From 55893991b6f487b17c33995db3591dda9367a0ee Mon Sep 17 00:00:00 2001
From: Mark Lechtermann <mark.lechtermann@gmail.com>
Date: Fri, 19 Apr 2024 17:55:40 +0200
Subject: [PATCH] fix: Added DispID offset in case of ComVisible false methods
 (#246)

* fix: Added DispID offset in case of ComVisible false methods or properties

* fix: Convert CRLF to LF
---
 src/dscom.test/tests/MemIdTest.cs   | 8 ++++++++
 src/dscom/DispatchIdCreator.cs      | 2 +-
 src/dscom/writer/InterfaceWriter.cs | 9 +++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/dscom.test/tests/MemIdTest.cs b/src/dscom.test/tests/MemIdTest.cs
index 06e3350..2534d2f 100644
--- a/src/dscom.test/tests/MemIdTest.cs
+++ b/src/dscom.test/tests/MemIdTest.cs
@@ -460,6 +460,7 @@ public void IDispatchInterfaceWith3MethodsAndOneComVisibleFalse_MemIdAndVTableSi
         using var method1 = testInterface!.GetFuncDescByName("Method1");
         method1.Should().NotBeNull();
         method1!.Value.oVft.Should().Be(0);
+        method1!.Value.memid.Should().Be((int)Constants.BASE_OLEAUT_DISPID);
 
         using var method2 = testInterface!.GetFuncDescByName("Method2");
         method2.Should().BeNull();
@@ -467,6 +468,7 @@ public void IDispatchInterfaceWith3MethodsAndOneComVisibleFalse_MemIdAndVTableSi
         using var method3 = testInterface!.GetFuncDescByName("Method3");
         method3.Should().NotBeNull();
         method3!.Value.oVft.Should().Be(0);
+        method3!.Value.memid.Should().Be(((int)Constants.BASE_OLEAUT_DISPID) + 2);
     }
 
     [Fact]
@@ -491,6 +493,7 @@ public void IDispatchInterfaceWith3PropertiesAndOneComVisibleFalse_MemIdAndVTabl
         using var method1 = testInterface!.GetFuncDescByName("Property1");
         method1.Should().NotBeNull();
         method1!.Value.oVft.Should().Be(0);
+        method1!.Value.memid.Should().Be((int)Constants.BASE_OLEAUT_DISPID);
 
         using var method2 = testInterface!.GetFuncDescByName("Property2");
         method2.Should().BeNull();
@@ -498,6 +501,7 @@ public void IDispatchInterfaceWith3PropertiesAndOneComVisibleFalse_MemIdAndVTabl
         using var method3 = testInterface!.GetFuncDescByName("Property3", INVOKEKIND.INVOKE_PROPERTYGET);
         method3.Should().NotBeNull();
         method3!.Value.oVft.Should().Be(0);
+        method3!.Value.memid.Should().Be(((int)Constants.BASE_OLEAUT_DISPID) + 4);
     }
 
     [Fact]
@@ -522,6 +526,7 @@ public void DualInterfaceWith3MethodsAndOneComVisibleFalse_MemIdAndVTableSizeAre
         using var method1 = testInterface!.GetFuncDescByName("Method1");
         method1.Should().NotBeNull();
         method1!.Value.oVft.Should().Be(56);
+        method1!.Value.memid.Should().Be((int)Constants.BASE_OLEAUT_DISPID);
 
         using var method2 = testInterface!.GetFuncDescByName("Method2");
         method2.Should().BeNull();
@@ -529,6 +534,7 @@ public void DualInterfaceWith3MethodsAndOneComVisibleFalse_MemIdAndVTableSizeAre
         using var method3 = testInterface!.GetFuncDescByName("Method3");
         method3.Should().NotBeNull();
         method3!.Value.oVft.Should().Be(72);
+        method3!.Value.memid.Should().Be(((int)Constants.BASE_OLEAUT_DISPID) + 2);
     }
 
     [Fact]
@@ -553,6 +559,7 @@ public void DualInterfaceWith3PropertiesAndOneComVisibleFalse_MemIdAndVTableSize
         using var method1 = testInterface!.GetFuncDescByName("Property1");
         method1.Should().NotBeNull();
         method1!.Value.oVft.Should().Be(56);
+        method1!.Value.memid.Should().Be((int)Constants.BASE_OLEAUT_DISPID);
 
         using var method2 = testInterface!.GetFuncDescByName("Property2");
         method2.Should().BeNull();
@@ -560,6 +567,7 @@ public void DualInterfaceWith3PropertiesAndOneComVisibleFalse_MemIdAndVTableSize
         using var method3 = testInterface!.GetFuncDescByName("Property3", INVOKEKIND.INVOKE_PROPERTYGET);
         method3.Should().NotBeNull();
         method3!.Value.oVft.Should().Be(88);
+        method3!.Value.memid.Should().Be(((int)Constants.BASE_OLEAUT_DISPID) + 4);
     }
 
     [Theory]
diff --git a/src/dscom/DispatchIdCreator.cs b/src/dscom/DispatchIdCreator.cs
index aebbc9a..db04a1f 100644
--- a/src/dscom/DispatchIdCreator.cs
+++ b/src/dscom/DispatchIdCreator.cs
@@ -80,7 +80,7 @@ private void AddDispatchId(uint idGenerated, uint? idFromAttribute, MemberInfo m
         }
     }
 
-    private uint GetNextFreeDispId()
+    internal uint GetNextFreeDispId()
     {
         var dispId = _currentDispId;
         _currentDispId++;
diff --git a/src/dscom/writer/InterfaceWriter.cs b/src/dscom/writer/InterfaceWriter.cs
index e9fc371..19865fa 100644
--- a/src/dscom/writer/InterfaceWriter.cs
+++ b/src/dscom/writer/InterfaceWriter.cs
@@ -126,6 +126,7 @@ private void CreateMethodWriters()
         var functionIndex = 0;
         foreach (var methodWriter in MethodWriters)
         {
+            // A methodWriter can be null if ComVisible is false
             if (methodWriter is not null)
             {
                 methodWriter.FunctionIndex = functionIndex;
@@ -133,6 +134,14 @@ private void CreateMethodWriters()
                 DispatchIdCreator!.RegisterMember(methodWriter);
                 functionIndex += methodWriter.IsValid ? 1 : 0;
             }
+            else
+            {
+                // In case of ComVisible false, we need to increment the the next free DispId
+                // This offset is needed to keep the DispId in sync with the VTable and the behavior of tlbexp.
+                DispatchIdCreator!.GetNextFreeDispId();
+            }
+
+            // Increment the index for the VTableOffset
             index++;
         }
     }