[mono] Fix loader incompatibility w.r.t. Resolving event (#54815)

* When loading a non-satellite assembly into a non-default ALC,
  invoke the Resolving event in the default ALC first.

* Fixes https://github.com/dotnet/runtime/issues/54814

1 files changed, 11 insertions, 1 deletions

diff --git a/src/mono/mono/metadata/assembly.c b/src/mono/mono/metadata/assembly.c
index e98264a2f93..8a52e63bc85 100644
--- a/src/mono/mono/metadata/assembly.c
+++ b/src/mono/mono/metadata/assembly.c
@@ -1061,7 +1061,8 @@ netcore_load_reference (MonoAssemblyName *aname, MonoAssemblyLoadContext *alc, M
 	 *
 	 * 7. If this is a satellite request, call the ALC ResolveSatelliteAssembly method.
 	 *
-	 * 8. Call the ALC Resolving event.
+	 * 8. Call the ALC Resolving event.  If the ALC is not the default and this is not
+	 *    a satellite request, call the Resolving event in the default ALC first.
 	 *
 	 * 9. Call the ALC AssemblyResolve event (except for corlib satellite assemblies).
 	 *
@@ -1138,6 +1139,15 @@ netcore_load_reference (MonoAssemblyName *aname, MonoAssemblyLoadContext *alc, M
 		}
 	}
 
+	// For compatibility with CoreCLR, invoke the Resolving event in the default ALC first whenever loading
+	// a non-satellite assembly into a non-default ALC.  See: https://github.com/dotnet/runtime/issues/54814
+	if (!is_default && !is_satellite) {
+		reference = mono_alc_invoke_resolve_using_resolving_event_nofail (mono_alc_get_default (), aname);
+		if (reference) {
+			mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_ASSEMBLY, "Assembly found with the Resolving event (default ALC): '%s'.", aname->name);
+			goto leave;
+		}
+	}
 	reference = mono_alc_invoke_resolve_using_resolving_event_nofail (alc, aname);
 	if (reference) {
 		mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_ASSEMBLY, "Assembly found with the Resolving event: '%s'.", aname->name);