Do not apply analyzer bulk configuration to compiler diagnostics

src/Compilers/CSharp/Test/Semantic/Diagnostics/GetDiagnosticsTests.cs

@@ -3,7 +3,9 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -458,5 +460,50 @@ void M()
             analyzerDiagnostics.Verify(expected);
             Assert.False(analyzerDiagnostics.Single().IsSuppressed);
         }
+
+        [Fact]
+        [WorkItem(42116, "https://github.com/dotnet/roslyn/issues/42116")]
+        public async Task TestAnalyzerConfigurationDoesNotAffectCompilerDiagnostics()
+        {
+            var source = @"
+class C
+{
+    void M()
+    {
+        // warning CS0168:  The variable 'x' is declared but never used.
+        int x;
+    }
+}
+";
+            // Verify CS0168 reported from 'Compilation.GetDiagnostics'
+            var compilation = CreateCompilation(source);
+            var compilerDiagnostics = compilation.GetDiagnostics();
+            verifyDiagnostics(compilerDiagnostics);
+
+            // Verify CS0168 reported from 'CSharpCompilerDiagnosticAnalyzer', i.e. the diagnostic analyzer used in the IDE layer to report live compiler diagnostics.
+            var analyzers = ImmutableArray.Create<DiagnosticAnalyzer>(new CSharpCompilerDiagnosticAnalyzer());
+            var compilationWithAnalyzers = compilation.WithAnalyzers(analyzers, new AnalyzerOptions(ImmutableArray<AdditionalText>.Empty));
+            var analyzerDiagnostics = await compilationWithAnalyzers.GetAnalyzerDiagnosticsAsync();
+            verifyDiagnostics(analyzerDiagnostics);
+
+            // Verify CS0168 reported by CSharpCompilerDiagnosticAnalyzer is not affected by "dotnet_analyzer_diagnostic = none"
+            var analyzerConfigOptions = new CompilerAnalyzerConfigOptions(ImmutableDictionary<string, string>.Empty.Add("dotnet_analyzer_diagnostic.severity", "none"));
+            var analyzerConfigOptionsProvider = new CompilerAnalyzerConfigOptionsProvider(
+                ImmutableDictionary<object, AnalyzerConfigOptions>.Empty.Add(compilation.SyntaxTrees.Single(), analyzerConfigOptions));
+            var analyzerOptions = new AnalyzerOptions(ImmutableArray<AdditionalText>.Empty, analyzerConfigOptionsProvider);
+            compilationWithAnalyzers = compilation.WithAnalyzers(analyzers, analyzerOptions);
+            analyzerDiagnostics = await compilationWithAnalyzers.GetAnalyzerDiagnosticsAsync();
+            verifyDiagnostics(analyzerDiagnostics);
+
+            static void verifyDiagnostics(ImmutableArray<Diagnostic> diagnostics)
+            {
+                var expected = Diagnostic(ErrorCode.WRN_UnreferencedVar, "x").WithArguments("x").WithLocation(7, 13);
+                diagnostics.Verify(expected);
+
+                var diagnostic = diagnostics.Single();
+                Assert.Equal(DiagnosticSeverity.Warning, diagnostic.Severity);
+                Assert.False(diagnostic.IsSuppressed);
+            }
+        }
     }
 }

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs

@@ -1679,9 +1679,9 @@ private static Diagnostic GetFilteredDiagnostic(Diagnostic diagnostic, Compilati
         {
             diagnostic = compilation.Options.FilterDiagnostic(diagnostic);
 
-            // Apply bulk configuration from analyzer options, if applicable.
+            // Apply bulk configuration from analyzer options for analyzer diagnostics, if applicable.
             var tree = diagnostic?.Location.SourceTree;
-            if (tree == null || analyzerOptions == null)
+            if (tree == null || analyzerOptions == null || diagnostic.CustomTags.Contains(WellKnownDiagnosticTags.Compiler))
             {
                 return diagnostic;
             }