Port JetBrains' nullability annotations and clean-up code. (#2018)

* Make a helper method specific to .NET Standard 2.0.

* Enable nullable annotations and remove the JetBrains attributes.

* Update packages and use the SDK's analyzers.

* Use newer platform detection APIs when available.

* `IsMacOSX` -> `IsMacOS`

* `IsiOS` -> `IsIOS`

Author: teo-tsirpanis

build/common.props

@@ -16,6 +16,7 @@
     <ComVisible>false</ComVisible>
 
     <UseSharedCompilation>false</UseSharedCompilation>
+    <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <SuppressNETCoreSdkPreviewMessage>True</SuppressNETCoreSdkPreviewMessage>
     <CodeAnalysisRuleSet>$(MSBuildThisFileDirectory)CodingStyle.ruleset</CodeAnalysisRuleSet>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
@@ -57,7 +58,7 @@
     <PackageVersion>$(Major).$(Minor).$(Revision).$(BuildNumber)$(PrereleaseLabel)</PackageVersion>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0">
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
@@ -67,8 +68,5 @@
     <PackageReference Include="StyleCop.Analyzers" Version="1.1.118">
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="2.9.4">
-      <PrivateAssets>all</PrivateAssets>
-    </PackageReference>
   </ItemGroup>
 </Project>

samples/BenchmarkDotNet.Samples/BenchmarkDotNet.Samples.csproj

@@ -14,11 +14,11 @@
   </PropertyGroup>
   <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' ">
     <Reference Include="System.Reflection" />
+    <PackageReference Include="System.Memory" Version="4.5.5" />
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="System.Drawing.Common" Version="4.7.2" />
-    <PackageReference Include="System.Memory" Version="4.5.5" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\BenchmarkDotNet\BenchmarkDotNet.csproj" />

src/BenchmarkDotNet/Analysers/AnalyserBase.cs

@@ -21,11 +21,11 @@ public IEnumerable<Conclusion> Analyse(Summary summary)
         [PublicAPI] protected virtual IEnumerable<Conclusion> AnalyseSummary(Summary summary) => Enumerable.Empty<Conclusion>();
         [PublicAPI] protected virtual IEnumerable<Conclusion> AnalyseReport(BenchmarkReport report, Summary summary) => Enumerable.Empty<Conclusion>();
 
-        protected Conclusion CreateHint(string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        protected Conclusion CreateHint(string message, BenchmarkReport? report = null, bool mergeable = true)
             => Conclusion.CreateHint(Id, message, report, mergeable);
-        protected Conclusion CreateWarning(string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        protected Conclusion CreateWarning(string message, BenchmarkReport? report = null, bool mergeable = true)
             => Conclusion.CreateWarning(Id, message, report, mergeable);
-        protected Conclusion CreateError(string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        protected Conclusion CreateError(string message, BenchmarkReport? report = null, bool mergeable = true)
             => Conclusion.CreateError(Id, message, report, mergeable);
     }
 }

src/BenchmarkDotNet/Analysers/Conclusion.cs

@@ -7,23 +7,20 @@ namespace BenchmarkDotNet.Analysers
     // TODO: Find a better name
     public sealed class Conclusion : IEquatable<Conclusion>
     {
-        [NotNull]
         public string AnalyserId { get; }
 
         public ConclusionKind Kind { get; }
 
         public bool Mergeable { get; }
 
-        [NotNull]
         public string Message { get; }
 
-        [CanBeNull]
-        public BenchmarkReport Report { get; }
+        public BenchmarkReport? Report { get; }
 
-        private Conclusion([NotNull] string analyserId,
+        private Conclusion(string analyserId,
                            ConclusionKind kind,
-                           [NotNull] string message,
-                           [CanBeNull] BenchmarkReport report,
+                           string message,
+                           BenchmarkReport? report,
                            bool mergeable)
         {
             AnalyserId = analyserId;
@@ -33,13 +30,13 @@ private Conclusion([NotNull] string analyserId,
             Mergeable = mergeable;
         }
 
-        public static Conclusion CreateHint(string analyserId, string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        public static Conclusion CreateHint(string analyserId, string message, BenchmarkReport? report = null, bool mergeable = true)
             => new Conclusion(analyserId, ConclusionKind.Hint, message, report, mergeable);
 
-        public static Conclusion CreateWarning(string analyserId, string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        public static Conclusion CreateWarning(string analyserId, string message, BenchmarkReport? report = null, bool mergeable = true)
             => new Conclusion(analyserId, ConclusionKind.Warning, message, report, mergeable);
 
-        public static Conclusion CreateError(string analyserId, string message, [CanBeNull] BenchmarkReport report = null, bool mergeable = true)
+        public static Conclusion CreateError(string analyserId, string message, BenchmarkReport? report = null, bool mergeable = true)
             => new Conclusion(analyserId, ConclusionKind.Error, message, report, mergeable);
 
         public bool Equals(Conclusion other)

src/BenchmarkDotNet/Analysers/MultimodalDistributionAnalyzer.cs

@@ -30,8 +30,7 @@ protected override IEnumerable<Conclusion> AnalyseReport(BenchmarkReport report,
                 yield return Create("can have several modes", mValue, report, summary.GetCultureInfo());
         }
 
-        [NotNull]
-        private Conclusion Create([NotNull] string kind, double mValue, [CanBeNull] BenchmarkReport report, CultureInfo cultureInfo)
+        private Conclusion Create(string kind, double mValue, BenchmarkReport? report, CultureInfo cultureInfo)
             => CreateWarning($"It seems that the distribution {kind} (mValue = {mValue.ToString("0.##", cultureInfo)})", report);
     }
 }

src/BenchmarkDotNet/Analysers/OutliersAnalyser.cs

@@ -55,7 +55,7 @@ protected override IEnumerable<Conclusion> AnalyseReport(BenchmarkReport report,
         /// <param name="upperOutliers">All upper outliers</param>
         /// <param name="cultureInfo">CultureInfo</param>
         /// <returns>The message</returns>
-        [PublicAPI, NotNull, Pure]
+        [PublicAPI, Pure]
         public static string GetMessage(double[] actualOutliers, double[] allOutliers, double[] lowerOutliers, double[] upperOutliers, CultureInfo cultureInfo)
         {
             if (allOutliers.Length == 0)
@@ -80,8 +80,7 @@ string Format(int n, string verb)
             return Format(actualOutliers.Length, "removed") + ", " + Format(allOutliers.Length, "detected") + rangeMessage;
         }
 
-        [CanBeNull]
-        private static string GetRangeMessage([NotNull] double[] values, CultureInfo cultureInfo)
+        private static string? GetRangeMessage(double[] values, CultureInfo cultureInfo)
         {
             string Format(double value) => TimeInterval.FromNanoseconds(value).ToString(cultureInfo, "N2");
 

src/BenchmarkDotNet/BenchmarkDotNet.csproj

@@ -4,6 +4,7 @@
     <AssemblyTitle>BenchmarkDotNet</AssemblyTitle>
     <TargetFrameworks>netstandard2.0;net6.0</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>annotations</Nullable>
     <NoWarn>$(NoWarn);1701;1702;1705;1591;3005;NU1702;CS3001;CS3003</NoWarn>
     <AssemblyName>BenchmarkDotNet</AssemblyName>
     <PackageId>BenchmarkDotNet</PackageId>
@@ -22,16 +23,18 @@
     <PackageReference Include="Microsoft.Diagnostics.Runtime" Version="2.2.332302" />
     <PackageReference Include="Perfolizer" Version="0.2.1" />
     <PackageReference Include="System.Management" Version="6.0.0" />
-    <PackageReference Include="System.Reflection.Emit" Version="4.7.0" />
-    <PackageReference Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
-    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.0.0" />
     <PackageReference Include="Microsoft.Diagnostics.Tracing.TraceEvent" Version="3.0.2" PrivateAssets="contentfiles;analyzers" />
     <PackageReference Include="Microsoft.DotNet.PlatformAbstractions" Version="3.1.6" />
   </ItemGroup>
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETStandard' ">
     <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
+    <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
+  </ItemGroup>
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="System.Reflection.Emit" Version="4.7.0" />
+    <PackageReference Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
   </ItemGroup>
   <ItemGroup Condition="'$(OS)' == 'Windows_NT' AND '$(UseMonoRuntime)' != 'true' ">
     <ProjectReference Include="..\BenchmarkDotNet.Disassembler.x64\BenchmarkDotNet.Disassembler.x64.csproj">
@@ -48,7 +51,7 @@
   <ItemGroup>
     <ProjectReference Include="..\BenchmarkDotNet.Annotations\BenchmarkDotNet.Annotations.csproj" />
   </ItemGroup>
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETStandard' ">
     <Compile Include="..\BenchmarkDotNet.Annotations\Attributes\DynamicallyAccessedMembersAttribute.cs" Link="Properties\DynamicallyAccessedMembersAttribute.cs" />
     <Compile Include="..\BenchmarkDotNet.Annotations\Attributes\DynamicallyAccessedMemberTypes.cs" Link="Properties\DynamicallyAccessedMemberTypes.cs" />
   </ItemGroup>

src/BenchmarkDotNet/Characteristics/CharacteristicObject.cs

@@ -5,8 +5,6 @@
 using System.Reflection;
 using JetBrains.Annotations;
 
-using NotNullAttribute = JetBrains.Annotations.NotNullAttribute;
-
 namespace BenchmarkDotNet.Characteristics
 {
     // TODO: better naming.
@@ -343,8 +341,8 @@ protected CharacteristicObject ApplyCore(CharacteristicObject other) =>
                 GetCharacteristicsToApply(other));
 
         private CharacteristicObject ApplyCore(
-            [CanBeNull] CharacteristicObject other,
-            [NotNull] IEnumerable<Characteristic> characteristicsToApply)
+            CharacteristicObject? other,
+            IEnumerable<Characteristic> characteristicsToApply)
         {
             AssertNotFrozen();
 

src/BenchmarkDotNet/Columns/BaselineAllocationRatioColumn.cs

@@ -63,8 +63,8 @@ private static bool IsNonBaselinesPrecise(Summary summary, IReadOnlyDictionary<s
         }
 
         private static double? GetAllocationRatio(
-            [CanBeNull] IReadOnlyDictionary<string, Metric> current,
-            [CanBeNull] IReadOnlyDictionary<string, Metric> baseline)
+            IReadOnlyDictionary<string, Metric>? current,
+            IReadOnlyDictionary<string, Metric>? baseline)
         {
             double? currentBytes = GetAllocatedBytes(current);
             double? baselineBytes = GetAllocatedBytes(baseline);
@@ -78,7 +78,7 @@ private static bool IsNonBaselinesPrecise(Summary summary, IReadOnlyDictionary<s
             return currentBytes / baselineBytes;
         }
 
-        private static double? GetAllocatedBytes([CanBeNull] IReadOnlyDictionary<string, Metric> metrics)
+        private static double? GetAllocatedBytes(IReadOnlyDictionary<string, Metric>? metrics)
         {
             var metric = metrics?.Values.FirstOrDefault(m => m.Descriptor is AllocatedMemoryMetricDescriptor);
             return metric?.Value;

src/BenchmarkDotNet/Columns/BaselineRatioColumn.cs

@@ -118,8 +118,7 @@ private static bool IsNonBaselinesPrecise(Summary summary, Statistics baselineSt
             return nonBaselines.Any(x => GetRatioStatistics(summary[x].ResultStatistics, baselineStat)?.Mean < 0.01);
         }
 
-        [CanBeNull]
-        private static Statistics GetRatioStatistics([CanBeNull] Statistics current, [CanBeNull] Statistics baseline)
+        private static Statistics? GetRatioStatistics(Statistics? current, Statistics? baseline)
         {
             if (current == null || current.N < 1)
                 return null;