CSToVBConversion: Allow compile errors to show up when flag toggled

Author: GrahamTheCoder

ICSharpCode.CodeConverter/CSharp/VBToCSConversion.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using ICSharpCode.CodeConverter.Shared;
 using ICSharpCode.CodeConverter.Util;
@@ -29,22 +28,11 @@ public VBToCSConversion()
 
         private CSharpCompilation CreateCompilation(List<SyntaxTree> csTrees)
         {
-            var references = _sourceCompilation.References.Select(ConvertReference);
+            var references = _sourceCompilation.References.Select(ReferenceConverter.ConvertReference);
             return CSharpCompilation.Create("Conversion", csTrees, references,
                 new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
         }
 
-        private MetadataReference ConvertReference(MetadataReference nonLanguageSpecificRef)
-        {
-            if (!(nonLanguageSpecificRef is CompilationReference cr)) return nonLanguageSpecificRef;
-
-            using (var stream = new MemoryStream())
-            {
-                cr.Compilation.Emit(stream);
-                return MetadataReference.CreateFromStream(stream);
-            }
-        }
-
         public SyntaxTree SingleFirstPass(Compilation sourceCompilation, SyntaxTree tree)
         {
             _sourceCompilation = sourceCompilation;

ICSharpCode.CodeConverter/Util/ReferenceConverter.cs

@@ -0,0 +1,19 @@
+using System.IO;
+using Microsoft.CodeAnalysis;
+
+namespace ICSharpCode.CodeConverter.Util
+{
+    public class ReferenceConverter
+    {
+        public static MetadataReference ConvertReference(MetadataReference nonLanguageSpecificRef)
+        {
+            if (!(nonLanguageSpecificRef is CompilationReference cr)) return nonLanguageSpecificRef;
+
+            using (var stream = new MemoryStream())
+            {
+                cr.Compilation.Emit(stream);
+                return MetadataReference.CreateFromStream(stream);
+            }
+        }
+    }
+}

ICSharpCode.CodeConverter/VB/CSToVBConversion.cs

@@ -1,24 +1,40 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using ICSharpCode.CodeConverter.CSharp;
 using ICSharpCode.CodeConverter.Shared;
 using ICSharpCode.CodeConverter.Util;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Text;
+using Microsoft.CodeAnalysis.VisualBasic;
 using VBSyntaxFactory = Microsoft.CodeAnalysis.VisualBasic.SyntaxFactory;
 using CSSyntaxFactory = Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 using CSSyntax = Microsoft.CodeAnalysis.CSharp.Syntax;
+using SyntaxKind = Microsoft.CodeAnalysis.CSharp.SyntaxKind;
 using VBSyntax = Microsoft.CodeAnalysis.VisualBasic.Syntax;
 
 namespace ICSharpCode.CodeConverter.VB
 {
     public class CSToVBConversion : ILanguageConversion
     {
+        private readonly List<SyntaxTree> _firstPassResults = new List<SyntaxTree>();
+        private Compilation _sourceCompilation;
+
+        private VisualBasicCompilation CreateCompilation(List<SyntaxTree> vbTrees)
+        {
+            var references = _sourceCompilation.References.Select(ReferenceConverter.ConvertReference);
+            return VisualBasicCompilation.Create("Conversion", vbTrees, references,
+                new VisualBasicCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+        }
+
         public SyntaxTree SingleFirstPass(Compilation sourceCompilation, SyntaxTree tree)
         {
+            _sourceCompilation = sourceCompilation;
             var converted = CSharpConverter.ConvertCompilationTree((CSharpCompilation)sourceCompilation, (CSharpSyntaxTree)tree);
             var convertedTree = VBSyntaxFactory.SyntaxTree(converted);
+            _firstPassResults.Add(convertedTree);
             return convertedTree;
         }
 
@@ -99,7 +115,18 @@ public SyntaxNode SingleSecondPass(KeyValuePair<string, SyntaxTree> cs)
 
         public string GetWarningsOrNull()
         {
-            return null;
+            var finalCompilation = CreateCompilation(_firstPassResults);
+            var targetErrors = GetDiagnostics(finalCompilation);
+            return targetErrors.Any() ? $"{targetErrors.Count} resulting compilation errors:{Environment.NewLine}{string.Join(Environment.NewLine, targetErrors)}" : null;
+        }
+
+        private static List<string> GetDiagnostics(Compilation compilation)
+        {
+            var diagnostics = compilation.GetDiagnostics()
+                .Where(d => d.Severity == DiagnosticSeverity.Error)
+                .Select(d => $"{d.Id}: {d.GetMessage()}")
+                .ToList();
+            return diagnostics;
         }
 
         public SyntaxTree CreateTree(string text)