C#: Extract unique locations.

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

@@ -72,15 +72,14 @@ public static Assembly CreateOutputAssembly(Context cx)
 
         public override void WriteId(EscapingTextWriter trapFile)
         {
-            if (isOutputAssembly && Context.ExtractionContext.IsStandalone)
+            if (Context.ExtractionContext.IsStandalone)
             {
-                trapFile.Write("buildlessOutputAssembly");
-            }
-            else
-            {
-                trapFile.Write(assembly.ToString());
+                WriteStarId(trapFile);
+                return;
             }
 
+            trapFile.Write(assembly.ToString());
+
             if (assemblyPath is not null)
             {
                 trapFile.Write("#file:///");

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

@@ -29,7 +29,10 @@ public override void Populate(TextWriter trapFile)
             ContainingType!.PopulateGenerics();
 
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
-            trapFile.constructor_location(this, Location);
+            if (Context.ExtractLocation(Symbol))
+            {
+                trapFile.constructor_location(this, Location);
+            }
 
             if (MakeSynthetic)
             {

csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/EmptyLocation.cs

@@ -0,0 +1,58 @@
+using System.IO;
+using System.Threading;
+
+namespace Semmle.Extraction.CSharp.Entities
+{
+    public class EmptyLocation : SourceLocation
+    {
+        private readonly File generatedFile;
+
+        // The Ql library assumes the presence of a single "empty" location.
+        private static EmptyLocation? instance;
+        private static readonly Lock instanceLock = new();
+
+        private EmptyLocation(Context cx)
+            : base(cx, null)
+        {
+            generatedFile = GeneratedFile.Create(cx);
+        }
+
+        public override void Populate(TextWriter trapFile)
+        {
+            trapFile.locations_default(this, generatedFile, 0, 0, 0, 0);
+        }
+
+        public override void WriteId(EscapingTextWriter trapFile)
+        {
+            if (Context.ExtractionContext.IsStandalone)
+            {
+                WriteStarId(trapFile);
+                return;
+            }
+
+            trapFile.Write("loc,");
+            trapFile.WriteSubId(generatedFile);
+            trapFile.Write(",0,0,0,0");
+        }
+
+        public override int GetHashCode() => 98732567;
+
+        public override bool Equals(object? obj) => obj is not null && obj.GetType() == typeof(EmptyLocation);
+
+        public static EmptyLocation Create(Context cx)
+        {
+            lock (instanceLock)
+            {
+                instance ??= EmptyLocationFactory.Instance.CreateEntity(cx, typeof(EmptyLocation), null);
+                return instance;
+            }
+        }
+
+        private class EmptyLocationFactory : CachedEntityFactory<string?, EmptyLocation>
+        {
+            public static EmptyLocationFactory Instance { get; } = new EmptyLocationFactory();
+
+            public override EmptyLocation Create(Context cx, string? init) => new EmptyLocation(cx);
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/Location.cs

@@ -5,7 +5,24 @@ public abstract class Location : CachedEntity<Microsoft.CodeAnalysis.Location?>
     {
 #nullable restore warnings
         protected Location(Context cx, Microsoft.CodeAnalysis.Location? init)
-            : base(cx, init) { }
+            : base(cx, init)
+        { }
+
+        protected static void WriteStarId(EscapingTextWriter writer)
+        {
+            writer.Write('*');
+        }
+
+        public sealed override void WriteQuotedId(EscapingTextWriter writer)
+        {
+            if (Context.ExtractionContext.IsStandalone)
+            {
+                WriteStarId(writer);
+                return;
+            }
+
+            base.WriteQuotedId(writer);
+        }
 
         public override Microsoft.CodeAnalysis.Location? ReportingLocation => Symbol;
 

csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/NonGeneratedSourceLocation.cs

@@ -42,6 +42,12 @@ public File FileEntity
 
         public override void WriteId(EscapingTextWriter trapFile)
         {
+            if (Context.ExtractionContext.IsStandalone)
+            {
+                WriteStarId(trapFile);
+                return;
+            }
+
             trapFile.Write("loc,");
             trapFile.WriteSubId(FileEntity);
             trapFile.Write(',');

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

@@ -43,8 +43,11 @@ public override void Populate(TextWriter trapFile)
                 }
             }
 
-            foreach (var l in Locations)
-                trapFile.method_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                foreach (var l in Locations)
+                    trapFile.method_location(this, l);
+            }
 
             PopulateGenerics(trapFile);
             Overrides(trapFile);

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

@@ -247,7 +247,7 @@ public override void Populate(TextWriter trapFile)
             var typeKey = VarargsType.Create(Context);
             // !! Maybe originaldefinition is wrong
             trapFile.@params(this, "", typeKey, Ordinal, Kind.None, Parent!, this);
-            trapFile.param_location(this, GeneratedLocation.Create(Context));
+            trapFile.param_location(this, EmptyLocation.Create(Context));
         }
 
         protected override int Ordinal => ((Method)Parent!).OriginalDefinition.Symbol.Parameters.Length;

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Analyser.cs

@@ -238,6 +238,9 @@ private void DoAnalyseCompilation()
 
                 compilationEntity = Entities.Compilation.Create(cx);
 
+                // Ensure that the empty location is always created.
+                Entities.EmptyLocation.Create(cx);
+
                 ExtractionContext.CompilationInfos.ForEach(ci => trapWriter.Writer.compilation_info(compilationEntity, ci.key, ci.value));
 
                 ReportProgressTaskDone(currentTaskId, assemblyPath, trapWriter.TrapFile, stopwatch.Elapsed, AnalysisAction.Extracted);

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Context.cs

@@ -550,6 +550,10 @@ public bool Defines(ISymbol symbol) =>
             !SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) ||
             scope.InScope(symbol);
 
+        public bool ExtractLocation(ISymbol symbol) =>
+            SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) &&
+            scope.InScope(symbol);
+
         /// <summary>
         /// Runs the given action <paramref name="a"/>, guarding for trap duplication
         /// based on key <paramref name="key"/>.
@@ -582,14 +586,14 @@ public void WithDuplicationGuard(Key key, Action a)
         public Entities.Location CreateLocation()
         {
             return SourceTree is null
-                ? Entities.GeneratedLocation.Create(this)
+                ? Entities.EmptyLocation.Create(this)
                 : CreateLocation(Microsoft.CodeAnalysis.Location.Create(SourceTree, Microsoft.CodeAnalysis.Text.TextSpan.FromBounds(0, 0)));
         }
 
         public Entities.Location CreateLocation(Microsoft.CodeAnalysis.Location? location)
         {
             return (location is null || location.Kind == LocationKind.None)
-                ? Entities.GeneratedLocation.Create(this)
+                ? Entities.EmptyLocation.Create(this)
                 : location.IsInSource
                     ? Entities.NonGeneratedSourceLocation.Create(this, location)
                     : Entities.Assembly.Create(this, location);

csharp/ql/lib/semmle/code/csharp/Callable.qll

@@ -265,7 +265,7 @@ class Method extends Callable, Virtualizable, Attributable, @method {
     result = Virtualizable.super.getAnUltimateImplementor()
   }
 
-  override Location getALocation() { method_location(this, result) }
+  override Location getALocation() { method_location(this.getUnboundDeclaration(), result) }
 
   /** Holds if this method is an extension method. */
   predicate isExtensionMethod() { this.getParameter(0).hasExtensionMethodModifier() }

csharp/ql/test/library-tests/locations/A.cs

@@ -0,0 +1,18 @@
+using System;
+
+public abstract class A<T>
+{
+    public void Apply(T t) { }
+    public abstract object ToObject(T t);
+}
+
+public class A2 : A<string>
+{
+    public override object ToObject(string t) => t;
+
+    public void M()
+    {
+        A2 other = new();
+        other.Apply("");
+    }
+}

csharp/ql/test/library-tests/locations/B.cs

@@ -0,0 +1,6 @@
+using System;
+
+public class B : A<int>
+{
+    public override object ToObject(int t) => t;
+}

csharp/ql/test/library-tests/locations/C.cs

@@ -0,0 +1,12 @@
+using System;
+
+class C
+{
+    public void M()
+    {
+        B b = new B();
+        b.Apply(0);
+        A2 a2 = new A2();
+        a2.Apply("");
+    }
+}

csharp/ql/test/library-tests/locations/locations.expected

@@ -0,0 +1,10 @@
+| A.cs:3:23:3:26 | A<Int32> | A.cs:5:17:5:21 | Apply | A.cs:5:17:5:21 | A.cs:5:17:5:21 |
+| A.cs:3:23:3:26 | A<Int32> | A.cs:6:28:6:35 | ToObject | A.cs:6:28:6:35 | A.cs:6:28:6:35 |
+| A.cs:3:23:3:26 | A<String> | A.cs:5:17:5:21 | Apply | A.cs:5:17:5:21 | A.cs:5:17:5:21 |
+| A.cs:3:23:3:26 | A<String> | A.cs:6:28:6:35 | ToObject | A.cs:6:28:6:35 | A.cs:6:28:6:35 |
+| A.cs:3:23:3:26 | A`1 | A.cs:5:17:5:21 | Apply | A.cs:5:17:5:21 | A.cs:5:17:5:21 |
+| A.cs:3:23:3:26 | A`1 | A.cs:6:28:6:35 | ToObject | A.cs:6:28:6:35 | A.cs:6:28:6:35 |
+| A.cs:9:14:9:15 | A2 | A.cs:11:28:11:35 | ToObject | A.cs:11:28:11:35 | A.cs:11:28:11:35 |
+| A.cs:9:14:9:15 | A2 | A.cs:13:17:13:17 | M | A.cs:13:17:13:17 | A.cs:13:17:13:17 |
+| B.cs:3:14:3:14 | B | B.cs:5:28:5:35 | ToObject | B.cs:5:28:5:35 | B.cs:5:28:5:35 |
+| C.cs:3:7:3:7 | C | C.cs:5:17:5:17 | M | C.cs:5:17:5:17 | C.cs:5:17:5:17 |

csharp/ql/test/library-tests/locations/locations.ql

@@ -0,0 +1,5 @@
+import csharp
+
+from Type t, Method m, SourceLocation l
+where t = m.getDeclaringType() and l = m.getLocation() and not l instanceof EmptyLocation
+select t, m, l

csharp/ql/test/library-tests/locations/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone