Revert "Revert "[res] Don't create extra asset provider when not..."

Revert submission 31216694-revert-31021037-TXGRFMNZKV

Reason for revert: relanding with a fix
The fix is to still return a null AssetsProvider when failing
to open the supplied apk, instead of ending up with an
empty provider that will fail later

Reverted changes: /q/submissionid:31216694-revert-31021037-TXGRFMNZKV

Change-Id: Ia8e2cdaddf81683cd58547942d1da3c5df93b087

2 files changed, 28 insertions, 4 deletions

diff --git a/libs/androidfw/AssetsProvider.cpp b/libs/androidfw/AssetsProvider.cpp
index 59c6aba7b8b0..808509120462 100644
--- a/libs/androidfw/AssetsProvider.cpp
+++ b/libs/androidfw/AssetsProvider.cpp
@@ -24,9 +24,27 @@
 #include <ziparchive/zip_archive.h>
 
 namespace android {
-namespace {
-constexpr const char* kEmptyDebugString = "<empty>";
-} // namespace
+
+static constexpr std::string_view kEmptyDebugString = "<empty>";
+
+std::unique_ptr<AssetsProvider> AssetsProvider::CreateWithOverride(
+    std::unique_ptr<AssetsProvider> provider, std::unique_ptr<AssetsProvider> override) {
+  if (provider == nullptr) {
+    return {};
+  }
+  if (override == nullptr) {
+    return provider;
+  }
+  return MultiAssetsProvider::Create(std::move(override), std::move(provider));
+}
+
+std::unique_ptr<AssetsProvider> AssetsProvider::CreateFromNullable(
+    std::unique_ptr<AssetsProvider> nullable) {
+  if (nullable) {
+    return nullable;
+  }
+  return EmptyAssetsProvider::Create();
+}
 
 std::unique_ptr<Asset> AssetsProvider::Open(const std::string& path, Asset::AccessMode mode,
                                             bool* file_exists) const {
@@ -425,7 +443,7 @@ const std::string& EmptyAssetsProvider::GetDebugName() const {
   if (path_.has_value()) {
     return *path_;
   }
-  const static std::string kEmpty = kEmptyDebugString;
+  constexpr static std::string kEmpty{kEmptyDebugString};
   return kEmpty;
 }
 
diff --git a/libs/androidfw/include/androidfw/AssetsProvider.h b/libs/androidfw/include/androidfw/AssetsProvider.h
index 46d7a57ab763..037f684f5b78 100644
--- a/libs/androidfw/include/androidfw/AssetsProvider.h
+++ b/libs/androidfw/include/androidfw/AssetsProvider.h
@@ -36,6 +36,12 @@ namespace android {
 struct AssetsProvider {
   static constexpr off64_t kUnknownLength = -1;
 
+  static std::unique_ptr<AssetsProvider> CreateWithOverride(
+      std::unique_ptr<AssetsProvider> provider, std::unique_ptr<AssetsProvider> override);
+
+  static std::unique_ptr<AssetsProvider> CreateFromNullable(
+      std::unique_ptr<AssetsProvider> nullable);
+
   // Opens a file for reading. If `file_exists` is not null, it will be set to `true` if the file
   // exists. This is useful for determining if the file exists but was unable to be opened due to
   // an I/O error.