Return empty IL2CPP class helper when metadata is unavailable

.github/workflows/ci.yaml

@@ -189,6 +189,13 @@ jobs:
         shell: pwsh
         run: sccache --zero-stats
 
+      - name: Test IL2CPP class lookup
+        run: |
+          xmake build -y il2cpp-class-lookup-tests
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          xmake run il2cpp-class-lookup-tests
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+
       - name: Build
         run: xmake build -y stfc-community-mod
 
@@ -469,6 +476,11 @@ jobs:
         shell: bash
         run: sccache --zero-stats
 
+      - name: Test IL2CPP class lookup
+        run: |
+          xmake build -y il2cpp-class-lookup-tests
+          xmake run il2cpp-class-lookup-tests
+
       - name: Build
         # -D keeps the existing XMake compiler-cache diagnostics too.
         run: xmake -y -D

mods/src/il2cpp/il2cpp_helper.h

@@ -337,10 +337,10 @@ class IL2CppClassHelper
 inline IL2CppClassHelper il2cpp_get_class_helper_impl(const char* assembly, const char* namespacez, const char* name)
 {
   auto domain    = il2cpp_domain_get();
-  auto assemblyT = il2cpp_domain_assembly_open(domain, assembly);
-  auto image     = il2cpp_assembly_get_image(assemblyT);
+  auto assemblyT = domain ? il2cpp_domain_assembly_open(domain, assembly) : nullptr;
+  auto image     = assemblyT ? il2cpp_assembly_get_image(assemblyT) : nullptr;
 
-  auto cls = il2cpp_class_from_name(image, namespacez, name);
+  auto cls = image ? il2cpp_class_from_name(image, namespacez, name) : nullptr;
 
   return IL2CppClassHelper{cls};
 }

tests/il2cpp_class_lookup.cc

@@ -0,0 +1,71 @@
+// Production helpers with a controlled IL2CPP boundary, on Windows and macOS.
+#include <il2cpp-config.h>
+#if _WIN32
+#undef IL2CPP_IMPORT
+#define IL2CPP_IMPORT
+#endif
+#include "il2cpp/il2cpp_helper.h"
+#include <cstdlib>
+#include <iostream>
+#include <stdexcept>
+
+namespace
+{
+Il2CppClass  klass;
+Il2CppObject object{};
+MethodInfo   method{};
+int          stage = 3;
+} // namespace
+#if _WIN32
+#define API(ret, name, params) extern "C" ret name params
+#define END_API
+#else
+#define API(ret, name, params) name##_t name = +[] params->ret
+#define END_API ;
+#endif
+API(Il2CppDomain*, il2cpp_domain_get, ())
+{ return stage >= 0 ? reinterpret_cast<Il2CppDomain*>(&object) : nullptr; }
+END_API
+API(const Il2CppAssembly*, il2cpp_domain_assembly_open, (Il2CppDomain * domain, const char*))
+{
+  if (!domain)
+    std::abort();
+  return stage >= 1 ? reinterpret_cast<Il2CppAssembly*>(&object) : nullptr;
+}
+END_API
+API(const Il2CppImage*, il2cpp_assembly_get_image, (const Il2CppAssembly* assembly))
+{
+  if (!assembly)
+    std::abort();
+  return stage >= 2 ? reinterpret_cast<Il2CppImage*>(&object) : nullptr;
+}
+END_API
+API(Il2CppClass*, il2cpp_class_from_name, (const Il2CppImage* image, const char*, const char*))
+{
+  if (!image)
+    std::abort();
+  return stage >= 3 ? &klass : nullptr;
+}
+END_API
+API(const MethodInfo*, il2cpp_class_get_method_from_name, (Il2CppClass * cls, const char*, int))
+{
+  if (!cls)
+    std::abort();
+  return &method;
+}
+END_API
+void Require(bool condition)
+{
+  if (!condition)
+    throw std::runtime_error("class lookup regression");
+}
+int main()
+{
+  for (stage = -1; stage < 3; ++stage)
+    Require(!il2cpp_get_class_helper("Assembly", "Namespace", "Class").get_cls());
+  Require(il2cpp_get_class_helper("Assembly", "Namespace", "Class").get_cls() == &klass);
+  Require(!IL2CppClassHelper(nullptr).GetMethodInfo("Method", 0));
+  Require(IL2CppClassHelper(&klass).GetMethodInfo("Method", 0) == &method);
+
+  std::cout << "IL2CPP class lookup regressions passed\n";
+}

xmake.lua

@@ -26,3 +26,14 @@ add_rules("mode.releasedbg")
 includes("xmake/rules/protobuf_sccache.lua")
 includes("xmake/rules/cxx_sccache.lua")
 includes("mods")
+
+target("il2cpp-class-lookup-tests")
+    set_kind("binary")
+    set_default(false)
+    add_files("tests/il2cpp_class_lookup.cc")
+    add_includedirs("mods/src")
+    add_packages("libil2cpp", "eastl")
+    set_exceptions("cxx")
+    if is_plat("windows") then
+        add_linkdirs("mods/src/il2cpp")
+    end