Implement filter-product

filter-product option is added to aapt2 compile, which filters values
with a given product and removes all other values (including default).
The motivation of this change is to generate product-specific RRO
automatically, making a main resource APK (e.g. framework-res.apk)
identical in all targets.

Bug: 294799593
Test: build
Change-Id: I42eb3e134c7aa120f6bbe2d26d311bd46b586595

8 files changed, 214 insertions, 64 deletions

diff --git a/tools/aapt2/Android.bp b/tools/aapt2/Android.bp
index 977b2768e702..fff8f78a5d01 100644
--- a/tools/aapt2/Android.bp
+++ b/tools/aapt2/Android.bp
@@ -122,7 +122,6 @@ cc_library_host_static {
         "link/AutoVersioner.cpp",
         "link/ManifestFixer.cpp",
         "link/NoDefaultResourceRemover.cpp",
-        "link/ProductFilter.cpp",
         "link/PrivateAttributeMover.cpp",
         "link/ReferenceLinker.cpp",
         "link/ResourceExcluder.cpp",
@@ -135,6 +134,7 @@ cc_library_host_static {
         "optimize/ResourceFilter.cpp",
         "optimize/Obfuscator.cpp",
         "optimize/VersionCollapser.cpp",
+        "process/ProductFilter.cpp",
         "process/SymbolTable.cpp",
         "split/TableSplitter.cpp",
         "text/Printer.cpp",
diff --git a/tools/aapt2/cmd/Compile.cpp b/tools/aapt2/cmd/Compile.cpp
index b5c290ec8dad..728ba8aa4fdd 100644
--- a/tools/aapt2/cmd/Compile.cpp
+++ b/tools/aapt2/cmd/Compile.cpp
@@ -45,6 +45,7 @@
 #include "io/StringStream.h"
 #include "io/Util.h"
 #include "io/ZipArchive.h"
+#include "process/ProductFilter.h"
 #include "trace/TraceBuffer.h"
 #include "util/Files.h"
 #include "util/Util.h"
@@ -179,6 +180,15 @@ static bool CompileTable(IAaptContext* context, const CompileOptions& options,
     if (!res_parser.Parse(&xml_parser)) {
       return false;
     }
+
+    if (options.product_.has_value()) {
+      if (!ProductFilter({*options.product_}, /* remove_default_config_values = */ true)
+               .Consume(context, &table)) {
+        context->GetDiagnostics()->Error(android::DiagMessage(path_data.source)
+                                         << "failed to filter product");
+        return false;
+      }
+    }
   }
 
   if (options.pseudolocalize && translatable_file) {
diff --git a/tools/aapt2/cmd/Compile.h b/tools/aapt2/cmd/Compile.h
index 22890fc53d5c..61c5b60adb76 100644
--- a/tools/aapt2/cmd/Compile.h
+++ b/tools/aapt2/cmd/Compile.h
@@ -44,6 +44,7 @@ struct CompileOptions {
   // See comments on aapt::ResourceParserOptions.
   bool preserve_visibility_of_styleables = false;
   bool verbose = false;
+  std::optional<std::string> product_;
 };
 
 /** Parses flags and compiles resources to be used in linking.  */
@@ -87,6 +88,10 @@ class CompileCommand : public Command {
                     "Sets the ratio of resources to generate grammatical gender strings for. The "
                     "ratio has to be a float number between 0 and 1.",
                     &options_.pseudo_localize_gender_ratio);
+    AddOptionalFlag("--filter-product",
+                    "Leave only resources specific to the given product. All "
+                    "other resources (including defaults) are removed.",
+                    &options_.product_);
   }
 
   int Action(const std::vector<std::string>& args) override;
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index eb4e38c5f35f..159c6fd9ef58 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -66,6 +66,7 @@
 #include "optimize/ResourceDeduper.h"
 #include "optimize/VersionCollapser.h"
 #include "process/IResourceTableConsumer.h"
+#include "process/ProductFilter.h"
 #include "process/SymbolTable.h"
 #include "split/TableSplitter.h"
 #include "trace/TraceBuffer.h"
@@ -2128,7 +2129,7 @@ class Linker {
                                          << "can't select products when building static library");
       }
     } else {
-      ProductFilter product_filter(options_.products);
+      ProductFilter product_filter(options_.products, /* remove_default_config_values = */ false);
       if (!product_filter.Consume(context_, &final_table_)) {
         context_->GetDiagnostics()->Error(android::DiagMessage() << "failed stripping products");
         return 1;
diff --git a/tools/aapt2/link/Linkers.h b/tools/aapt2/link/Linkers.h
index 44cd276f77a2..18165f7d489f 100644
--- a/tools/aapt2/link/Linkers.h
+++ b/tools/aapt2/link/Linkers.h
@@ -20,12 +20,12 @@
 #include <set>
 #include <unordered_set>
 
+#include "Resource.h"
+#include "SdkConstants.h"
 #include "android-base/macros.h"
+#include "android-base/result.h"
 #include "androidfw/ConfigDescription.h"
 #include "androidfw/StringPiece.h"
-
-#include "Resource.h"
-#include "SdkConstants.h"
 #include "process/IResourceTableConsumer.h"
 #include "xml/XmlDom.h"
 
@@ -92,28 +92,6 @@ class PrivateAttributeMover : public IResourceTableConsumer {
   DISALLOW_COPY_AND_ASSIGN(PrivateAttributeMover);
 };
 
-class ResourceConfigValue;
-
-class ProductFilter : public IResourceTableConsumer {
- public:
-  using ResourceConfigValueIter = std::vector<std::unique_ptr<ResourceConfigValue>>::iterator;
-
-  explicit ProductFilter(std::unordered_set<std::string> products) : products_(products) {
-  }
-
-  ResourceConfigValueIter SelectProductToKeep(const ResourceNameRef& name,
-                                              const ResourceConfigValueIter begin,
-                                              const ResourceConfigValueIter end,
-                                              android::IDiagnostics* diag);
-
-  bool Consume(IAaptContext* context, ResourceTable* table) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ProductFilter);
-
-  std::unordered_set<std::string> products_;
-};
-
 // Removes namespace nodes and URI information from the XmlResource.
 //
 // Once an XmlResource is processed by this consumer, it is no longer able to have its attributes
diff --git a/tools/aapt2/link/ProductFilter.cpp b/tools/aapt2/process/ProductFilter.cpp
index 9544986fda76..0b1c0a6adb51 100644
--- a/tools/aapt2/link/ProductFilter.cpp
+++ b/tools/aapt2/process/ProductFilter.cpp
@@ -14,16 +14,18 @@
  * limitations under the License.
  */
 
-#include "link/Linkers.h"
+#include "process/ProductFilter.h"
+
+#include <algorithm>
 
 #include "ResourceTable.h"
 #include "trace/TraceBuffer.h"
 
 namespace aapt {
 
-ProductFilter::ResourceConfigValueIter ProductFilter::SelectProductToKeep(
-    const ResourceNameRef& name, const ResourceConfigValueIter begin,
-    const ResourceConfigValueIter end, android::IDiagnostics* diag) {
+std::optional<ProductFilter::ResourceConfigValueIter> ProductFilter::SelectProductToKeep(
+    const ResourceNameRef& name, ResourceConfigValueIter begin, ResourceConfigValueIter end,
+    android::IDiagnostics* diag) {
   ResourceConfigValueIter default_product_iter = end;
   ResourceConfigValueIter selected_product_iter = end;
 
@@ -36,12 +38,11 @@ ProductFilter::ResourceConfigValueIter ProductFilter::SelectProductToKeep(
                     << "selection of product '" << config_value->product << "' for resource "
                     << name << " is ambiguous");
 
-        ResourceConfigValue* previously_selected_config_value =
-            selected_product_iter->get();
+        ResourceConfigValue* previously_selected_config_value = selected_product_iter->get();
         diag->Note(android::DiagMessage(previously_selected_config_value->value->GetSource())
                    << "product '" << previously_selected_config_value->product
                    << "' is also a candidate");
-        return end;
+        return std::nullopt;
       }
 
       // Select this product.
@@ -54,11 +55,10 @@ ProductFilter::ResourceConfigValueIter ProductFilter::SelectProductToKeep(
         diag->Error(android::DiagMessage(config_value->value->GetSource())
                     << "multiple default products defined for resource " << name);
 
-        ResourceConfigValue* previously_default_config_value =
-            default_product_iter->get();
+        ResourceConfigValue* previously_default_config_value = default_product_iter->get();
         diag->Note(android::DiagMessage(previously_default_config_value->value->GetSource())
                    << "default product also defined here");
-        return end;
+        return std::nullopt;
       }
 
       // Mark the default.
@@ -66,9 +66,16 @@ ProductFilter::ResourceConfigValueIter ProductFilter::SelectProductToKeep(
     }
   }
 
+  if (remove_default_config_values_) {
+    // If we are leaving only a specific product, return early here instead of selecting the default
+    // value. Returning end here will cause this value set to be skipped, and will be removed with
+    // ClearEmptyValues method.
+    return selected_product_iter;
+  }
+
   if (default_product_iter == end) {
     diag->Error(android::DiagMessage() << "no default product defined for resource " << name);
-    return end;
+    return std::nullopt;
   }
 
   if (selected_product_iter == end) {
@@ -89,20 +96,27 @@ bool ProductFilter::Consume(IAaptContext* context, ResourceTable* table) {
         ResourceConfigValueIter start_range_iter = iter;
         while (iter != entry->values.end()) {
           ++iter;
-          if (iter == entry->values.end() ||
-              (*iter)->config != (*start_range_iter)->config) {
+          if (iter == entry->values.end() || (*iter)->config != (*start_range_iter)->config) {
             // End of the array, or we saw a different config,
             // so this must be the end of a range of products.
             // Select the product to keep from the set of products defined.
             ResourceNameRef name(pkg->name, type->named_type, entry->name);
-            auto value_to_keep = SelectProductToKeep(
-                name, start_range_iter, iter, context->GetDiagnostics());
-            if (value_to_keep == iter) {
+            auto value_to_keep =
+                SelectProductToKeep(name, start_range_iter, iter, context->GetDiagnostics());
+            if (!value_to_keep.has_value()) {
               // An error occurred, we could not pick a product.
               error = true;
-            } else {
+            } else if (auto val = value_to_keep.value(); val != iter) {
               // We selected a product to keep. Move it to the new array.
-              new_values.push_back(std::move(*value_to_keep));
+              if (remove_default_config_values_) {
+                // We are filtering values with the given product. The selected value here will be
+                // a new default value, and all other values will be removed.
+                new_values.push_back(
+                    std::make_unique<ResourceConfigValue>((*val)->config, android::StringPiece{}));
+                new_values.back()->value = std::move((*val)->value);
+              } else {
+                new_values.push_back(std::move(*val));
+              }
             }
 
             // Start the next range of products.
@@ -115,7 +129,27 @@ bool ProductFilter::Consume(IAaptContext* context, ResourceTable* table) {
       }
     }
   }
+
+  if (remove_default_config_values_) {
+    ClearEmptyValues(table);
+  }
+
   return !error;
 }
 
+void ProductFilter::ClearEmptyValues(ResourceTable* table) {
+  // Clear any empty packages/types/entries, as remove_default_config_values_ may remove an entire
+  // value set.
+  CHECK(remove_default_config_values_)
+      << __func__ << " should only be called when remove_default_config_values_ is set";
+
+  for (auto& pkg : table->packages) {
+    for (auto& type : pkg->types) {
+      std::erase_if(type->entries, [](auto& entry) { return entry->values.empty(); });
+    }
+    std::erase_if(pkg->types, [](auto& type) { return type->entries.empty(); });
+  }
+  std::erase_if(table->packages, [](auto& package) { return package->types.empty(); });
+}
+
 }  // namespace aapt
diff --git a/tools/aapt2/process/ProductFilter.h b/tools/aapt2/process/ProductFilter.h
new file mode 100644
index 000000000000..0ec2f00863fc
--- /dev/null
+++ b/tools/aapt2/process/ProductFilter.h
@@ -0,0 +1,65 @@
+#pragma once
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "Resource.h"
+#include "android-base/macros.h"
+#include "androidfw/ConfigDescription.h"
+#include "androidfw/IDiagnostics.h"
+#include "process/IResourceTableConsumer.h"
+
+namespace aapt {
+
+class ResourceConfigValue;
+
+class ProductFilter : public IResourceTableConsumer {
+ public:
+  using ResourceConfigValueIter = std::vector<std::unique_ptr<ResourceConfigValue>>::iterator;
+
+  // Setting remove_default_config_values will remove all values other than
+  // specified product, including default. For example, if the following table
+  //
+  //     <string name="foo" product="default">foo_default</string>
+  //     <string name="foo" product="tablet">foo_tablet</string>
+  //     <string name="bar">bar</string>
+  //
+  // is consumed with tablet, it will result in
+  //
+  //     <string name="foo">foo_tablet</string>
+  //
+  // removing foo_default and bar. This option is to generate an RRO package
+  // with given product.
+  explicit ProductFilter(std::unordered_set<std::string> products,
+                         bool remove_default_config_values)
+      : products_(std::move(products)),
+        remove_default_config_values_(remove_default_config_values) {
+  }
+
+  bool Consume(IAaptContext* context, ResourceTable* table) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ProductFilter);
+
+  // SelectProductToKeep returns an iterator for the selected value.
+  //
+  // Returns std::nullopt in case of failure (e.g. ambiguous values, missing or duplicated default
+  // values).
+  // Returns `end` if keep_as_default_product is set and no value for the specified product was
+  // found.
+  std::optional<ResourceConfigValueIter> SelectProductToKeep(const ResourceNameRef& name,
+                                                             ResourceConfigValueIter begin,
+                                                             ResourceConfigValueIter end,
+                                                             android::IDiagnostics* diag);
+
+  void ClearEmptyValues(ResourceTable* table);
+
+  std::unordered_set<std::string> products_;
+  bool remove_default_config_values_;
+};
+
+}  // namespace aapt
diff --git a/tools/aapt2/link/ProductFilter_test.cpp b/tools/aapt2/process/ProductFilter_test.cpp
index 2cb9afa05cad..27a82dcc3453 100644
--- a/tools/aapt2/link/ProductFilter_test.cpp
+++ b/tools/aapt2/process/ProductFilter_test.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "link/Linkers.h"
+#include "process/ProductFilter.h"
 
 #include "test/Test.h"
 
@@ -57,17 +57,15 @@ TEST(ProductFilterTest, SelectTwoProducts) {
           .Build(),
       context->GetDiagnostics()));
 
-  ProductFilter filter({"tablet"});
+  ProductFilter filter({"tablet"}, /* remove_default_config_values = */ false);
   ASSERT_TRUE(filter.Consume(context.get(), &table));
 
-  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one", land, ""));
-  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one", land, "tablet"));
-  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one", port, ""));
-  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one", port, "tablet"));
+  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", land, ""));
+  EXPECT_NE(nullptr,
+            test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", land, "tablet"));
+  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", port, ""));
+  EXPECT_NE(nullptr,
+            test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", port, "tablet"));
 }
 
 TEST(ProductFilterTest, SelectDefaultProduct) {
@@ -88,15 +86,15 @@ TEST(ProductFilterTest, SelectDefaultProduct) {
       context->GetDiagnostics()));
   ;
 
-  ProductFilter filter(std::unordered_set<std::string>{});
+  ProductFilter filter(std::unordered_set<std::string>{},
+                       /* remove_default_config_values = */ false);
   ASSERT_TRUE(filter.Consume(context.get(), &table));
 
-  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one",
-                         ConfigDescription::DefaultConfig(), ""));
-  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(
-                         &table, "android:string/one",
-                         ConfigDescription::DefaultConfig(), "tablet"));
+  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/one",
+                                                           ConfigDescription::DefaultConfig(), ""));
+  EXPECT_EQ(nullptr,
+            test::GetValueForConfigAndProduct<Id>(&table, "android:string/one",
+                                                  ConfigDescription::DefaultConfig(), "tablet"));
 }
 
 TEST(ProductFilterTest, FailOnAmbiguousProduct) {
@@ -123,7 +121,7 @@ TEST(ProductFilterTest, FailOnAmbiguousProduct) {
           .Build(),
       context->GetDiagnostics()));
 
-  ProductFilter filter({"tablet", "no-sdcard"});
+  ProductFilter filter({"tablet", "no-sdcard"}, /* remove_default_config_values = */ false);
   ASSERT_FALSE(filter.Consume(context.get(), &table));
 }
 
@@ -144,8 +142,67 @@ TEST(ProductFilterTest, FailOnMultipleDefaults) {
           .Build(),
       context->GetDiagnostics()));
 
-  ProductFilter filter(std::unordered_set<std::string>{});
+  ProductFilter filter(std::unordered_set<std::string>{},
+                       /* remove_default_config_values = */ false);
   ASSERT_FALSE(filter.Consume(context.get(), &table));
 }
 
+TEST(ProductFilterTest, RemoveDefaultConfigValues) {
+  std::unique_ptr<IAaptContext> context = test::ContextBuilder().Build();
+
+  const ConfigDescription land = test::ParseConfigOrDie("land");
+  const ConfigDescription port = test::ParseConfigOrDie("port");
+
+  ResourceTable table;
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/one"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("land/default.xml")).Build(),
+                    land)
+          .Build(),
+      context->GetDiagnostics()));
+
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/one"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("land/tablet.xml")).Build(),
+                    land, "tablet")
+          .Build(),
+      context->GetDiagnostics()));
+
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/two"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("land/default.xml")).Build(),
+                    land)
+          .Build(),
+      context->GetDiagnostics()));
+
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/one"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("port/default.xml")).Build(),
+                    port)
+          .Build(),
+      context->GetDiagnostics()));
+
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/one"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("port/tablet.xml")).Build(),
+                    port, "tablet")
+          .Build(),
+      context->GetDiagnostics()));
+
+  ASSERT_TRUE(table.AddResource(
+      NewResourceBuilder(test::ParseNameOrDie("android:string/two"))
+          .SetValue(test::ValueBuilder<Id>().SetSource(android::Source("port/default.xml")).Build(),
+                    port)
+          .Build(),
+      context->GetDiagnostics()));
+
+  ProductFilter filter({"tablet"}, /* remove_default_config_values = */ true);
+  ASSERT_TRUE(filter.Consume(context.get(), &table));
+
+  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", land, ""));
+  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/two", land, ""));
+  EXPECT_NE(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/one", port, ""));
+  EXPECT_EQ(nullptr, test::GetValueForConfigAndProduct<Id>(&table, "android:string/two", port, ""));
+}
+
 }  // namespace aapt