Add initial code for diagnostic messages

csharp/extractor/Semmle.Util/Semmle.Util.csproj

@@ -15,6 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Mono.Posix.NETStandard" Version="1.0.0" />
+		<PackageReference Include="Newtonsoft.Json" Version="13.0.2" />
   </ItemGroup>
 
 </Project>

csharp/extractor/Semmle.Util/ToolStatusPage.cs

@@ -0,0 +1,189 @@
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Serialization;
+
+namespace Semmle.Util
+{
+    /// <summary>
+    /// Represents diagnostic messages for the tool status page.
+    /// </summary>
+    public class DiagnosticMessage
+    {
+        /// <summary>
+        /// Represents sources of diagnostic messages.
+        /// </summary>
+        public class TspSource
+        {
+            /// <summary>
+            /// An identifier under which it makes sense to group this diagnostic message.
+            /// This is used to build the SARIF reporting descriptor object.
+            /// </summary>
+            public string Id { get; }
+            /// <summary>
+            /// Display name for the ID. This is used to build the SARIF reporting descriptor object.
+            /// </summary>
+            public string Name { get; }
+            /// <summary>
+            /// Name of the CodeQL extractor. This is used to identify which tool component the reporting descriptor object should be nested under in SARIF.
+            /// </summary>
+            public string? ExtractorName { get; set; }
+
+            public TspSource(string id, string name)
+            {
+                Id = id;
+                Name = name;
+            }
+        }
+
+        /// <summary>
+        /// Enumerates severity levels for diagnostics.
+        /// </summary>
+        [JsonConverter(typeof(StringEnumConverter), typeof(CamelCaseNamingStrategy))]
+        public enum TspSeverity
+        {
+            Note,
+            Warning,
+            Error
+        }
+
+        public class TspVisibility
+        {
+            /// <summary>
+            /// True if the message should be displayed on the status page (defaults to false).
+            /// </summary>
+            public bool? StatusPage { get; set; }
+            /// <summary>
+            /// True if the message should be counted in the diagnostics summary table printed by
+            /// <c>codeql database analyze</c> (defaults to false).
+            /// </summary>
+            public bool? CLISummaryTable { get; set; }
+            /// <summary>
+            /// True if the message should be sent to telemetry (defaults to false).
+            /// </summary>
+            public bool? Telemetry { get; set; }
+        }
+
+        public class TspLocation
+        {
+            /// <summary>
+            /// Path to the affected file if appropriate, relative to the source root.
+            /// </summary>
+            public string? File { get; set; }
+            public int? StartLine { get; set; }
+            public int? StartColumn { get; set; }
+            public int? EndLine { get; set; }
+            public int? EndColumn { get; set; }
+        }
+
+        /// <summary>
+        /// ISO 8601 timestamp.
+        /// </summary>
+        public string Timestamp { get; set; }
+        /// <summary>
+        /// The source of the diagnostic message.
+        /// </summary>
+        public TspSource Source { get; set; }
+        /// <summary>
+        /// GitHub flavored Markdown formatted message. Should include inline links to any help pages.
+        /// </summary>
+        public string? MarkdownMessage { get; set; }
+        /// <summary>
+        /// Plain text message. Used by components where the string processing needed to support
+        /// Markdown is cumbersome.
+        /// </summary>
+        public string? PlaintextMessage { get; set; }
+        /// <summary>
+        /// List of help links intended to supplement <see cref="PlaintextMessage" />.
+        /// </summary>
+        public List<string> HelpLinks { get; }
+        /// <summary>
+        /// SARIF severity.
+        /// </summary>
+        public TspSeverity? Severity { get; set; }
+        /// <summary>
+        /// If true, then this message won't be presented to users.
+        /// </summary>
+        public bool Internal { get; set; }
+        /// <summary>
+        ///
+        /// </summary>
+        public TspVisibility Visibility { get; }
+        public TspLocation Location { get; }
+        /// <summary>
+        /// Structured metadata about the diagnostic message.
+        /// </summary>
+        public Dictionary<string, object> Attributes { get; }
+
+        public DiagnosticMessage(TspSource source)
+        {
+            Timestamp = DateTime.UtcNow.ToString("o", CultureInfo.InvariantCulture);
+            Source = source;
+            HelpLinks = new List<string>();
+            Visibility = new TspVisibility();
+            Location = new TspLocation();
+            Attributes = new Dictionary<string, object>();
+        }
+    }
+
+    /// <summary>
+    /// A wrapper around an underlying <see cref="StreamWriter" /> which allows
+    /// <see cref="DiagnosticMessage" /> objects to be serialized to it.
+    /// </summary>
+    public sealed class DiagnosticsStream : IDisposable
+    {
+        private readonly JsonSerializer serializer;
+        private readonly StreamWriter writer;
+
+        /// <summary>
+        /// Initialises a new <see cref="DiagnosticsStream" /> for a file at <paramref name="path" />.
+        /// </summary>
+        /// <param name="path">The path to the file that should be created.</param>
+        /// <returns>
+        /// A <see cref="DiagnosticsStream" /> object which allows diagnostics to be
+        /// written to a file at <paramname name="path" />.
+        /// </returns>
+        public static DiagnosticsStream ForFile(string path)
+        {
+            var stream = File.CreateText(path);
+            return new DiagnosticsStream(stream);
+        }
+
+        public DiagnosticsStream(StreamWriter streamWriter)
+        {
+            var contractResolver = new DefaultContractResolver
+            {
+                NamingStrategy = new CamelCaseNamingStrategy()
+            };
+
+            serializer = new JsonSerializer
+            {
+                ContractResolver = contractResolver
+            };
+
+            writer = streamWriter;
+        }
+
+        /// <summary>
+        /// Adds <paramref name="message" /> as a new diagnostics entry.
+        /// </summary>
+        /// <param name="message">The diagnostics entry to add.</param>
+        public void AddEntry(DiagnosticMessage message)
+        {
+            serializer.Serialize(writer, message);
+            writer.Flush();
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="DiagnosticsStream" /> object.
+        /// </summary>
+        public void Dispose()
+        {
+            writer.Dispose();
+        }
+    }
+}