Add new analyzer API (DiagnosticSuppressor) to allow programmatic sup…

src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs

@@ -2686,9 +2686,9 @@ internal override bool CompileMethods(
                     filterOpt: filterOpt,
                     cancellationToken: cancellationToken);
 
-                bool hasMethodBodyErrorOrWarningAsError = !FilterAndAppendAndFreeDiagnostics(diagnostics, ref methodBodyDiagnosticBag);
+                bool hasMethodBodyError = !FilterAndAppendAndFreeDiagnostics(diagnostics, ref methodBodyDiagnosticBag);
 
-                if (hasDeclarationErrors || hasMethodBodyErrorOrWarningAsError)
+                if (hasDeclarationErrors || hasMethodBodyError)
                 {
                     return false;
                 }

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

@@ -2766,7 +2766,7 @@ public void TestSymbolStartAnalyzer_MultipleAnalyzers_NamedTypeAndMethods()
         }
 
         [Fact]
-        private void TestSymbolStartAnalyzer_MultipleAnalyzers_AllSymbolKinds()
+        public void TestSymbolStartAnalyzer_MultipleAnalyzers_AllSymbolKinds()
         {
             testCore("SymbolStartTopLevelRuleId", topLevel: true);
             testCore("SymbolStartRuleId", topLevel: false);

src/Compilers/Core/Portable/CodeAnalysisResources.resx

@@ -419,6 +419,9 @@
   <data name="DiagnosticIdCantBeNullOrWhitespace" xml:space="preserve">
     <value>A DiagnosticDescriptor must have an Id that is neither null nor an empty string nor a string that only contains white space.</value>
   </data>
+  <data name="SuppressionIdCantBeNullOrWhitespace" xml:space="preserve">
+    <value>A SuppressionDescriptor must have an Id that is neither null nor an empty string nor a string that only contains white space.</value>
+  </data>
   <data name="RuleSetHasDuplicateRules" xml:space="preserve">
     <value>The rule set file has duplicate rules for '{0}' with differing actions '{1}' and '{2}'.</value>
   </data>
@@ -443,6 +446,15 @@
   <data name="UnsupportedDiagnosticReported" xml:space="preserve">
     <value>Reported diagnostic with ID '{0}' is not supported by the analyzer.</value>
   </data>
+  <data name="UnsupportedSuppressionReported" xml:space="preserve">
+    <value>Reported suppression with ID '{0}' is not supported by the suppressor.</value>
+  </data>
+  <data name="InvalidDiagnosticSuppressionReported" xml:space="preserve">
+    <value>Suppressed diagnostic ID '{0}' does not match suppressable ID '{1}' for the given suppression descriptor.</value>
+  </data>
+  <data name="NonReportedDiagnosticCannotBeSuppressed" xml:space="preserve">
+    <value>Non-reported diagnostic with ID '{0}' cannot be suppressed.</value>
+  </data>
   <data name="InvalidDiagnosticIdReported" xml:space="preserve">
     <value>Reported diagnostic has an ID '{0}', which is not a valid identifier.</value>
   </data>
@@ -452,6 +464,9 @@
   <data name="SupportedDiagnosticsHasNullDescriptor" xml:space="preserve">
     <value>Analyzer '{0}' contains a null descriptor in its 'SupportedDiagnostics'.</value>
   </data>
+  <data name="SupportedSuppressionsHasNullDescriptor" xml:space="preserve">
+    <value>Analyzer '{0}' contains a null descriptor in its 'SupportedSuppressions'.</value>
+  </data>
   <data name="The_type_0_is_not_understood_by_the_serialization_binder" xml:space="preserve">
     <value>The type '{0}' is not understood by the serialization binder.</value>
   </data>
@@ -645,4 +660,13 @@
   <data name="WRN_InvalidSeverityInAnalyzerConfig_Title" xml:space="preserve">
     <value>Invalid severity in analyzer config file.</value>
   </data>
+  <data name="DiagnosticSuppressorFeatureDisabled" xml:space="preserve">
+    <value>Feature 'DiagnosticSuppressor' is disabled.</value>
+  </data>
+  <data name="SuppressionDiagnosticDescriptorTitle" xml:space="preserve">
+    <value>Programmatic suppression of an analyzer diagnostic</value>
+  </data>
+  <data name="SuppressionDiagnosticDescriptorMessage" xml:space="preserve">
+    <value>Diagnostic '{0}' was programmatically suppressed by a DiagnosticSuppressor with suppresion ID '{1}' and justification '{2}'</value>
+  </data>
 </root>

src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs

@@ -485,6 +485,14 @@ internal bool ReportDiagnostics(IEnumerable<Diagnostic> diagnostics, TextWriter
         {
             bool hasErrors = false;
             foreach (var diag in diagnostics)
+            {
+                reportDiagnostic(diag);
+            }
+
+            return hasErrors;
+
+            // Local functions
+            void reportDiagnostic(Diagnostic diag)
             {
                 if (_reportedDiagnostics.Contains(diag))
                 {
@@ -496,20 +504,38 @@ internal bool ReportDiagnostics(IEnumerable<Diagnostic> diagnostics, TextWriter
                     // we previously created.
                     //this assert isn't valid if we change the design to not bail out after each phase.
                     //System.Diagnostics.Debug.Assert(diag.Severity != DiagnosticSeverity.Error);
-                    continue;
+                    return;
                 }
                 else if (diag.Severity == DiagnosticSeverity.Hidden)
                 {
                     // Not reported from the command-line compiler.
-                    continue;
+                    return;
                 }
 
                 // We want to report diagnostics with source suppression in the error log file.
                 // However, these diagnostics should not be reported on the console output.
                 errorLoggerOpt?.LogDiagnostic(diag);
+
+                // If the diagnostic was suppressed by one or more DiagnosticSuppressor(s), then we report info diagnostics for each suppression
+                // so that the suppression information is available in the binary logs and verbose build logs.
+                if (diag.ProgrammaticSuppressionInfo != null)
+                {
+                    foreach (var (id, justification) in diag.ProgrammaticSuppressionInfo.Suppressions)
+                    {
+                        // Diagnostic '{0}' was programmatically suppressed by a DiagnosticSuppressor with suppresion ID '{1}' and justification '{2}'
+                        var suppressionDiag = Diagnostic.Create(SuppressionDiagnosticDescriptor, diag.Location, diag.Id, id, justification);
+                        if (_reportedDiagnostics.Add(suppressionDiag))
+                        {
+                            PrintError(suppressionDiag, consoleOutput);
+                        }
+                    }
+
+                    return;
+                }
+
                 if (diag.IsSuppressed)
                 {
-                    continue;
+                    return;
                 }
 
                 // Diagnostics that aren't suppressed will be reported to the console output and, if they are errors,
@@ -523,10 +549,16 @@ internal bool ReportDiagnostics(IEnumerable<Diagnostic> diagnostics, TextWriter
 
                 _reportedDiagnostics.Add(diag);
             }
-
-            return hasErrors;
         }
 
+        private readonly DiagnosticDescriptor SuppressionDiagnosticDescriptor = new DiagnosticDescriptor(
+            "SP0001",
+            CodeAnalysisResources.SuppressionDiagnosticDescriptorTitle,
+            CodeAnalysisResources.SuppressionDiagnosticDescriptorMessage,
+            "ProgrammaticSuppression",
+            DiagnosticSeverity.Info,
+            isEnabledByDefault: true);
+
         /// <summary>Returns true if there were any errors, false otherwise.</summary>
         private bool ReportDiagnostics(DiagnosticBag diagnostics, TextWriter consoleOutput, ErrorLogger errorLoggerOpt)
             => ReportDiagnostics(diagnostics.ToReadOnly(), consoleOutput, errorLoggerOpt);
@@ -1022,9 +1054,16 @@ private void CompileAndEmit(
                             // TryComplete, we may miss diagnostics.
                             var hostDiagnostics = analyzerDriver.GetDiagnosticsAsync(compilation).Result;
                             diagnostics.AddRange(hostDiagnostics);
-                            if (hostDiagnostics.Any(IsReportedError))
+
+                            if (!diagnostics.IsEmptyWithoutResolution)
                             {
-                                success = false;
+                                // Apply diagnostic suppressions for analyzer and/or compiler diagnostics from diagnostic suppressors.
+                                analyzerDriver.ApplyProgrammaticSuppressions(diagnostics, compilation);
+
+                                if (diagnostics.AsEnumerable().Any(IsReportedError))
+                                {
+                                    success = false;
+                                }
                             }
                         }
                     }

src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -1379,7 +1379,7 @@ internal bool FilterAndAppendDiagnostics(DiagnosticBag accumulator, IEnumerable<
                     continue;
                 }
                 else if (filtered.Severity == DiagnosticSeverity.Error &&
-                         !filtered.IsSuppressed)
+                    !filtered.IsSuppressed)
                 {
                     hasError = true;
                 }