Enable overriding of TPA assemblies

4 files changed, 31 insertions, 41 deletions

diff --git a/src/binder/assemblybinder.cpp b/src/binder/assemblybinder.cpp
index a1982ebb37..517eac99d6 100644
--- a/src/binder/assemblybinder.cpp
+++ b/src/binder/assemblybinder.cpp
@@ -50,7 +50,9 @@ BOOL IsCompilationProcess();
 #include "clrprivbindercoreclr.h"
 #include "clrprivbinderassemblyloadcontext.h"
 // Helper function in the VM, invoked by the Binder, to invoke the host assembly resolver
-extern HRESULT RuntimeInvokeHostAssemblyResolver(INT_PTR pManagedAssemblyLoadContextToBindWithin, IAssemblyName *pIAssemblyName, ICLRPrivAssembly **ppLoadedAssembly);
+extern HRESULT RuntimeInvokeHostAssemblyResolver(INT_PTR pManagedAssemblyLoadContextToBindWithin, 
+                                                IAssemblyName *pIAssemblyName, CLRPrivBinderCoreCLR *pTPABinder,
+                                                BINDER_SPACE::AssemblyName *pAssemblyName, ICLRPrivAssembly **ppLoadedAssembly);
 
 // Helper to check if we have a host assembly resolver set
 extern BOOL RuntimeCanUseAppPathAssemblyResolver(DWORD adid);
@@ -1814,6 +1816,7 @@ namespace BINDER_SPACE
 HRESULT AssemblyBinder::BindUsingHostAssemblyResolver (/* in */ INT_PTR pManagedAssemblyLoadContextToBindWithin,
                                                        /* in */ AssemblyName       *pAssemblyName,
                                                       /* in */ IAssemblyName      *pIAssemblyName,
+                                                      /* in */ CLRPrivBinderCoreCLR *pTPABinder,
                                                       /* out */ Assembly           **ppAssembly)
 {
     HRESULT hr = E_FAIL;
@@ -1821,9 +1824,10 @@ HRESULT AssemblyBinder::BindUsingHostAssemblyResolver (/* in */ INT_PTR pManaged
     
     _ASSERTE(pManagedAssemblyLoadContextToBindWithin != NULL);
     
-    // Call into the VM to use the HostAssemblyResolver and load the assembly
+    // RuntimeInvokeHostAssemblyResolver will perform steps 2-4 of CLRPrivBinderAssemblyLoadContext::BindAssemblyByName.
     ICLRPrivAssembly *pLoadedAssembly = NULL;
-    hr = RuntimeInvokeHostAssemblyResolver(pManagedAssemblyLoadContextToBindWithin, pIAssemblyName, &pLoadedAssembly);
+    hr = RuntimeInvokeHostAssemblyResolver(pManagedAssemblyLoadContextToBindWithin, pIAssemblyName, 
+                                           pTPABinder, pAssemblyName, &pLoadedAssembly);
     if (SUCCEEDED(hr))
     {
         _ASSERTE(pLoadedAssembly != NULL);
diff --git a/src/binder/clrprivbinderassemblyloadcontext.cpp b/src/binder/clrprivbinderassemblyloadcontext.cpp
index 57f4ee72c4..8f3a3eef49 100644
--- a/src/binder/clrprivbinderassemblyloadcontext.cpp
+++ b/src/binder/clrprivbinderassemblyloadcontext.cpp
@@ -61,14 +61,19 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindAssemblyByName(IAssemblyName     *
         SAFE_NEW(pAssemblyName, AssemblyName);
         IF_FAIL_GO(pAssemblyName->Init(pIAssemblyName));
         
-        // Check if the assembly is in the TPA list or not. Don't search app paths when using the TPA binder because the actual
-        // binder is using a host assembly resolver.
-        hr = m_pTPABinder->BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly, true /* excludeAppPaths */);
-        if (hr == HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND))
+        // When LoadContext needs to resolve an assembly reference, it will go through the following lookup order:
+        //
+        // 1) Lookup the assembly within the LoadContext itself. If assembly is found, use it.
+        // 2) Invoke the LoadContext's Load method implementation. If assembly is found, use it.
+        // 3) Lookup the assembly within TPABinder. If assembly is found, use it.
+        // 4) Invoke the LoadContext's Resolving event. If assembly is found, use it.
+        // 5) Raise exception.
+        //
+        // This approach enables a LoadContext to override assemblies that have been loaded in TPA context by loading
+        // a different (or even the same!) version.
+        
         {
-            // If we could not find the assembly in the TPA list,
-            // then bind to it in the context of the current binder.
-            // If we find it already loaded, we will return the reference.
+            // Step 1 - Try to find the assembly within the LoadContext.
             hr = BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly);
             if ((hr == HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND)) ||
                 (hr == FUSION_E_APP_DOMAIN_LOCKED) || (hr == FUSION_E_REF_DEF_MISMATCH))
@@ -82,7 +87,8 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindAssemblyByName(IAssemblyName     *
                 // Thus, if default binder has been overridden, then invoke it in an attempt to perform the binding for it make the call
                 // of what to do next. The host-overridden binder can either fail the bind or return reference to an existing assembly
                 // that has been loaded.
-                hr = AssemblyBinder::BindUsingHostAssemblyResolver(GetManagedAssemblyLoadContext(), pAssemblyName, pIAssemblyName, &pCoreCLRFoundAssembly);
+                //
+                hr = AssemblyBinder::BindUsingHostAssemblyResolver(GetManagedAssemblyLoadContext(), pAssemblyName, pIAssemblyName, m_pTPABinder, &pCoreCLRFoundAssembly);
                 if (SUCCEEDED(hr))
                 {
                     // We maybe returned an assembly that was bound to a different AssemblyLoadContext instance.
@@ -142,41 +148,19 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindUsingPEImage( /* in */ PEImage *pP
             IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_BAD_FORMAT));
         }
         
-        // Ensure we are not being asked to bind to a TPA assembly
-        //
-        // Easy out for mscorlib
+        // Disallow attempt to bind to the core library. Aside from that,
+        // the LoadContext can load any assembly (even if it was in a different LoadContext like TPA).
         if (pAssemblyName->IsMscorlib())
         {
             IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND));
         }
 
+        hr = AssemblyBinder::BindUsingPEImage(&m_appContext, pAssemblyName, pPEImage, PeKind, pIMetaDataAssemblyImport, &pCoreCLRFoundAssembly);
+        if (hr == S_OK)
         {
-            SString& simpleName = pAssemblyName->GetSimpleName();
-            ApplicationContext *pTPAApplicationContext = m_pTPABinder->GetAppContext();
-            SimpleNameToFileNameMap * tpaMap = pTPAApplicationContext->GetTpaList();
-            if (tpaMap->LookupPtr(simpleName.GetUnicode()) != NULL)
-            {
-                // The simple name of the assembly being requested to be bound was found in the TPA list.
-                // Now, perform the actual bind to see if the assembly was really in the TPA assembly or not.
-                // Don't search app paths when using the TPA binder because the actual binder is using a host assembly resolver.
-                hr = m_pTPABinder->BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly, true /* excludeAppPaths */);
-                if (SUCCEEDED(hr))
-                {
-                    if (pCoreCLRFoundAssembly->GetIsInGAC())
-                    {
-                        // If we were able to bind to a TPA assembly, then fail the load
-                        IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND));
-                    }
-                }
-            }
-            
-            hr = AssemblyBinder::BindUsingPEImage(&m_appContext, pAssemblyName, pPEImage, PeKind, pIMetaDataAssemblyImport, &pCoreCLRFoundAssembly);
-            if (hr == S_OK)
-            {
-                _ASSERTE(pCoreCLRFoundAssembly != NULL);
-                pCoreCLRFoundAssembly->SetBinder(this);
-                *ppAssembly = pCoreCLRFoundAssembly.Extract();
-            }
+            _ASSERTE(pCoreCLRFoundAssembly != NULL);
+            pCoreCLRFoundAssembly->SetBinder(this);
+            *ppAssembly = pCoreCLRFoundAssembly.Extract();
         }
 Exit:;        
     }
diff --git a/src/binder/clrprivbindercoreclr.cpp b/src/binder/clrprivbindercoreclr.cpp
index a2fb1c8237..d62af867ef 100644
--- a/src/binder/clrprivbindercoreclr.cpp
+++ b/src/binder/clrprivbindercoreclr.cpp
@@ -80,7 +80,8 @@ HRESULT CLRPrivBinderCoreCLR::BindAssemblyByName(IAssemblyName     *pIAssemblyNa
             INT_PTR pManagedAssemblyLoadContext = GetManagedAssemblyLoadContext();
             if (pManagedAssemblyLoadContext != NULL)
             {
-              hr = AssemblyBinder::BindUsingHostAssemblyResolver(pManagedAssemblyLoadContext, pAssemblyName, pIAssemblyName, &pCoreCLRFoundAssembly);
+              hr = AssemblyBinder::BindUsingHostAssemblyResolver(pManagedAssemblyLoadContext, pAssemblyName, pIAssemblyName, 
+              NULL, &pCoreCLRFoundAssembly);
               if (SUCCEEDED(hr))
               {
                   // We maybe returned an assembly that was bound to a different AssemblyLoadContext instance.
diff --git a/src/binder/inc/assemblybinder.hpp b/src/binder/inc/assemblybinder.hpp
index 87d6491a92..3a1f1e45fd 100644
--- a/src/binder/inc/assemblybinder.hpp
+++ b/src/binder/inc/assemblybinder.hpp
@@ -78,6 +78,7 @@ namespace BINDER_SPACE
         static HRESULT BindUsingHostAssemblyResolver (/* in */ INT_PTR pManagedAssemblyLoadContextToBindWithin,
                                                       /* in */ AssemblyName       *pAssemblyName,
                                                       /* in */ IAssemblyName      *pIAssemblyName,
+                                                      /* in */ CLRPrivBinderCoreCLR *pTPABinder,
                                                       /* out */ Assembly           **ppAssembly);
                                                       
         static HRESULT BindUsingPEImage(/* in */  ApplicationContext *pApplicationContext,