Improve generated code detection to look for <auto-generated> comments at top of file

Source/CSharpEssentials.Tests/GetterOnlyAutoProperty/UseGetterOnlyAutoPropertyAnalyzerTests.cs

@@ -385,5 +385,22 @@ public void NotAvailableInGeneratedCode6()
         {
             VerifyNotAvailableInGeneratedCode("TestDocument.AssemblyAttributes.cs");
         }
+
+        [Test]
+        public void NotAvailableAutoGeneratedCode()
+        {
+            const string code = @"
+// <auto-generated>
+class C
+{
+    public bool MyProperty { get; private set; }
+    public C(bool f)
+    {
+        MyProperty = f;
+    }
+}";
+
+            NoDiagnostic(code, DiagnosticIds.UseGetterOnlyAutoProperty);
+        }
     }
 }

Source/CSharpEssentials.Tests/UseExpressionBodiedMember/UseExpressionBodiedMemberAnalyzerTests.cs

@@ -80,5 +80,21 @@ public void NotAvailableInGeneratedCode6()
         {
             VerifyNotAvailableInGeneratedCode("TestDocument.AssemblyAttributes.cs");
         }
+
+        [Test]
+        public void NotAvailableAutoGeneratedCode()
+        {
+            const string code = @"
+// <auto-generated>
+class C
+{
+    int Property
+    {
+        get { return 42; }
+    }
+}";
+
+            NoDiagnostic(code, DiagnosticIds.UseExpressionBodiedMember);
+        }
     }
 }

Source/CSharpEssentials.Tests/UseNameOf/UseNameOfAnalyzerTests.cs

@@ -165,5 +165,22 @@ public void NotAvailableInGeneratedCode6()
         {
             VerifyNotAvailableInGeneratedCode("TestDocument.AssemblyAttributes.cs");
         }
+
+        [Test]
+        public void NotAvailableAutoGeneratedCode()
+        {
+            const string code = @"
+// <auto-generated>
+using System;
+class C
+{
+    void M(int x)
+    {
+        throw new ArgumentNullException(""x"");
+    }
+}";
+
+            NoDiagnostic(code, DiagnosticIds.UseNameOf);
+        }
     }
 }

Source/CSharpEssentials/Extensions.cs

@@ -1,10 +1,10 @@
 using System;
 using System.Collections.Immutable;
 using System.IO;
+using System.Threading;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Diagnostics;
 
 namespace CSharpEssentials
 {
@@ -58,12 +58,12 @@ public static ArgumentInfo GetArgumentInfo(this SemanticModel semanticModel, Arg
         {
             if (semanticModel == null)
             {
-                throw new ArgumentNullException("semanticModel");
+                throw new ArgumentNullException(nameof(semanticModel));
             }
 
             if (argument == null)
             {
-                throw new ArgumentNullException("argument");
+                throw new ArgumentNullException(nameof(argument));
             }
 
             var argumentList = argument.Parent as ArgumentListSyntax;
@@ -136,7 +136,7 @@ public static ArgumentInfo GetArgumentInfo(this SemanticModel semanticModel, Arg
             return default(ArgumentInfo);
         }
 
-        private static bool IsGeneratedCode(string filePath)
+        private static bool IsGeneratedCodeFile(string filePath)
         {
             if (string.IsNullOrEmpty(filePath))
             {
@@ -168,9 +168,62 @@ private static bool IsGeneratedCode(string filePath)
             return false;
         }
 
-        public static bool IsGeneratedCode(this SyntaxTree tree)
+        private static bool BeginsWithAutoGeneratedComment(SyntaxTree tree, CancellationToken cancellationToken)
         {
-            return IsGeneratedCode(tree.FilePath);
+            var root = tree.GetRoot(cancellationToken);
+            if (root.Kind() == SyntaxKind.CompilationUnit &&
+                root.HasLeadingTrivia)
+            {
+                var leadingTrivia = root.GetLeadingTrivia();
+
+                foreach (var trivia in leadingTrivia)
+                {
+                    if (trivia.Kind() != SyntaxKind.SingleLineCommentTrivia)
+                    {
+                        continue;
+                    }
+
+                    var text = trivia.ToString();
+
+                    // Should start with single-line comment slashes. If not, move along.
+                    if (text.Length < 2 || text[0] != '/' || text[1] != '/')
+                    {
+                        continue;
+                    }
+
+                    // Scan past whitespace.
+                    int index = 2;
+                    while (index < text.Length && char.IsWhiteSpace(text[index]))
+                    {
+                        index++;
+                    }
+
+                    // Check to see if the text of the comment starts with "<auto-generated>".
+                    const string AutoGenerated = "<auto-generated>";
+
+                    if (string.Compare(text, index, AutoGenerated, 0, AutoGenerated.Length, StringComparison.OrdinalIgnoreCase) == 0)
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
+
+        public static bool IsGeneratedCode(this SyntaxTree tree, CancellationToken cancellationToken)
+        {
+            if (IsGeneratedCodeFile(tree.FilePath))
+            {
+                return true;
+            }
+
+            if (BeginsWithAutoGeneratedComment(tree, cancellationToken))
+            {
+                return true;
+            }
+
+            return false;
         }
     }
 }

Source/CSharpEssentials/GetterOnlyAutoProperty/UseGetterOnlyAutoPropertyAnalyzer.cs

@@ -203,7 +203,7 @@ private static Diagnostic CreateDiagnostic(ISymbol symbol, CancellationToken can
                 var property = (PropertyDeclarationSyntax)reference.GetSyntax(cancellationToken);
 
                 // If the property declaration is in generated code, we shouldn't create the diagnostic.
-                if (!property.SyntaxTree.IsGeneratedCode())
+                if (!property.SyntaxTree.IsGeneratedCode(cancellationToken))
                 {
                     var setter = property.AccessorList.Accessors.FirstOrDefault(a => a.IsKind(SyntaxKind.SetAccessorDeclaration));
                     if (setter != null)

Source/CSharpEssentials/UseExpressionBodiedMember/UseExpressionBodiedMemberAnalyzer.cs

@@ -23,7 +23,7 @@ public override void Initialize(AnalysisContext context)
 
         private static void HandleMethodDeclaration(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }
@@ -49,7 +49,7 @@ private static void HandleMethodDeclaration(SyntaxNodeAnalysisContext context)
 
         private void HandleOperatorDeclaration(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }
@@ -70,7 +70,7 @@ private void HandleOperatorDeclaration(SyntaxNodeAnalysisContext context)
 
         private void HandleConversionOperatorDeclaration(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }
@@ -91,7 +91,7 @@ private void HandleConversionOperatorDeclaration(SyntaxNodeAnalysisContext conte
 
         private static void HandlePropertyDeclaration(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }
@@ -112,7 +112,7 @@ private static void HandlePropertyDeclaration(SyntaxNodeAnalysisContext context)
 
         private void HandleIndexerDeclaration(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }

Source/CSharpEssentials/UseNameOf/UseNameOfAnalyzer.cs

@@ -22,7 +22,7 @@ public override void Initialize(AnalysisContext context)
 
         private static void AnalyzeArgument(SyntaxNodeAnalysisContext context)
         {
-            if (context.Node.SyntaxTree.IsGeneratedCode())
+            if (context.Node.SyntaxTree.IsGeneratedCode(context.CancellationToken))
             {
                 return;
             }