From 3c763466352a882b0e23009cc1ed7d1750129508 Mon Sep 17 00:00:00 2001
From: Calum Grant <calum@semmle.com>
Date: Wed, 18 Dec 2019 11:07:38 +0000
Subject: [PATCH] C#: WIP Adding exception handlers. C#: Improve robustness by
 catching and logging exceptions when generating trap IDs.

---
 csharp/extractor/Semmle.Extraction.CIL/Factories.cs |  4 ++--
 csharp/extractor/Semmle.Extraction/Context.cs       | 10 +++++-----
 csharp/extractor/Semmle.Extraction/Entity.cs        | 13 +++++++++++--
 .../extractor/Semmle.Extraction/TrapExtensions.cs   |  6 ++++++
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/csharp/extractor/Semmle.Extraction.CIL/Factories.cs b/csharp/extractor/Semmle.Extraction.CIL/Factories.cs
index 4ef1d1787832..f522521a8456 100644
--- a/csharp/extractor/Semmle.Extraction.CIL/Factories.cs
+++ b/csharp/extractor/Semmle.Extraction.CIL/Factories.cs
@@ -28,7 +28,7 @@ public T Populate<T>(T e) where T : IExtractedEntity
             else
             {
                 e.Label = cx.GetNewLabel();
-                cx.DefineLabel(e, cx.TrapWriter.Writer);
+                cx.DefineLabel(e, cx.TrapWriter.Writer, cx.Extractor);
                 ids.Add(e, e.Label);
                 cx.PopulateLater(() =>
                 {
@@ -76,7 +76,7 @@ public PrimitiveType Create(PrimitiveTypeCode code)
             {
                 e = new PrimitiveType(this, code);
                 e.Label = cx.GetNewLabel();
-                cx.DefineLabel(e, cx.TrapWriter.Writer);
+                cx.DefineLabel(e, cx.TrapWriter.Writer, cx.Extractor);
                 primitiveTypes[(int)code] = e;
             }
 
diff --git a/csharp/extractor/Semmle.Extraction/Context.cs b/csharp/extractor/Semmle.Extraction/Context.cs
index 3474ab0ebae1..93f993818586 100644
--- a/csharp/extractor/Semmle.Extraction/Context.cs
+++ b/csharp/extractor/Semmle.Extraction/Context.cs
@@ -57,19 +57,19 @@ public Entity CreateEntity<Type, Entity>(ICachedEntityFactory<Type, Entity> fact
         // A recursion guard against writing to the trap file whilst writing an id to the trap file.
         bool WritingLabel = false;
 
-        public void DefineLabel(IEntity entity, TextWriter trapFile)
+        public void DefineLabel(IEntity entity, TextWriter trapFile, IExtractor extractor)
         {
             if (WritingLabel)
             {
                 // Don't define a label whilst writing a label.
-                PopulateLater(() => DefineLabel(entity, trapFile));
+                PopulateLater(() => DefineLabel(entity, trapFile, extractor));
             }
             else
             {
                 try
                 {
                     WritingLabel = true;
-                    entity.DefineLabel(trapFile);
+                    entity.DefineLabel(trapFile, extractor);
                 }
                 finally
                 {
@@ -102,7 +102,7 @@ public Entity CreateEntity2<Type, Entity>(ICachedEntityFactory<Type, Entity> fac
                     entity.Label = label;
                     entityLabelCache[entity] = label;
 
-                    DefineLabel(entity, TrapWriter.Writer);
+                    DefineLabel(entity, TrapWriter.Writer, Extractor);
 
                     if (entity.NeedsPopulation)
                         Populate(init as ISymbol, entity);
@@ -148,7 +148,7 @@ private Entity CreateNonNullEntity<Type, Entity>(ICachedEntityFactory<Type, Enti
 
                 objectEntityCache[init] = entity;
 
-                DefineLabel(entity, TrapWriter.Writer);
+                DefineLabel(entity, TrapWriter.Writer, Extractor);
                 if (entity.NeedsPopulation)
                     Populate(init as ISymbol, entity);
 
diff --git a/csharp/extractor/Semmle.Extraction/Entity.cs b/csharp/extractor/Semmle.Extraction/Entity.cs
index 00b59a0a53fa..0d499ffb7652 100644
--- a/csharp/extractor/Semmle.Extraction/Entity.cs
+++ b/csharp/extractor/Semmle.Extraction/Entity.cs
@@ -1,4 +1,5 @@
 using Microsoft.CodeAnalysis;
+using System;
 using System.IO;
 
 namespace Semmle.Extraction
@@ -141,11 +142,19 @@ public static Entity CreateEntity<Type, Entity>(this ICachedEntityFactory<Type,
         public static Entity CreateEntity2<Type, Entity>(this ICachedEntityFactory<Type, Entity> factory, Context cx, Type init)
             where Entity : ICachedEntity => cx.CreateEntity2(factory, init);
 
-        public static void DefineLabel(this IEntity entity, TextWriter trapFile)
+        public static void DefineLabel(this IEntity entity, TextWriter trapFile, IExtractor extractor)
         {
             trapFile.WriteLabel(entity);
             trapFile.Write("=");
-            entity.WriteQuotedId(trapFile);
+            try
+            {
+                entity.WriteQuotedId(trapFile);
+            }
+            catch(Exception ex)  // lgtm[cs/catch-of-all-exceptions]
+            {
+                trapFile.WriteLine("\"");
+                extractor.Message(new Message("Unhandled exception generating id", entity.ToString(), null, ex.StackTrace.ToString()));
+            }
             trapFile.WriteLine();
         }
 
diff --git a/csharp/extractor/Semmle.Extraction/TrapExtensions.cs b/csharp/extractor/Semmle.Extraction/TrapExtensions.cs
index f3e672b13bb8..de40ef0ae821 100644
--- a/csharp/extractor/Semmle.Extraction/TrapExtensions.cs
+++ b/csharp/extractor/Semmle.Extraction/TrapExtensions.cs
@@ -19,6 +19,12 @@ public static void WriteLabel(this TextWriter trapFile, IEntity entity)
 
         public static void WriteSubId(this TextWriter trapFile, IEntity entity)
         {
+            if (entity is null)
+            {
+                trapFile.Write("<null>");
+                return;
+            }
+
             trapFile.Write('{');
             trapFile.WriteLabel(entity);
             trapFile.Write('}');