AAPT2: Workaround for feature splits without namespacing

Android Instant Apps in its current iteration does not use namespaces,
but due to limitations on the Android resource runtime, needs to make
it look like it does.

This is due to a bug that treats any package ID that's not 0x01 or 0x7F
as a shared library. Shared libraries require unique package names.

As a workaround, and since Android Instant Apps can not have a feature
depend on another feature, we can alter the resource package name of a
feature split just before writing it out to disk. This avoids using a
unique package name while linking, thereby avoiding namespace issues.

Bug: 68820737
Test: manual
Change-Id: Ic553ed42656436bbb949393d0248ee7bb9d37860

3 files changed, 62 insertions, 8 deletions

diff --git a/tools/aapt2/ResourceValues.cpp b/tools/aapt2/ResourceValues.cpp
index b38d259d6b25..a782cd3672d1 100644
--- a/tools/aapt2/ResourceValues.cpp
+++ b/tools/aapt2/ResourceValues.cpp
@@ -118,7 +118,7 @@ bool Reference::Equals(const Value* value) const {
 bool Reference::Flatten(android::Res_value* out_value) const {
   const ResourceId resid = id.value_or_default(ResourceId(0));
   const bool dynamic = resid.is_valid_dynamic() && resid.package_id() != kFrameworkPackageId &&
-                       resid.package_id() != kAppPackageId;
+                       resid.package_id() < kAppPackageId;
 
   if (reference_type == Reference::Type::kResource) {
     if (dynamic) {
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index b372923e4010..66b5a7af3677 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -795,6 +795,9 @@ class LinkCommand {
     for (auto& entry : asset_source->GetAssignedPackageIds()) {
       if (entry.first > kFrameworkPackageId && entry.first < kAppPackageId) {
         final_table_.included_packages_[entry.first] = entry.second;
+      } else if (entry.first == kAppPackageId) {
+        // Capture the included base feature package.
+        included_feature_base_ = entry.second;
       }
     }
 
@@ -1465,11 +1468,48 @@ class LinkCommand {
       return false;
     }
 
-    if (!FlattenTable(table, options_.output_format, writer)) {
+    // Hack to fix b/68820737.
+    // We need to modify the ResourceTable's package name, but that should NOT affect
+    // anything else being generated, which includes the Java classes.
+    // If required, the package name is modifed before flattening, and then modified back
+    // to its original name.
+    ResourceTablePackage* package_to_rewrite = nullptr;
+    if (context_->GetPackageId() > kAppPackageId &&
+        included_feature_base_ == make_value(context_->GetCompilationPackage())) {
+      // The base APK is included, and this is a feature split. If the base package is
+      // the same as this package, then we are building an old style Android Instant Apps feature
+      // split and must apply this workaround to avoid requiring namespaces support.
+      package_to_rewrite = table->FindPackage(context_->GetCompilationPackage());
+      if (package_to_rewrite != nullptr) {
+        CHECK_EQ(1u, table->packages.size()) << "can't change name of package when > 1 package";
+
+        std::string new_package_name =
+            StringPrintf("%s.%s", package_to_rewrite->name.c_str(),
+                         app_info_.split_name.value_or_default("feature").c_str());
+
+        if (context_->IsVerbose()) {
+          context_->GetDiagnostics()->Note(
+              DiagMessage() << "rewriting resource package name for feature split to '"
+                            << new_package_name << "'");
+        }
+        package_to_rewrite->name = new_package_name;
+      }
+    }
+
+    bool success = FlattenTable(table, options_.output_format, writer);
+
+    if (package_to_rewrite != nullptr) {
+      // Change the name back.
+      package_to_rewrite->name = context_->GetCompilationPackage();
+      if (package_to_rewrite->id) {
+        table->included_packages_.erase(package_to_rewrite->id.value());
+      }
+    }
+
+    if (!success) {
       context_->GetDiagnostics()->Error(DiagMessage() << "failed to write resource table");
-      return false;
     }
-    return true;
+    return success;
   }
 
   int Run(const std::vector<std::string>& input_files) {
@@ -1498,8 +1538,8 @@ class LinkCommand {
       return 1;
     }
 
-    const AppInfo& app_info = maybe_app_info.value();
-    context_->SetMinSdkVersion(app_info.min_sdk_version.value_or_default(0));
+    app_info_ = maybe_app_info.value();
+    context_->SetMinSdkVersion(app_info_.min_sdk_version.value_or_default(0));
 
     context_->SetNameManglerPolicy(NameManglerPolicy{context_->GetCompilationPackage()});
 
@@ -1699,7 +1739,7 @@ class LinkCommand {
 
         // Generate an AndroidManifest.xml for each split.
         std::unique_ptr<xml::XmlResource> split_manifest =
-            GenerateSplitManifest(app_info, *split_constraints_iter);
+            GenerateSplitManifest(app_info_, *split_constraints_iter);
 
         XmlReferenceLinker linker;
         if (!linker.Consume(context_, split_manifest.get())) {
@@ -1799,6 +1839,8 @@ class LinkCommand {
   LinkContext* context_;
   ResourceTable final_table_;
 
+  AppInfo app_info_;
+
   std::unique_ptr<TableMerger> table_merger_;
 
   // A pointer to the FileCollection representing the filesystem (not archives).
@@ -1816,6 +1858,9 @@ class LinkCommand {
 
   // The set of shared libraries being used, mapping their assigned package ID to package name.
   std::map<size_t, std::string> shared_libs_;
+
+  // The package name of the base application, if it is included.
+  Maybe<std::string> included_feature_base_;
 };
 
 int Link(const std::vector<StringPiece>& args, IDiagnostics* diagnostics) {
diff --git a/tools/aapt2/format/binary/TableFlattener.cpp b/tools/aapt2/format/binary/TableFlattener.cpp
index 4a1b46c99d4b..2a51df3912e3 100644
--- a/tools/aapt2/format/binary/TableFlattener.cpp
+++ b/tools/aapt2/format/binary/TableFlattener.cpp
@@ -23,6 +23,7 @@
 
 #include "android-base/logging.h"
 #include "android-base/macros.h"
+#include "android-base/stringprintf.h"
 
 #include "ResourceTable.h"
 #include "ResourceValues.h"
@@ -579,7 +580,15 @@ bool TableFlattener::Consume(IAaptContext* context, ResourceTable* table) {
       // Write a self mapping entry for this package if the ID is non-standard (0x7f).
       const uint8_t package_id = package->id.value();
       if (package_id != kFrameworkPackageId && package_id != kAppPackageId) {
-        table->included_packages_[package_id] = package->name;
+        auto result = table->included_packages_.insert({package_id, package->name});
+        if (!result.second && result.first->second != package->name) {
+          // A mapping for this package ID already exists, and is a different package. Error!
+          context->GetDiagnostics()->Error(
+              DiagMessage() << android::base::StringPrintf(
+                  "can't map package ID %02x to '%s'. Already mapped to '%s'", package_id,
+                  package->name.c_str(), result.first->second.c_str()));
+          return false;
+        }
       }
     }