AAPT2: Remove resources that define locales but no default values.

According to our docs:
https://developer.android.com/guide/topics/resources/localization.html#defaults-r-important

Some resources *require* that there is a default definition. So far,
the pain is felt when doing translations for strings that have been
renamed, etc.

This CL strips out resources that don't have a default value and define
a resource for a locale. This is conservative, but should be expanded
to other configuration properties moving forward.

Bug: 36572857
Test: make aapt2_tests
Change-Id: Ife94a1f8a2ee221f8532ffa856541a9c8c4e7143
diff --git a/tools/aapt2/Android.bp b/tools/aapt2/Android.bp
index eb3a99a..2ff92e6 100644
--- a/tools/aapt2/Android.bp
+++ b/tools/aapt2/Android.bp
@@ -101,6 +101,7 @@
         "io/ZipArchive.cpp",
         "link/AutoVersioner.cpp",
         "link/ManifestFixer.cpp",
+        "link/NoDefaultResourceRemover.cpp",
         "link/ProductFilter.cpp",
         "link/PrivateAttributeMover.cpp",
         "link/ReferenceLinker.cpp",
diff --git a/tools/aapt2/ResourceTable.cpp b/tools/aapt2/ResourceTable.cpp
index 95bf921..d0faac3 100644
--- a/tools/aapt2/ResourceTable.cpp
+++ b/tools/aapt2/ResourceTable.cpp
@@ -162,7 +162,7 @@
   const StringPiece& product;
 };
 
-bool ltConfigKeyRef(const std::unique_ptr<ResourceConfigValue>& lhs, const ConfigKey& rhs) {
+bool lt_config_key_ref(const std::unique_ptr<ResourceConfigValue>& lhs, const ConfigKey& rhs) {
   int cmp = lhs->config.compare(*rhs.config);
   if (cmp == 0) {
     cmp = StringPiece(lhs->product).compare(rhs.product);
@@ -172,8 +172,8 @@
 
 ResourceConfigValue* ResourceEntry::FindValue(const ConfigDescription& config,
                                               const StringPiece& product) {
-  auto iter =
-      std::lower_bound(values.begin(), values.end(), ConfigKey{&config, product}, ltConfigKeyRef);
+  auto iter = std::lower_bound(values.begin(), values.end(), ConfigKey{&config, product},
+                               lt_config_key_ref);
   if (iter != values.end()) {
     ResourceConfigValue* value = iter->get();
     if (value->config == config && StringPiece(value->product) == product) {
@@ -185,8 +185,8 @@
 
 ResourceConfigValue* ResourceEntry::FindOrCreateValue(const ConfigDescription& config,
                                                       const StringPiece& product) {
-  auto iter =
-      std::lower_bound(values.begin(), values.end(), ConfigKey{&config, product}, ltConfigKeyRef);
+  auto iter = std::lower_bound(values.begin(), values.end(), ConfigKey{&config, product},
+                               lt_config_key_ref);
   if (iter != values.end()) {
     ResourceConfigValue* value = iter->get();
     if (value->config == config && StringPiece(value->product) == product) {
@@ -220,15 +220,16 @@
   return results;
 }
 
-std::vector<ResourceConfigValue*> ResourceEntry::FindValuesIf(
-    const std::function<bool(ResourceConfigValue*)>& f) {
-  std::vector<ResourceConfigValue*> results;
-  for (auto& configValue : values) {
-    if (f(configValue.get())) {
-      results.push_back(configValue.get());
+bool ResourceEntry::HasDefaultValue() const {
+  const ConfigDescription& default_config = ConfigDescription::DefaultConfig();
+
+  // The default config should be at the top of the list, since the list is sorted.
+  for (auto& config_value : values) {
+    if (config_value->config == default_config) {
+      return true;
     }
   }
-  return results;
+  return false;
 }
 
 // The default handler for collisions.
diff --git a/tools/aapt2/ResourceTable.h b/tools/aapt2/ResourceTable.h
index 374fe1e..8534eaa 100644
--- a/tools/aapt2/ResourceTable.h
+++ b/tools/aapt2/ResourceTable.h
@@ -104,13 +104,26 @@
   explicit ResourceEntry(const android::StringPiece& name) : name(name.to_string()) {}
 
   ResourceConfigValue* FindValue(const ConfigDescription& config);
+
   ResourceConfigValue* FindValue(const ConfigDescription& config,
                                  const android::StringPiece& product);
+
   ResourceConfigValue* FindOrCreateValue(const ConfigDescription& config,
                                          const android::StringPiece& product);
   std::vector<ResourceConfigValue*> FindAllValues(const ConfigDescription& config);
-  std::vector<ResourceConfigValue*> FindValuesIf(
-      const std::function<bool(ResourceConfigValue*)>& f);
+
+  template <typename Func>
+  std::vector<ResourceConfigValue*> FindValuesIf(Func f) {
+    std::vector<ResourceConfigValue*> results;
+    for (auto& config_value : values) {
+      if (f(config_value.get())) {
+        results.push_back(config_value.get());
+      }
+    }
+    return results;
+  }
+
+  bool HasDefaultValue() const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ResourceEntry);
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index 12ab883..0839f6f 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -55,6 +55,7 @@
 #include "java/ProguardRules.h"
 #include "link/Linkers.h"
 #include "link/ManifestFixer.h"
+#include "link/NoDefaultResourceRemover.h"
 #include "link/ReferenceLinker.h"
 #include "link/TableMerger.h"
 #include "link/XmlCompatVersioner.h"
@@ -1785,6 +1786,14 @@
           util::make_unique<FeatureSplitSymbolTableDelegate>(context_));
     }
 
+    // Before we process anything, remove the resources whose default values don't exist.
+    // We want to force any references to these to fail the build.
+    if (!NoDefaultResourceRemover{}.Consume(context_, &final_table_)) {
+      context_->GetDiagnostics()->Error(DiagMessage()
+                                        << "failed removing resources with no defaults");
+      return 1;
+    }
+
     ReferenceLinker linker;
     if (!linker.Consume(context_, &final_table_)) {
       context_->GetDiagnostics()->Error(DiagMessage() << "failed linking references");
diff --git a/tools/aapt2/link/NoDefaultResourceRemover.cpp b/tools/aapt2/link/NoDefaultResourceRemover.cpp
new file mode 100644
index 0000000..cfb4b26
--- /dev/null
+++ b/tools/aapt2/link/NoDefaultResourceRemover.cpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "link/NoDefaultResourceRemover.h"
+
+#include <algorithm>
+
+#include "ResourceTable.h"
+
+namespace aapt {
+
+static bool IsDefaultConfigRequired(const ConfigDescription& config) {
+  // We don't want to be overzealous with resource removal, so have strict requirements.
+  // If a resource defines a value for a locale-only configuration, the default configuration is
+  // required.
+  if (ConfigDescription::DefaultConfig().diff(config) == ConfigDescription::CONFIG_LOCALE) {
+    return true;
+  }
+  return false;
+}
+
+static bool KeepResource(const std::unique_ptr<ResourceEntry>& entry) {
+  if (entry->visibility.level == Visibility::Level::kPublic) {
+    // Removing a public API without the developer knowing is bad, so just leave this here for now.
+    return true;
+  }
+
+  if (entry->HasDefaultValue()) {
+    // There is a default value, no removal needed.
+    return true;
+  }
+
+  // There is no default value defined, check if removal is required.
+  for (const auto& config_value : entry->values) {
+    if (IsDefaultConfigRequired(config_value->config)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool NoDefaultResourceRemover::Consume(IAaptContext* context, ResourceTable* table) {
+  const ConfigDescription default_config = ConfigDescription::DefaultConfig();
+  for (auto& pkg : table->packages) {
+    for (auto& type : pkg->types) {
+      const auto end_iter = type->entries.end();
+      const auto new_end_iter =
+          std::stable_partition(type->entries.begin(), end_iter, KeepResource);
+      for (auto iter = new_end_iter; iter != end_iter; ++iter) {
+        const ResourceName name(pkg->name, type->type, (*iter)->name);
+        IDiagnostics* diag = context->GetDiagnostics();
+        diag->Warn(DiagMessage() << "removing resource " << name
+                                 << " without required default value");
+        if (context->IsVerbose()) {
+          diag->Note(DiagMessage() << "  did you forget to remove all definitions?");
+          for (const auto& config_value : (*iter)->values) {
+            if (config_value->value != nullptr) {
+              diag->Note(DiagMessage(config_value->value->GetSource()) << "defined here");
+            }
+          }
+        }
+      }
+
+      type->entries.erase(new_end_iter, type->entries.end());
+    }
+  }
+  return true;
+}
+
+}  // namespace aapt
diff --git a/tools/aapt2/link/NoDefaultResourceRemover.h b/tools/aapt2/link/NoDefaultResourceRemover.h
new file mode 100644
index 0000000..7582ef3
--- /dev/null
+++ b/tools/aapt2/link/NoDefaultResourceRemover.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef AAPT_LINK_NODEFAULTRESOURCEREMOVER_H
+#define AAPT_LINK_NODEFAULTRESOURCEREMOVER_H
+
+#include "android-base/macros.h"
+
+#include "process/IResourceTableConsumer.h"
+
+namespace aapt {
+
+// Removes any resource for which there exists no definition for the default configuration, where
+// for that resource type, a definition is required.
+//
+// The obvious example is when defining localized strings. If a string in the default configuration
+// has its name changed, the translations for that string won't be changed but will still cause
+// the generated R class to contain the old string name. This will cause breakages in apps that
+// still rely on the old name when the translations are updated.
+class NoDefaultResourceRemover : public IResourceTableConsumer {
+ public:
+  NoDefaultResourceRemover() = default;
+
+  bool Consume(IAaptContext* context, ResourceTable* table) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NoDefaultResourceRemover);
+};
+
+}  // namespace aapt
+
+#endif  // AAPT_LINK_NODEFAULTRESOURCEREMOVER_H
diff --git a/tools/aapt2/link/NoDefaultResourceRemover_test.cpp b/tools/aapt2/link/NoDefaultResourceRemover_test.cpp
new file mode 100644
index 0000000..943709a
--- /dev/null
+++ b/tools/aapt2/link/NoDefaultResourceRemover_test.cpp
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "link/NoDefaultResourceRemover.h"
+
+#include "test/Test.h"
+
+namespace aapt {
+
+TEST(NoDefaultResourceRemoverTest, RemoveEntryWithNoDefaultAndOnlyLocales) {
+  std::unique_ptr<IAaptContext> context = test::ContextBuilder().Build();
+  std::unique_ptr<ResourceTable> table =
+      test::ResourceTableBuilder()
+          .SetPackageId("android", 0x01)
+          .AddSimple("android:string/foo")
+          .AddSimple("android:string/foo", test::ParseConfigOrDie("en-rGB"))
+          .AddSimple("android:string/foo", test::ParseConfigOrDie("fr-rFR"))
+          .AddSimple("android:string/bar", test::ParseConfigOrDie("en-rGB"))
+          .AddSimple("android:string/bar", test::ParseConfigOrDie("fr-rFR"))
+          .AddSimple("android:string/bat", test::ParseConfigOrDie("en-rGB-xhdpi"))
+          .AddSimple("android:string/bat", test::ParseConfigOrDie("fr-rFR-hdpi"))
+          .AddSimple("android:string/baz", test::ParseConfigOrDie("en-rGB"))
+          .AddSimple("android:string/baz", test::ParseConfigOrDie("fr-rFR"))
+          .SetSymbolState("android:string/baz", ResourceId(0x01020002), Visibility::Level::kPublic)
+          .Build();
+
+  NoDefaultResourceRemover remover;
+  ASSERT_TRUE(remover.Consume(context.get(), table.get()));
+
+  EXPECT_TRUE(table->FindResource(test::ParseNameOrDie("android:string/foo")));
+  EXPECT_FALSE(table->FindResource(test::ParseNameOrDie("android:string/bar")));
+  EXPECT_TRUE(table->FindResource(test::ParseNameOrDie("android:string/bat")));
+  EXPECT_TRUE(table->FindResource(test::ParseNameOrDie("android:string/baz")));
+}
+
+}  // namespace aapt