Collect DllImport details through Roslyn semantic model

DllImportGenerator/Ancillary.Interop/Ancillary.Interop.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+    <LangVersion>8.0</LangVersion>
+  </PropertyGroup>
+
+</Project>

DllImportGenerator/Ancillary.Interop/GeneratedDllImportAttribute.cs

@@ -0,0 +1,25 @@
+#nullable enable
+
+namespace System.Runtime.InteropServices
+{
+    // [TODO] Remove once the attribute has been added to the BCL
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+    public sealed class GeneratedDllImportAttribute : Attribute
+    {
+        public bool BestFitMapping;
+        public CallingConvention CallingConvention;
+        public CharSet CharSet;
+        public string? EntryPoint;
+        public bool ExactSpelling;
+        public bool PreserveSig;
+        public bool SetLastError;
+        public bool ThrowOnUnmappableChar;
+
+        public GeneratedDllImportAttribute(string dllName)
+        {
+            this.Value = dllName;
+        }
+
+        public string Value { get; private set; }
+    }
+}

DllImportGenerator/Demo/Demo.csproj

@@ -8,6 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\Ancillary.Interop\Ancillary.Interop.csproj" />
     <ProjectReference Include="..\DllImportGenerator\DllImportGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
   </ItemGroup>
 

DllImportGenerator/DllImportGenerator.Test/CodeSnippets.cs

@@ -153,6 +153,50 @@ partial class Test
     [GeneratedDllImport(""DoesNotExist"", EntryPoint=""UserDefinedEntryPoint"")]
     public static partial void NotAnExport();
 }
+";
+
+        /// <summary>
+        /// Declaration with all DllImport named arguments.
+        /// </summary>
+        public static readonly string AllDllImportNamedArguments = @"
+using System.Runtime.InteropServices;
+partial class Test
+{
+    [GeneratedDllImport(""DoesNotExist"",
+        BestFitMapping = false,
+        CallingConvention = CallingConvention.Cdecl,
+        CharSet = CharSet.Unicode,
+        EntryPoint = ""UserDefinedEntryPoint"",
+        ExactSpelling = true,
+        PreserveSig = false,
+        SetLastError = true,
+        ThrowOnUnmappableChar = true)]
+    public static partial void Method();
+}
+";
+
+        /// <summary>
+        /// Declaration using various methods to compute constants in C#.
+        /// </summary>
+        public static readonly string UseCSharpFeaturesForConstants = @"
+using System.Runtime.InteropServices;
+partial class Test
+{
+    private const bool IsTrue = true;
+    private const bool IsFalse = false;
+    private const string EntryPointName = nameof(Test) + nameof(IsFalse);
+
+    [GeneratedDllImport(nameof(Test),
+        BestFitMapping = 0 != 1,
+        CallingConvention = (CallingConvention)1,
+        CharSet = (CharSet)2,
+        EntryPoint = EntryPointName,
+        ExactSpelling = IsTrue,
+        PreserveSig = IsFalse,
+        SetLastError = !IsFalse,
+        ThrowOnUnmappableChar = !IsTrue)]
+    public static partial void Method();
+}
 ";
 
         /// <summary>
@@ -181,6 +225,52 @@ partial class Test
     [GeneratedDllImport(""DoesNotExist"")]
     public static partial void Method(int t = 0);
 }
+";
+
+        /// <summary>
+        /// Apply MarshalAsAttribute to parameters and return types.
+        /// </summary>
+        public static readonly string MarshalAsAttributeOnTypes = @"
+using System;
+using System.Runtime.InteropServices;
+namespace NS
+{
+    class MyCustomMarshaler : ICustomMarshaler
+    {
+        static ICustomMarshaler GetInstance(string pstrCookie)
+            => new MyCustomMarshaler();
+
+        public void CleanUpManagedData(object ManagedObj)
+            => throw new NotImplementedException();
+
+        public void CleanUpNativeData(IntPtr pNativeData)
+            => throw new NotImplementedException();
+
+        public int GetNativeDataSize()
+            => throw new NotImplementedException();
+
+        public IntPtr MarshalManagedToNative(object ManagedObj)
+            => throw new NotImplementedException();
+
+        public object MarshalNativeToManaged(IntPtr pNativeData)
+            => throw new NotImplementedException();
+    }
+}
+
+partial class Test
+{
+    [GeneratedDllImport(""DoesNotExist"")]
+    [return: MarshalAs(UnmanagedType.LPWStr)]
+    public static partial string Method1([MarshalAs(UnmanagedType.LPStr)]string t);
+
+    [GeneratedDllImport(""DoesNotExist"")]
+    [return: MarshalAs(UnmanagedType.LPWStr)]
+    public static partial string Method2([MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NS.MyCustomMarshaler), MarshalCookie=""COOKIE1"")]string t);
+
+    [GeneratedDllImport(""DoesNotExist"")]
+    [return: MarshalAs(UnmanagedType.LPWStr)]
+    public static partial string Method3([MarshalAs(UnmanagedType.CustomMarshaler, MarshalType = ""NS.MyCustomMarshaler"", MarshalCookie=""COOKIE2"")]string t);
+}
 ";
 
         /// <summary>

DllImportGenerator/DllImportGenerator.Test/Compiles.cs

@@ -14,8 +14,11 @@ public static IEnumerable<object[]> CodeSnippetsToCompile()
             yield return new[] { CodeSnippets.NestedNamespace };
             yield return new[] { CodeSnippets.NestedTypes };
             yield return new[] { CodeSnippets.UserDefinedEntryPoint };
+            yield return new[] { CodeSnippets.AllDllImportNamedArguments };
             yield return new[] { CodeSnippets.BasicParametersAndModifiers };
             yield return new[] { CodeSnippets.DefaultParameters };
+            yield return new[] { CodeSnippets.UseCSharpFeaturesForConstants };
+            yield return new[] { CodeSnippets.MarshalAsAttributeOnTypes };
         }
 
         [Theory]

DllImportGenerator/DllImportGenerator.Test/DllImportGenerator.Test.csproj

@@ -26,6 +26,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\Ancillary.Interop\Ancillary.Interop.csproj" />
     <ProjectReference Include="..\DllImportGenerator\DllImportGenerator.csproj" />
   </ItemGroup>
 

DllImportGenerator/DllImportGenerator.Test/TestUtils.cs

@@ -1,8 +1,10 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.InteropServices;
 using Xunit;
 
 namespace DllImportGenerator.Test
@@ -34,10 +36,26 @@ public static void AssertPreSourceGeneratorCompilation(Compilation comp)
         /// <param name="outputKind">Output type</param>
         /// <returns>The resulting compilation</returns>
         public static Compilation CreateCompilation(string source, OutputKind outputKind = OutputKind.DynamicallyLinkedLibrary)
-            => CSharpCompilation.Create("compilation",
+        {
+            var mdRefs = new List<MetadataReference>();
+
+            // Include the assembly containing the new attribute and all of its references.
+            // [TODO] Remove once the attribute has been added to the BCL
+            var attrAssem = typeof(GeneratedDllImportAttribute).GetTypeInfo().Assembly;
+            mdRefs.Add(MetadataReference.CreateFromFile(attrAssem.Location));
+            foreach (var assemName in attrAssem.GetReferencedAssemblies())
+            {
+                var assemRef = Assembly.Load(assemName);
+                mdRefs.Add(MetadataReference.CreateFromFile(assemRef.Location));
+            }
+
+            // Add a CoreLib reference
+            mdRefs.Add(MetadataReference.CreateFromFile(typeof(Binder).GetTypeInfo().Assembly.Location));
+            return CSharpCompilation.Create("compilation",
                 new[] { CSharpSyntaxTree.ParseText(source, new CSharpParseOptions(LanguageVersion.Preview)) },
-                new[] { MetadataReference.CreateFromFile(typeof(Binder).GetTypeInfo().Assembly.Location) },
+                mdRefs,
                 new CSharpCompilationOptions(outputKind));
+        }
 
         /// <summary>
         /// Run the supplied generators on the compilation.

DllImportGenerator/DllImportGenerator.sln

@@ -7,7 +7,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DllImportGenerator", "DllIm
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DllImportGenerator.Test", "DllImportGenerator.Test\DllImportGenerator.Test.csproj", "{B8CA13C4-F41B-4ABD-A9F3-63A02C53B96E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Demo", "Demo\Demo.csproj", "{E478EE77-E072-4A42-B453-EBFDA7728717}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Demo", "Demo\Demo.csproj", "{E478EE77-E072-4A42-B453-EBFDA7728717}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ancillary.Interop", "Ancillary.Interop\Ancillary.Interop.csproj", "{E59F0B6A-1137-4179-A91D-33464A775DEB}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -27,6 +29,10 @@ Global
 		{E478EE77-E072-4A42-B453-EBFDA7728717}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E478EE77-E072-4A42-B453-EBFDA7728717}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{E478EE77-E072-4A42-B453-EBFDA7728717}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E59F0B6A-1137-4179-A91D-33464A775DEB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E59F0B6A-1137-4179-A91D-33464A775DEB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E59F0B6A-1137-4179-A91D-33464A775DEB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E59F0B6A-1137-4179-A91D-33464A775DEB}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE