Merge pull request #124 from bkoelman/warning-level

Updated AV2210 to require warning level 9999

Author: bkoelman

docs/Overview.md

@@ -163,7 +163,7 @@ This analyzer reports when:
 
 ### [AV2210](https://github.com/dennisdoomen/CSharpGuidelines/blob/7a66f7468da6ce1477753a02e416e04bc9a44e45/_pages/2200_FrameworkGuidelines.md#av2210): Build with the highest warning level ![](/images/warn.png "severity: warning")
 This analyzer reports when:
-- the compiler warning level is below 4 in the build settings
+- the compiler warning level is below [9999](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-options/errors-warnings#warninglevel) in the build settings
 - warnings are not treated as errors in the build settings.
 
 Note: this analyzer requires [Full Solution Analysis](/docs/Full%20Solution%20Analysis.md) enabled.

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer.Test/Specs/Framework/BuildWithTheHighestWarningLevelSpecs.cs

@@ -10,11 +10,11 @@ public sealed class BuildWithTheHighestWarningLevelSpecs : CSharpGuidelinesAnaly
         protected override string DiagnosticId => BuildWithTheHighestWarningLevelAnalyzer.DiagnosticId;
 
         [Fact]
-        internal void When_warning_level_is_set_to_four_it_must_be_skipped()
+        internal void When_warning_level_is_9999_with_warnings_as_errors_it_must_be_skipped()
         {
             // Arrange
             ParsedSourceCode source = new TypeSourceCodeBuilder()
-                .CompileAtWarningLevel(4)
+                .CompileAtWarningLevel(9999)
                 .CompileWithWarningAsError()
                 .Build();
 
@@ -23,66 +23,25 @@ internal void When_warning_level_is_set_to_four_it_must_be_skipped()
         }
 
         [Fact]
-        internal void When_warning_level_is_set_to_three_it_must_be_reported()
+        internal void When_warning_level_is_below_9999_it_must_be_reported()
         {
             // Arrange
             ParsedSourceCode source = new TypeSourceCodeBuilder()
-                .CompileAtWarningLevel(3)
+                .CompileAtWarningLevel(5)
                 .CompileWithWarningAsError()
                 .Build();
 
             // Act and assert
             VerifyGuidelineDiagnostic(source,
-                "Build with warning level 4.");
+                "Build with warning level 9999.");
         }
 
         [Fact]
-        internal void When_warning_level_is_set_to_two_it_must_be_reported()
-        {
-            // Arrange
-            ParsedSourceCode source = new TypeSourceCodeBuilder()
-                .CompileAtWarningLevel(2)
-                .CompileWithWarningAsError()
-                .Build();
-
-            // Act and assert
-            VerifyGuidelineDiagnostic(source,
-                "Build with warning level 4.");
-        }
-
-        [Fact]
-        internal void When_warning_level_is_set_to_one_it_must_be_reported()
-        {
-            // Arrange
-            ParsedSourceCode source = new TypeSourceCodeBuilder()
-                .CompileAtWarningLevel(1)
-                .CompileWithWarningAsError()
-                .Build();
-
-            // Act and assert
-            VerifyGuidelineDiagnostic(source,
-                "Build with warning level 4.");
-        }
-
-        // Note: at warning level 0, analyzers do not even run. So a test for that is omitted here.
-
-        [Fact]
-        internal void When_compiling_with_warnings_as_errors_it_must_be_skipped()
-        {
-            // Arrange
-            ParsedSourceCode source = new TypeSourceCodeBuilder()
-                .CompileWithWarningAsError()
-                .Build();
-
-            // Act and assert
-            VerifyGuidelineDiagnostic(source);
-        }
-
-        [Fact]
-        internal void When_compiling_with_warnings_not_as_errors_it_must_be_skipped()
+        internal void When_compiling_with_warnings_not_as_errors_it_must_be_reported()
         {
             // Arrange
             ParsedSourceCode source = new TypeSourceCodeBuilder()
+                .CompileAtWarningLevel(9999)
                 .Build();
 
             // Act and assert

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer/Rules/Framework/BuildWithTheHighestWarningLevelAnalyzer.cs

@@ -10,10 +10,14 @@ namespace CSharpGuidelinesAnalyzer.Rules.Framework
     public sealed class BuildWithTheHighestWarningLevelAnalyzer : DiagnosticAnalyzer
     {
         private const string Title = "Compiler warnings are not treated as errors or warning level is too low";
-        private const string WarningLevelMessageFormat = "Build with warning level 4.";
+        private const string WarningLevelMessageFormat = "Build with warning level 9999.";
         private const string WarningAsErrorMessageFormat = "Build with -warnaserror.";
         private const string Description = "Build with the highest warning level.";
 
+        // The highest warning level used to be 4, until C# 9 added warning level 5. Microsoft now recommends to use 9999, which should include all
+        // future warning levels. See https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-options/errors-warnings#warninglevel.
+        private const int MaxWarningLevel = 9999;
+
         public const string DiagnosticId = "AV2210";
 
         [NotNull]
@@ -50,7 +54,7 @@ private static void AnalyzeCompilationOptions(CompilationAnalysisContext context
                 context.ReportDiagnostic(Diagnostic.Create(WarningAsErrorRule, Location.None));
             }
 
-            if (options.WarningLevel < 4)
+            if (options.WarningLevel < MaxWarningLevel)
             {
                 context.ReportDiagnostic(Diagnostic.Create(WarningLevelRule, Location.None));
             }

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer/Rules/Framework/FavorAsyncAwaitOverTaskContinuationAnalyzer.cs

@@ -100,14 +100,15 @@ public TaskTypeInfo([NotNull] Compilation compilation)
                 GenericTaskType = KnownTypes.SystemThreadingTasksTaskT(compilation);
                 TaskType = KnownTypes.SystemThreadingTasksTask(compilation);
 
-                ContinueWithMethodGroup = GetTaskContinueWithMethodGroup();
+                ContinueWithMethodGroup = GetTaskContinueWithMethodGroup(TaskType, GenericTaskType);
             }
 
             [ItemNotNull]
-            private ImmutableArray<ISymbol> GetTaskContinueWithMethodGroup()
+            private static ImmutableArray<ISymbol> GetTaskContinueWithMethodGroup([CanBeNull] INamedTypeSymbol taskType,
+                [CanBeNull] INamedTypeSymbol genericTaskType)
             {
-                ImmutableArray<ISymbol> taskContinueWithMethodGroup = TaskType?.GetMembers("ContinueWith") ?? ImmutableArray<ISymbol>.Empty;
-                ImmutableArray<ISymbol> genericTaskContinueWithMethodGroup = GenericTaskType?.GetMembers("ContinueWith") ?? ImmutableArray<ISymbol>.Empty;
+                ImmutableArray<ISymbol> taskContinueWithMethodGroup = taskType?.GetMembers("ContinueWith") ?? ImmutableArray<ISymbol>.Empty;
+                ImmutableArray<ISymbol> genericTaskContinueWithMethodGroup = genericTaskType?.GetMembers("ContinueWith") ?? ImmutableArray<ISymbol>.Empty;
 
                 return taskContinueWithMethodGroup.Union(genericTaskContinueWithMethodGroup).ToImmutableArray();
             }

src/Directory.Build.props

@@ -2,6 +2,7 @@
 <Project>
   <PropertyGroup>
     <LangVersion>8.0</LangVersion>
+    <WarningLevel>9999</WarningLevel>
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
 
     <!-- Required for code coverage -->