C#: Fix global statement extraction by extracting statements inside the implicit main method context

csharp/extractor/Semmle.Extraction.CSharp/Entities/ImplicitMainMethod.cs

@@ -0,0 +1,36 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Semmle.Extraction.CSharp.Entities.Statements;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Semmle.Extraction.CSharp.Entities
+{
+    internal class ImplicitMainMethod : OrdinaryMethod
+    {
+        private readonly List<GlobalStatementSyntax> globalStatements;
+
+        public ImplicitMainMethod(Context cx, IMethodSymbol symbol, List<GlobalStatementSyntax> globalStatements)
+            : base(cx, symbol)
+        {
+            this.globalStatements = globalStatements;
+        }
+
+        protected override void PopulateMethodBody(TextWriter trapFile)
+        {
+            GlobalStatementsBlock.Create(Context, this, globalStatements);
+        }
+
+        public static ImplicitMainMethod Create(Context cx, IMethodSymbol method, List<GlobalStatementSyntax> globalStatements)
+        {
+            return ImplicitMainMethodFactory.Instance.CreateEntity(cx, method, (method, globalStatements));
+        }
+
+        private class ImplicitMainMethodFactory : CachedEntityFactory<(IMethodSymbol, List<GlobalStatementSyntax>), ImplicitMainMethod>
+        {
+            public static ImplicitMainMethodFactory Instance { get; } = new ImplicitMainMethodFactory();
+
+            public override ImplicitMainMethod Create(Context cx, (IMethodSymbol, List<GlobalStatementSyntax>) init) => new ImplicitMainMethod(cx, init.Item1, init.Item2);
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Entities/Method.cs

@@ -46,7 +46,7 @@ namespace Semmle.Extraction.CSharp.Entities
             // so there's nothing to extract.
         }
 
-        private void PopulateMethodBody(TextWriter trapFile)
+        protected virtual void PopulateMethodBody(TextWriter trapFile)
         {
             if (!IsSourceDeclaration)
                 return;

csharp/extractor/Semmle.Extraction.CSharp/Entities/OrdinaryMethod.cs

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal class OrdinaryMethod : Method
     {
-        private OrdinaryMethod(Context cx, IMethodSymbol init)
+        protected OrdinaryMethod(Context cx, IMethodSymbol init)
             : base(cx, init) { }
 
         public override string Name => Symbol.GetName();

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/GlobalStatementsBlock.cs

@@ -2,17 +2,22 @@ using Semmle.Extraction.Kinds;
 using System.Linq;
 using System.IO;
 using Semmle.Extraction.Entities;
+using System.Collections.Generic;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System;
 
 namespace Semmle.Extraction.CSharp.Entities.Statements
 {
     internal class GlobalStatementsBlock : Statement
     {
         private readonly Method parent;
+        private readonly List<GlobalStatementSyntax> globalStatements;
 
-        private GlobalStatementsBlock(Context cx, Method parent)
+        private GlobalStatementsBlock(Context cx, Method parent, List<GlobalStatementSyntax> globalStatements)
             : base(cx, StmtKind.BLOCK, parent, 0)
         {
             this.parent = parent;
+            this.globalStatements = globalStatements;
         }
 
         public override Microsoft.CodeAnalysis.Location? ReportingLocation
@@ -27,9 +32,9 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             }
         }
 
-        public static GlobalStatementsBlock Create(Context cx, Method parent)
+        public static GlobalStatementsBlock Create(Context cx, Method parent, List<GlobalStatementSyntax> globalStatements)
         {
-            var ret = new GlobalStatementsBlock(cx, parent);
+            var ret = new GlobalStatementsBlock(cx, parent, globalStatements);
             ret.TryPopulate();
             return ret;
         }
@@ -37,6 +42,14 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
         protected override void PopulateStatement(TextWriter trapFile)
         {
             trapFile.stmt_location(this, Context.CreateLocation(ReportingLocation));
+
+            for (var i = 0; i < globalStatements.Count; i++)
+            {
+                if (globalStatements[i].Statement is not null)
+                {
+                    Statement.Create(Context, globalStatements[i].Statement, this, i);
+                }
+            }
         }
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Populators/CompilationUnitVisitor.cs

@@ -3,7 +3,6 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Semmle.Util.Logging;
 using Semmle.Extraction.CSharp.Entities;
-using Semmle.Extraction.CSharp.Entities.Statements;
 using System.Linq;
 
 namespace Semmle.Extraction.CSharp.Populators
@@ -60,23 +59,14 @@ namespace Semmle.Extraction.CSharp.Populators
             }
 
             var entryPoint = Cx.Compilation.GetEntryPoint(System.Threading.CancellationToken.None);
-            var entryMethod = Method.Create(Cx, entryPoint);
-            if (entryMethod is null)
+            if (entryPoint is null)
             {
                 Cx.ExtractionError("No entry method found. Skipping the extraction of global statements.",
                     null, Cx.CreateLocation(globalStatements[0].GetLocation()), null, Severity.Info);
                 return;
             }
 
-            var block = GlobalStatementsBlock.Create(Cx, entryMethod);
-
-            for (var i = 0; i < globalStatements.Count; i++)
-            {
-                if (globalStatements[i].Statement is not null)
-                {
-                    Statement.Create(Cx, globalStatements[i].Statement, block, i);
-                }
-            }
+            ImplicitMainMethod.Create(Cx, entryPoint, globalStatements);
         }
     }
 }

csharp/ql/test/library-tests/csharp9-standalone/ExtractorError.expected

@@ -1 +0,0 @@
-| GlobalStmt.cs:13:6:13:6 | TagStack unexpectedly empty | Unexpected C# extractor error: TagStack unexpectedly empty\n |