameworkVersionWithoutV
-    require the .NET Core SDK props files to have been included.
-    Therefore, the following Nullable Reference Type settings are moved to
-    the .targets file instead.
-  -->
-  <!--
-    Extended nullable annotion attributes are available in
-    - .NET Core, Version=3.0 (and later)
-    - .NET Standard, Version=2.1 (and later)
-    
-    Use Conditional ItemGroup to exclude TargetFramework specifications matching
-    the versions listed above.
-  -->
-  <ItemGroup Label="Nullable helper library for Pre-.NET Standard 2.1"
-             Condition="!(
-              ('$(TargetFrameworkIdentifier)' == '.NETCoreApp'  AND '$(_TargetFrameworkVersionWithoutV)' &gt;= '3.0') OR
-              ('$(TargetFrameworkIdentifier)' == '.NETStandard' AND '$(_TargetFrameworkVersionWithoutV)' &gt;= '2.1')
-              )">
-    <PackageReference Include="Nullable" Version="1.2.1">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
-    </PackageReference>
-  </ItemGroup>
-</Project>
\ No newline at end of file
diff --git a/src/Xunit.SkippableFact/Skip.cs b/src/Xunit.SkippableFact/Skip.cs
index 6a32793..8c5ec7a 100644
--- a/src/Xunit.SkippableFact/Skip.cs
+++ b/src/Xunit.SkippableFact/Skip.cs
@@ -17,8 +17,7 @@ public static class Skip
         /// <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(
-            [DoesNotReturnIf(true)]
-            bool condition,
+            [DoesNotReturnIf(true)] bool condition,
             string? reason = null)
         {
             if (condition)
@@ -33,8 +32,7 @@ public static void If(
         /// <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(
-            [DoesNotReturnIf(false)]
-            bool condition,
+            [DoesNotReturnIf(false)] bool condition,
             string? reason = null)
         {
             Skip.If(!condition, reason);
diff --git a/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj b/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
index 4ff32fd..b16fd6b 100644
--- a/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
+++ b/src/Xunit.SkippableFact/Xunit.SkippableFact.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;net45;net452</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net45;net452</TargetFrameworks>
     <RootNamespace>Xunit</RootNamespace>
 
     <Title>Dynamic test skipping for Xunit</Title>
@@ -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' " />
diff --git a/test/Xunit.SkippableFact.Tests/SkipTests.cs b/test/Xunit.SkippableFact.Tests/SkipTests.cs
index c8b530d..0ea1ef6 100644
--- a/test/Xunit.SkippableFact.Tests/SkipTests.cs
+++ b/test/Xunit.SkippableFact.Tests/SkipTests.cs
@@ -49,7 +49,6 @@ public void IfNot_WithReason()
             }
         }
 
-#if NETCOREAPP3_1
         [Fact]
         public void If_SupportsNullableReferenceTypesPostCondition()
         {
@@ -76,11 +75,10 @@ public void IfNot_SupportsNullableReferenceTypesPostCondition()
                 ? "Not null"
                 : null;
 
-            Skip.IfNot(!(value is null));
+            Skip.IfNot(value is object);
 
             // Does not trigger a nullable reference type warning
             _ = value.Substring(0);
         }
-#endif
     }
 }
diff --git a/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj b/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
index f7c1072..4193404 100644
--- a/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
+++ b/test/Xunit.SkippableFact.Tests/Xunit.SkippableFact.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net45;net461;netcoreapp2.1;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net45;net461;netcoreapp2.1</TargetFrameworks>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>