Generate warning suppressions in an XML format

docs/error-codes.md

@@ -69,6 +69,10 @@ the error code. For example:
 
 - The value given for the --warn argument was not a valid warning version. Valid versions include integers in the range 0-9999, though not all of these map to distinct warning waves.
 
+#### `IL1017`: Invalid value 'value' for '--generate-warning-suppressions' option
+
+- Invalid value 'value' was used for command-line option '--generate-warning-suppressions'; must be 'cs' or 'xml'.
+
 ----
 ## Warning Codes
 

docs/illink-options.md

@@ -170,12 +170,14 @@ warnings.
 
 ### Generating warning suppressions
 
-For each of the linked assemblies that triggered any warnings during the linking, the
-`--generate-warning-suppressions` option will generate a file containing a list with the
-necessary attributes to suppres these. The attributes contained in this files are
-assembly-level attributes of type `UnconditionalSuppressMessage` specifying the required
-`Scope` and `Target` properties for each of the warnings seen. The generated files are
-saved in the ouput directory and named `<AssemblyName>.WarningSuppressions.cs`.
+For each of the linked assemblies that triggered any warnings during linking, the
+`--generate-warning-suppressions [cs | xml]` option will generate a file containing a list
+with the necessary attributes to suppress these. The generated files can either be C# source
+files or XML files in a [format](data-formats.md#custom-attributes-annotations-format) that is supported by the linker,
+the emitted format depends upon the argument that is passed to this option (`cs` or `xml`.)
+The attributes contained in these files are assembly-level attributes of type `UnconditionalSuppressMessage`
+specifying the required `Scope` and `Target` properties for each of the warnings seen. The
+generated files are saved in the output directory and named `<AssemblyName>.WarningSuppressions.<extension>`.
 
 ## monolinker specific options
 

src/linker/Linker/DocumentationSignatureGenerator.cs

@@ -16,6 +16,12 @@ namespace Mono.Linker
 	/// </summary>
 	public sealed partial class DocumentationSignatureGenerator
 	{
+		internal const string MethodPrefix = "M:";
+		internal const string FieldPrefix = "F:";
+		internal const string EventPrefix = "E:";
+		internal const string PropertyPrefix = "P:";
+		internal const string TypePrefix = "T:";
+
 		public static readonly DocumentationSignatureGenerator Instance = new DocumentationSignatureGenerator ();
 
 		private DocumentationSignatureGenerator ()
@@ -47,31 +53,31 @@ public void VisitMember (IMemberDefinition member, StringBuilder builder)
 
 		private void VisitMethod (MethodDefinition method, StringBuilder builder)
 		{
-			builder.Append ("M:");
+			builder.Append (MethodPrefix);
 			PartVisitor.Instance.VisitMethodDefinition (method, builder);
 		}
 
 		private void VisitField (FieldDefinition field, StringBuilder builder)
 		{
-			builder.Append ("F:");
+			builder.Append (FieldPrefix);
 			PartVisitor.Instance.VisitField (field, builder);
 		}
 
 		private void VisitEvent (EventDefinition evt, StringBuilder builder)
 		{
-			builder.Append ("E:");
+			builder.Append (EventPrefix);
 			PartVisitor.Instance.VisitEvent (evt, builder);
 		}
 
 		private void VisitProperty (PropertyDefinition property, StringBuilder builder)
 		{
-			builder.Append ("P:");
+			builder.Append (PropertyPrefix);
 			PartVisitor.Instance.VisitProperty (property, builder);
 		}
 
 		private void VisitTypeDefinition (TypeDefinition type, StringBuilder builder)
 		{
-			builder.Append ("T:");
+			builder.Append (TypePrefix);
 			PartVisitor.Instance.VisitTypeReference (type, builder);
 		}
 	}

src/linker/Linker/Driver.cs

@@ -426,7 +426,17 @@ protected int SetupContext (ILogger customLogger = null)
 						continue;
 
 					case "--generate-warning-suppressions":
+						string generateWarningSuppressionsArgument = string.Empty;
+						if (!GetStringParam (token, l => generateWarningSuppressionsArgument = l))
+							return -1;
+
+						if (!GetWarningSuppressionWriterFileOutputKind (generateWarningSuppressionsArgument, out var fileOutputKind)) {
+							context.LogError ($"Invalid value '{generateWarningSuppressionsArgument}' for '--generate-warning-suppressions' option", 1017);
+							return -1;
+						}
+
 						context.OutputWarningSuppressions = true;
+						context.SetWarningSuppressionWriter (fileOutputKind);
 						continue;
 
 					case "--nowarn":
@@ -990,6 +1000,23 @@ static bool GetOptimizationName (string text, out CodeOptimizations optimization
 			return false;
 		}
 
+		static bool GetWarningSuppressionWriterFileOutputKind (string text, out WarningSuppressionWriter.FileOutputKind fileOutputKind)
+		{
+			switch (text.ToLowerInvariant ()) {
+			case "cs":
+				fileOutputKind = WarningSuppressionWriter.FileOutputKind.CSharp;
+				return true;
+
+			case "xml":
+				fileOutputKind = WarningSuppressionWriter.FileOutputKind.Xml;
+				return true;
+
+			default:
+				fileOutputKind = WarningSuppressionWriter.FileOutputKind.CSharp;
+				return false;
+			}
+		}
+
 		bool GetBoolParam (string token, Action<bool> action)
 		{
 			if (arguments.Count == 0) {

src/linker/Linker/LinkContext.cs

@@ -172,7 +172,7 @@ public ISymbolWriterProvider SymbolWriterProvider {
 
 		public KnownMembers MarkedKnownMembers { get; private set; }
 
-		public WarningSuppressionWriter WarningSuppressionWriter { get; }
+		public WarningSuppressionWriter WarningSuppressionWriter { get; private set; }
 
 		public HashSet<uint> NoWarn { get; set; }
 
@@ -236,7 +236,6 @@ public LinkContext (Pipeline pipeline, AssemblyResolver resolver, ReaderParamete
 			StripLinkAttributes = true;
 			PInvokes = new List<PInvokeInfo> ();
 			Suppressions = new UnconditionalSuppressMessageAttributeState (this);
-			WarningSuppressionWriter = new WarningSuppressionWriter (this);
 			NoWarn = new HashSet<uint> ();
 			GeneralWarnAsError = false;
 			WarnAsError = new Dictionary<uint, bool> ();
@@ -624,6 +623,11 @@ public static WarnVersion GetWarningVersion (int code)
 			// This should return an increasing WarnVersion for new warning waves.
 			return WarnVersion.ILLink5;
 		}
+
+		public void SetWarningSuppressionWriter (WarningSuppressionWriter.FileOutputKind fileOutputKind)
+		{
+			WarningSuppressionWriter = new WarningSuppressionWriter (this, fileOutputKind);
+		}
 	}
 
 	public class CodeOptimizationsSettings

src/linker/Linker/UnconditionalSuppressMessageAttributeState.cs

@@ -6,6 +6,10 @@ namespace Mono.Linker
 {
 	public class UnconditionalSuppressMessageAttributeState
 	{
+		internal const string ScopeProperty = "Scope";
+		internal const string TargetProperty = "Target";
+		internal const string MessageIdProperty = "MessageId";
+
 		private readonly LinkContext _context;
 		private readonly Dictionary<ICustomAttributeProvider, Dictionary<int, SuppressMessageInfo>> _suppressions;
 		private HashSet<AssemblyDefinition> InitializedAssemblies { get; }
@@ -99,13 +103,13 @@ private static bool TryDecodeSuppressMessageAttributeData (CustomAttribute attri
 			if (attribute.HasProperties) {
 				foreach (var p in attribute.Properties) {
 					switch (p.Name) {
-					case "Scope":
+					case ScopeProperty:
 						info.Scope = (p.Argument.Value as string)?.ToLower ();
 						break;
-					case "Target":
+					case TargetProperty:
 						info.Target = p.Argument.Value as string;
 						break;
-					case "MessageId":
+					case MessageIdProperty:
 						info.MessageId = p.Argument.Value as string;
 						break;
 					}

src/linker/Linker/WarningSuppressionWriter.cs

@@ -2,19 +2,24 @@
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Xml;
+using System.Xml.Linq;
 using Mono.Cecil;
 
 namespace Mono.Linker
 {
 	public class WarningSuppressionWriter
 	{
 		private readonly LinkContext _context;
-		private readonly Dictionary<AssemblyNameDefinition, HashSet<(int, IMemberDefinition)>> _warnings;
+		private readonly Dictionary<AssemblyNameDefinition, HashSet<(int Code, IMemberDefinition Member)>> _warnings;
+		private readonly FileOutputKind _fileOutputKind;
 
-		public WarningSuppressionWriter (LinkContext context)
+		public WarningSuppressionWriter (LinkContext context,
+			FileOutputKind fileOutputKind = FileOutputKind.CSharp)
 		{
 			_context = context;
 			_warnings = new Dictionary<AssemblyNameDefinition, HashSet<(int, IMemberDefinition)>> ();
+			_fileOutputKind = fileOutputKind;
 		}
 
 		public void AddWarning (int code, IMemberDefinition memberDefinition)
@@ -31,46 +36,82 @@ public void AddWarning (int code, IMemberDefinition memberDefinition)
 		public void OutputSuppressions ()
 		{
 			foreach (var assemblyName in _warnings.Keys) {
-				using (var sw = new StreamWriter (Path.Combine (_context.OutputDirectory, $"{assemblyName.Name}.WarningSuppressions.cs"))) {
-					StringBuilder sb = new StringBuilder ("using System.Diagnostics.CodeAnalysis;").AppendLine ().AppendLine ();
-					List<(int Code, IMemberDefinition Member)> listOfWarnings = _warnings[assemblyName].ToList ();
-					listOfWarnings.Sort ((a, b) => {
-						string lhs = a.Member is MethodReference lhsMethod ? lhsMethod.GetDisplayName () : a.Member.FullName;
-						string rhs = b.Member is MethodReference rhsMethod ? rhsMethod.GetDisplayName () : b.Member.FullName;
-						if (lhs == rhs)
-							return a.Code.CompareTo (b.Code);
+				if (_fileOutputKind == FileOutputKind.Xml) {
+					OutputSuppressionsXmlFormat (assemblyName);
+				} else {
+					OutputSuppressionsCSharpFormat (assemblyName);
+				}
+			}
+		}
 
-						return string.CompareOrdinal (lhs, rhs);
-					});
+		void OutputSuppressionsXmlFormat (AssemblyNameDefinition assemblyName)
+		{
+			var xmlTree =
+				new XElement ("linker",
+					new XElement ("assembly", new XAttribute ("fullname", assemblyName.FullName)));
 
-					foreach (var warning in listOfWarnings) {
-						int warningCode = warning.Code;
-						IMemberDefinition warningOrigin = warning.Member;
-						sb.Append ("[assembly: UnconditionalSuppressMessage (\"");
-						sb.Append (Constants.ILLink);
-						sb.Append ("\", \"IL");
-						sb.Append (warningCode).Append ("\", Scope = \"");
-						switch (warningOrigin.MetadataToken.TokenType) {
-						case TokenType.TypeDef:
-							sb.Append ("type\", Target = \"");
-							break;
-						case TokenType.Method:
-						case TokenType.Property:
-						case TokenType.Field:
-						case TokenType.Event:
-							sb.Append ("member\", Target = \"");
-							break;
-						default:
-							break;
-						}
+			foreach (var warning in GetListOfWarnings (assemblyName)) {
+				xmlTree.Element ("assembly").Add (
+					new XElement ("attribute",
+						new XAttribute ("fullname", "System.Diagnostics.CodeAnalysis.UnconditionalSuppressMessageAttribute"),
+						new XElement ("argument", Constants.ILLink),
+						new XElement ("argument", $"IL{warning.Code}"),
+						new XElement ("property", new XAttribute ("name", UnconditionalSuppressMessageAttributeState.ScopeProperty),
+							GetWarningSuppressionScopeString (warning.MemberDocumentationSignature)),
+						new XElement ("property", new XAttribute ("name", UnconditionalSuppressMessageAttributeState.TargetProperty),
+							warning.MemberDocumentationSignature)));
+			}
 
-						DocumentationSignatureGenerator.Instance.VisitMember (warningOrigin, sb);
-						sb.AppendLine ("\")]");
-					}
+			XDocument xdoc = new XDocument (xmlTree);
+			using (var xw = XmlWriter.Create (Path.Combine (_context.OutputDirectory, $"{assemblyName.Name}.WarningSuppressions.xml"),
+				new XmlWriterSettings { Indent = true })) {
+				xdoc.Save (xw);
+			}
+		}
 
-					sw.Write (sb.ToString ());
+		void OutputSuppressionsCSharpFormat (AssemblyNameDefinition assemblyName)
+		{
+			using (var sw = new StreamWriter (Path.Combine (_context.OutputDirectory, $"{assemblyName.Name}.WarningSuppressions.cs"))) {
+				StringBuilder sb = new StringBuilder ("using System.Diagnostics.CodeAnalysis;").AppendLine ().AppendLine ();
+				foreach (var warning in GetListOfWarnings (assemblyName)) {
+					sb.Append ("[assembly: UnconditionalSuppressMessage (\"")
+						.Append (Constants.ILLink)
+						.Append ("\", \"IL").Append (warning.Code)
+						.Append ("\", Scope = \"").Append (GetWarningSuppressionScopeString (warning.MemberDocumentationSignature))
+						.Append ("\", Target = \"").Append (warning.MemberDocumentationSignature)
+						.AppendLine ("\")]");
 				}
+
+				sw.Write (sb.ToString ());
+			}
+		}
+
+		List<(int Code, string MemberDocumentationSignature)> GetListOfWarnings (AssemblyNameDefinition assemblyName)
+		{
+			List<(int Code, string MemberDocumentationSignature)> listOfWarnings = new List<(int Code, string MemberDocumentationSignature)> ();
+			StringBuilder sb = new StringBuilder ();
+			foreach (var warning in _warnings[assemblyName].ToList ()) {
+				DocumentationSignatureGenerator.Instance.VisitMember (warning.Member, sb);
+				listOfWarnings.Add ((warning.Code, sb.ToString ()));
+				sb.Clear ();
 			}
+
+			listOfWarnings.Sort ();
+			return listOfWarnings;
+		}
+
+		static string GetWarningSuppressionScopeString (string memberDocumentationSignature)
+		{
+			if (memberDocumentationSignature.StartsWith (DocumentationSignatureGenerator.TypePrefix))
+				return "type";
+
+			return "member";
 		}
+
+		public enum FileOutputKind
+		{
+			CSharp,
+			Xml
+		};
 	}
 }

test/Mono.Linker.Tests.Cases/Warnings/WarningSuppression/CanGenerateWarningSuppressionFile.cs → test/Mono.Linker.Tests.Cases/Warnings/WarningSuppression/CanGenerateWarningSuppressionFileCSharp.cs

@@ -13,8 +13,8 @@ namespace Mono.Linker.Tests.Cases.Warnings.WarningSuppression
 	[KeptAssembly ("library.dll")]
 	[SetupLinkerAction ("link", "library.dll")]
 	[SetupLinkerArgument ("--verbose")]
-	[SetupLinkerArgument ("--generate-warning-suppressions")]
-	public class CanGenerateWarningSuppressionFile
+	[SetupLinkerArgument ("--generate-warning-suppressions", "cs")]
+	public class CanGenerateWarningSuppressionFileCSharp
 	{
 		public static void Main ()
 		{
@@ -36,7 +36,7 @@ class Warnings
 		[Kept]
 		public static Type TriggerUnrecognizedPattern ()
 		{
-			return typeof (CanGenerateWarningSuppressionFile);
+			return typeof (CanGenerateWarningSuppressionFileCSharp);
 		}
 
 		[Kept]

test/Mono.Linker.Tests.Cases/Warnings/WarningSuppression/CanGenerateWarningSuppressionFileXml.cs

@@ -0,0 +1,24 @@
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Metadata;
+using Mono.Linker.Tests.Cases.Warnings.WarningSuppression.Dependencies;
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Text;
+
+namespace Mono.Linker.Tests.Cases.Warnings.WarningSuppression
+{
+	[SetupLinkerCoreAction ("skip")]
+	[SetupCompileBefore ("library.dll", new[] { "Dependencies/TriggerWarnings_Lib.cs" })]
+	[KeptAssembly ("library.dll")]
+	[SetupLinkerAction ("link", "library.dll")]
+	[SetupLinkerArgument ("--verbose")]
+	[SetupLinkerArgument ("--generate-warning-suppressions", "xml")]
+	public class CanGenerateWarningSuppressionFileXml
+	{
+		public static void Main ()
+		{
+			TriggerWarnings_Lib.Main ();
+		}
+	}
+}