Only fail GetBag if there was an IO Error

AssetManager2::GetBag* functions may return "no value" for
the missing resources, that's not an error and shouldn't
result in java exceptions

+ fix the perf regression from extra level of indirection

Bug: 282264161
Test: libandroidfw_tests + boot
Change-Id: Iea32b248b1ca9f6a366b44a14866da16d6b2ef6b
diff --git a/core/jni/android_util_AssetManager.cpp b/core/jni/android_util_AssetManager.cpp
index cac6f08..979c9e3 100644
--- a/core/jni/android_util_AssetManager.cpp
+++ b/core/jni/android_util_AssetManager.cpp
@@ -1126,30 +1126,29 @@
     }
   }
 
-  auto style_stack = assetmanager->GetBagResIdStack(xml_style_res);
-  if (!style_stack.ok()) {
+  const auto maybe_style_stack = assetmanager->GetBagResIdStack(xml_style_res);
+  if (!maybe_style_stack.ok()) {
     jniThrowIOException(env, EBADMSG);
     return nullptr;
   }
-  auto def_style_stack = assetmanager->GetBagResIdStack(def_style_resid);
-  if (!def_style_stack.ok()) {
+  const auto& style_stack = *maybe_style_stack.value();
+  const auto maybe_def_style_stack = assetmanager->GetBagResIdStack(def_style_resid);
+  if (!maybe_def_style_stack.ok()) {
     jniThrowIOException(env, EBADMSG);
     return nullptr;
   }
+  const auto& def_style_stack = *maybe_def_style_stack.value();
 
-  jintArray array = env->NewIntArray(style_stack.value()->size() + def_style_stack.value()->size());
+  jintArray array = env->NewIntArray(style_stack.size() + def_style_stack.size());
   if (env->ExceptionCheck()) {
     return nullptr;
   }
 
-  for (uint32_t i = 0; i < style_stack.value()->size(); i++) {
-    jint attr_resid = (*style_stack.value())[i];
-    env->SetIntArrayRegion(array, i, 1, &attr_resid);
-  }
-  for (uint32_t i = 0; i < def_style_stack.value()->size(); i++) {
-    jint attr_resid = (*def_style_stack.value())[i];
-    env->SetIntArrayRegion(array, style_stack.value()->size() + i, 1, &attr_resid);
-  }
+  static_assert(sizeof(jint) == sizeof(decltype(style_stack.front())));
+  env->SetIntArrayRegion(array, 0, style_stack.size(),
+                         reinterpret_cast<const jint*>(style_stack.data()));
+  env->SetIntArrayRegion(array, style_stack.size(), def_style_stack.size(),
+                         reinterpret_cast<const jint*>(def_style_stack.data()));
   return array;
 }
 
diff --git a/libs/androidfw/AssetManager2.cpp b/libs/androidfw/AssetManager2.cpp
index 61282a0..e3f0c8f 100644
--- a/libs/androidfw/AssetManager2.cpp
+++ b/libs/androidfw/AssetManager2.cpp
@@ -1097,7 +1097,7 @@
   auto [it, inserted] = cached_bag_resid_stacks_.try_emplace(resid);
   if (inserted) {
     // This is a new entry in the cache, need to populate it.
-    if (auto maybe_bag = GetBag(resid, it->second); !maybe_bag.ok()) {
+    if (auto maybe_bag = GetBag(resid, it->second); UNLIKELY(IsIOError(maybe_bag))) {
       cached_bag_resid_stacks_.erase(it);
       return base::unexpected(maybe_bag.error());
     }
@@ -1119,9 +1119,13 @@
 }
 
 base::expected<const ResolvedBag*, NullOrIOError> AssetManager2::GetBag(uint32_t resid) const {
-  std::vector<uint32_t> found_resids;
-  const auto bag = GetBag(resid, found_resids);
-  cached_bag_resid_stacks_.try_emplace(resid, std::move(found_resids));
+  auto [resid_stacks_it, _] = cached_bag_resid_stacks_.try_emplace(resid);
+  resid_stacks_it->second.clear();
+  const auto bag = GetBag(resid, resid_stacks_it->second);
+  if (UNLIKELY(IsIOError(bag))) {
+    cached_bag_resid_stacks_.erase(resid_stacks_it);
+    return base::unexpected(bag.error());
+  }
   return bag;
 }