Make the EventSource generator incremental et.al.

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Emitter.cs

@@ -12,97 +12,86 @@ namespace Generators
 {
     public partial class EventSourceGenerator
     {
-        private sealed class Emitter
-        {
-            private readonly StringBuilder _builder = new StringBuilder(1024);
-            private readonly GeneratorExecutionContext _context;
-
-            public Emitter(GeneratorExecutionContext context) => _context = context;
-
-            public void Emit(EventSourceClass[] eventSources, CancellationToken cancellationToken)
-            {
-                foreach (EventSourceClass? ec in eventSources)
-                {
-                    if (cancellationToken.IsCancellationRequested)
-                    {
-                        // stop any additional work
-                        break;
-                    }
+        /// <summary>Code for a [GeneratedCode] attribute to put on the top-level generated members.</summary>
+        private static readonly string s_generatedCodeAttribute = $"[global::System.CodeDom.Compiler.GeneratedCodeAttribute(\"{typeof(EventSourceGenerator).Assembly.GetName().Name}\", \"{typeof(EventSourceGenerator).Assembly.GetName().Version}\")]";
 
-                    _builder.AppendLine("using System;");
-                    GenType(ec);
+        private static void EmitSourceFile(SourceProductionContext context, EventSourceClass ec)
+        {
+            StringBuilder sb = new StringBuilder(1024);
 
-                    _context.AddSource($"{ec.ClassName}.g.cs", SourceText.From(_builder.ToString(), Encoding.UTF8));
+            sb.AppendLine(@"// <auto-generated/>");
+            sb.AppendLine();
+            sb.AppendLine("using System;");
+            GenType(ec, sb);
 
-                    _builder.Clear();
-                }
-            }
+            context.AddSource($"{ec.ClassName}.g.cs", SourceText.From(sb.ToString(), Encoding.UTF8));
+        }
 
-            private void GenType(EventSourceClass ec)
+        private static void GenType(EventSourceClass ec, StringBuilder sb)
+        {
+            if (!string.IsNullOrWhiteSpace(ec.Namespace))
             {
-                if (!string.IsNullOrWhiteSpace(ec.Namespace))
-                {
-                    _builder.AppendLine($@"
+                sb.AppendLine($@"
 namespace {ec.Namespace}
 {{");
-                }
+            }
 
-                _builder.AppendLine($@"
+            sb.AppendLine($@"
+    {s_generatedCodeAttribute}
     partial class {ec.ClassName}
     {{");
-                GenerateConstructor(ec);
+            GenerateConstructor(ec, sb);
 
-                GenerateProviderMetadata(ec.SourceName);
+            GenerateProviderMetadata(ec.SourceName, sb);
 
-                _builder.AppendLine($@"
+            sb.AppendLine($@"
     }}");
 
-                if (!string.IsNullOrWhiteSpace(ec.Namespace))
-                {
-                    _builder.AppendLine($@"
+            if (!string.IsNullOrWhiteSpace(ec.Namespace))
+            {
+                sb.AppendLine($@"
 }}");
-                }
             }
+        }
 
-            private void GenerateConstructor(EventSourceClass ec)
-            {
-                _builder.AppendLine($@"
+        private static void GenerateConstructor(EventSourceClass ec, StringBuilder sb)
+        {
+            sb.AppendLine($@"
         private {ec.ClassName}() : base(new Guid({ec.Guid.ToString("x").Replace("{", "").Replace("}", "")}), ""{ec.SourceName}"") {{ }}");
-            }
+        }
 
-            private void GenerateProviderMetadata(string sourceName)
-            {
-                _builder.Append(@"
+        private static void GenerateProviderMetadata(string sourceName, StringBuilder sb)
+        {
+            sb.Append(@"
         private protected override ReadOnlySpan<byte> ProviderMetadata => new byte[] { ");
 
-                byte[] metadataBytes = MetadataForString(sourceName);
-                foreach (byte b in metadataBytes)
-                {
-                    _builder.Append($"0x{b:x}, ");
-                }
-
-                _builder.AppendLine(@"};");
-            }
-
-            // From System.Private.CoreLib
-            private static byte[] MetadataForString(string name)
+            byte[] metadataBytes = MetadataForString(sourceName);
+            foreach (byte b in metadataBytes)
             {
-                CheckName(name);
-                int metadataSize = Encoding.UTF8.GetByteCount(name) + 3;
-                byte[]? metadata = new byte[metadataSize];
-                ushort totalSize = checked((ushort)(metadataSize));
-                metadata[0] = unchecked((byte)totalSize);
-                metadata[1] = unchecked((byte)(totalSize >> 8));
-                Encoding.UTF8.GetBytes(name, 0, name.Length, metadata, 2);
-                return metadata;
+                sb.Append($"0x{b:x}, ");
             }
 
-            private static void CheckName(string? name)
+            sb.AppendLine(@"};");
+        }
+
+        // From System.Private.CoreLib
+        private static byte[] MetadataForString(string name)
+        {
+            CheckName(name);
+            int metadataSize = Encoding.UTF8.GetByteCount(name) + 3;
+            byte[]? metadata = new byte[metadataSize];
+            ushort totalSize = checked((ushort)(metadataSize));
+            metadata[0] = unchecked((byte)totalSize);
+            metadata[1] = unchecked((byte)(totalSize >> 8));
+            Encoding.UTF8.GetBytes(name, 0, name.Length, metadata, 2);
+            return metadata;
+        }
+
+        private static void CheckName(string? name)
+        {
+            if (name != null && 0 <= name.IndexOf('\0'))
             {
-                if (name != null && 0 <= name.IndexOf('\0'))
-                {
-                    throw new ArgumentOutOfRangeException(nameof(name));
-                }
+                throw new ArgumentOutOfRangeException(nameof(name));
             }
         }
     }