[aapt2] Implement FeatureFlagsFilter
FeatureFlagsFilter looks for `android:featureFlag` attributes in the XML
and removes elements according to the given flag values.
Bug: 297373084
Test: atest aapt2_tests
Change-Id: Icf97de2152c0c53b0b4518ae837e0d198873d1c5
diff --git a/tools/aapt2/Android.bp b/tools/aapt2/Android.bp
index ed3e1ac..40cba3e 100644
--- a/tools/aapt2/Android.bp
+++ b/tools/aapt2/Android.bp
@@ -119,6 +119,7 @@
"io/Util.cpp",
"io/ZipArchive.cpp",
"link/AutoVersioner.cpp",
+ "link/FeatureFlagsFilter.cpp",
"link/ManifestFixer.cpp",
"link/NoDefaultResourceRemover.cpp",
"link/PrivateAttributeMover.cpp",
diff --git a/tools/aapt2/link/FeatureFlagsFilter.cpp b/tools/aapt2/link/FeatureFlagsFilter.cpp
new file mode 100644
index 0000000..fdf3f74
--- /dev/null
+++ b/tools/aapt2/link/FeatureFlagsFilter.cpp
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2023 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/FeatureFlagsFilter.h"
+
+#include <string_view>
+
+#include "androidfw/IDiagnostics.h"
+#include "androidfw/Source.h"
+#include "util/Util.h"
+#include "xml/XmlDom.h"
+#include "xml/XmlUtil.h"
+
+using ::aapt::xml::Element;
+using ::aapt::xml::Node;
+using ::aapt::xml::NodeCast;
+
+namespace aapt {
+
+class FlagsVisitor : public xml::Visitor {
+ public:
+ explicit FlagsVisitor(android::IDiagnostics* diagnostics,
+ const FeatureFlagValues& feature_flag_values,
+ const FeatureFlagsFilterOptions& options)
+ : diagnostics_(diagnostics), feature_flag_values_(feature_flag_values), options_(options) {
+ }
+
+ void Visit(xml::Element* node) override {
+ std::erase_if(node->children,
+ [this](std::unique_ptr<xml::Node>& node) { return ShouldRemove(node); });
+ VisitChildren(node);
+ }
+
+ bool HasError() const {
+ return has_error_;
+ }
+
+ private:
+ bool ShouldRemove(std::unique_ptr<xml::Node>& node) {
+ if (const auto* el = NodeCast<Element>(node.get())) {
+ auto* attr = el->FindAttribute(xml::kSchemaAndroid, "featureFlag");
+ if (attr == nullptr) {
+ return false;
+ }
+
+ bool negated = false;
+ std::string_view flag_name = util::TrimWhitespace(attr->value);
+ if (flag_name.starts_with('!')) {
+ negated = true;
+ flag_name = flag_name.substr(1);
+ }
+
+ if (auto it = feature_flag_values_.find(std::string(flag_name));
+ it != feature_flag_values_.end()) {
+ if (it->second.has_value()) {
+ if (options_.remove_disabled_elements) {
+ // Remove if flag==true && attr=="!flag" (negated) OR flag==false && attr=="flag"
+ return *it->second == negated;
+ }
+ } else if (options_.flags_must_have_value) {
+ diagnostics_->Error(android::DiagMessage(node->line_number)
+ << "attribute 'android:featureFlag' has flag '" << flag_name
+ << "' without a true/false value from --feature_flags parameter");
+ has_error_ = true;
+ return false;
+ }
+ } else if (options_.fail_on_unrecognized_flags) {
+ diagnostics_->Error(android::DiagMessage(node->line_number)
+ << "attribute 'android:featureFlag' has flag '" << flag_name
+ << "' not found in flags from --feature_flags parameter");
+ has_error_ = true;
+ return false;
+ }
+ }
+
+ return false;
+ }
+
+ android::IDiagnostics* diagnostics_;
+ const FeatureFlagValues& feature_flag_values_;
+ const FeatureFlagsFilterOptions& options_;
+ bool has_error_ = false;
+};
+
+bool FeatureFlagsFilter::Consume(IAaptContext* context, xml::XmlResource* doc) {
+ FlagsVisitor visitor(context->GetDiagnostics(), feature_flag_values_, options_);
+ doc->root->Accept(&visitor);
+ return !visitor.HasError();
+}
+
+} // namespace aapt
diff --git a/tools/aapt2/link/FeatureFlagsFilter.h b/tools/aapt2/link/FeatureFlagsFilter.h
new file mode 100644
index 0000000..1d342a7
--- /dev/null
+++ b/tools/aapt2/link/FeatureFlagsFilter.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2023 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.
+ */
+
+#pragma once
+
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <utility>
+
+#include "android-base/macros.h"
+#include "cmd/Util.h"
+#include "process/IResourceTableConsumer.h"
+
+namespace aapt {
+
+struct FeatureFlagsFilterOptions {
+ // If true, elements whose featureFlag values are false (i.e., disabled feature) will be removed.
+ bool remove_disabled_elements = true;
+
+ // If true, `Consume()` will return false (error) if a flag was found that is not in
+ // `feature_flag_values`.
+ bool fail_on_unrecognized_flags = true;
+
+ // If true, `Consume()` will return false (error) if a flag was found whose value in
+ // `feature_flag_values` is not defined (std::nullopt).
+ bool flags_must_have_value = true;
+};
+
+// Looks for the `android:featureFlag` attribute in each XML element, validates the flag names and
+// values, and removes elements according to the values in `feature_flag_values`. An element will be
+// removed if the flag's given value is FALSE. A "!" before the flag name in the attribute indicates
+// a boolean NOT operation, i.e., an element will be removed if the flag's given value is TRUE. For
+// example, if the XML is the following:
+//
+// <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+// <permission android:name="FOO" android:featureFlag="!flag"
+// android:protectionLevel="normal" />
+// <permission android:name="FOO" android:featureFlag="flag"
+// android:protectionLevel="dangerous" />
+// </manifest>
+//
+// If `feature_flag_values` contains {"flag", true}, then the <permission> element with
+// protectionLevel="normal" will be removed, and the <permission> element with
+// protectionLevel="normal" will be kept.
+//
+// The `Consume()` function will return false if there is an invalid flag found (see
+// FeatureFlagsFilterOptions for customizing the filter's validation behavior). Do not use the XML
+// further if there are errors as there may be elements removed already.
+class FeatureFlagsFilter : public IXmlResourceConsumer {
+ public:
+ explicit FeatureFlagsFilter(FeatureFlagValues feature_flag_values,
+ FeatureFlagsFilterOptions options)
+ : feature_flag_values_(std::move(feature_flag_values)), options_(options) {
+ }
+
+ bool Consume(IAaptContext* context, xml::XmlResource* doc) override;
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(FeatureFlagsFilter);
+
+ const FeatureFlagValues feature_flag_values_;
+ const FeatureFlagsFilterOptions options_;
+};
+
+} // namespace aapt
diff --git a/tools/aapt2/link/FeatureFlagsFilter_test.cpp b/tools/aapt2/link/FeatureFlagsFilter_test.cpp
new file mode 100644
index 0000000..53086cc
--- /dev/null
+++ b/tools/aapt2/link/FeatureFlagsFilter_test.cpp
@@ -0,0 +1,236 @@
+/*
+ * Copyright 2023 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/FeatureFlagsFilter.h"
+
+#include <string_view>
+
+#include "test/Test.h"
+
+using ::testing::IsNull;
+using ::testing::NotNull;
+
+namespace aapt {
+
+// Returns null if there was an error from FeatureFlagsFilter.
+std::unique_ptr<xml::XmlResource> VerifyWithOptions(std::string_view str,
+ const FeatureFlagValues& feature_flag_values,
+ const FeatureFlagsFilterOptions& options) {
+ std::unique_ptr<xml::XmlResource> doc = test::BuildXmlDom(str);
+ FeatureFlagsFilter filter(feature_flag_values, options);
+ if (filter.Consume(test::ContextBuilder().Build().get(), doc.get())) {
+ return doc;
+ }
+ return {};
+}
+
+// Returns null if there was an error from FeatureFlagsFilter.
+std::unique_ptr<xml::XmlResource> Verify(std::string_view str,
+ const FeatureFlagValues& feature_flag_values) {
+ return VerifyWithOptions(str, feature_flag_values, {});
+}
+
+TEST(FeatureFlagsFilterTest, NoFeatureFlagAttributes) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" />
+ </manifest>)EOF",
+ {{"flag", false}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+TEST(FeatureFlagsFilterTest, RemoveElementWithDisabledFlag) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="flag" />
+ </manifest>)EOF",
+ {{"flag", false}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, RemoveElementWithNegatedEnabledFlag) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="!flag" />
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, KeepElementWithEnabledFlag) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="flag" />
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST(FeatureFlagsFilterTest, SideBySideEnabledAndDisabled) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="!flag"
+ android:protectionLevel="normal" />
+ <permission android:name="FOO" android:featureFlag="flag"
+ android:protectionLevel="dangerous" />
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto children = root->GetChildElements();
+ ASSERT_EQ(children.size(), 1);
+ auto attr = children[0]->FindAttribute(xml::kSchemaAndroid, "protectionLevel");
+ ASSERT_THAT(attr, NotNull());
+ ASSERT_EQ(attr->value, "dangerous");
+}
+
+TEST(FeatureFlagsFilterTest, RemoveDeeplyNestedElement) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <application>
+ <provider />
+ <activity>
+ <layout android:featureFlag="!flag" />
+ </activity>
+ </application>
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto application = root->FindChild({}, "application");
+ ASSERT_THAT(application, NotNull());
+ auto activity = application->FindChild({}, "activity");
+ ASSERT_THAT(activity, NotNull());
+ auto maybe_removed = activity->FindChild({}, "layout");
+ ASSERT_THAT(maybe_removed, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, KeepDeeplyNestedElement) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <application>
+ <provider />
+ <activity>
+ <layout android:featureFlag="flag" />
+ </activity>
+ </application>
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto application = root->FindChild({}, "application");
+ ASSERT_THAT(application, NotNull());
+ auto activity = application->FindChild({}, "activity");
+ ASSERT_THAT(activity, NotNull());
+ auto maybe_removed = activity->FindChild({}, "layout");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST(FeatureFlagsFilterTest, FailOnEmptyFeatureFlagAttribute) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag=" " />
+ </manifest>)EOF",
+ {{"flag", false}});
+ ASSERT_THAT(doc, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, FailOnFlagWithNoGivenValue) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="flag" />
+ </manifest>)EOF",
+ {{"flag", std::nullopt}});
+ ASSERT_THAT(doc, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, FailOnUnrecognizedFlag) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="unrecognized" />
+ </manifest>)EOF",
+ {{"flag", true}});
+ ASSERT_THAT(doc, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, FailOnMultipleValidationErrors) {
+ auto doc = Verify(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="bar" />
+ <permission android:name="FOO" android:featureFlag="unrecognized" />
+ </manifest>)EOF",
+ {{"flag", std::nullopt}});
+ ASSERT_THAT(doc, IsNull());
+}
+
+TEST(FeatureFlagsFilterTest, OptionRemoveDisabledElementsIsFalse) {
+ auto doc = VerifyWithOptions(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="flag" />
+ </manifest>)EOF",
+ {{"flag", false}}, {.remove_disabled_elements = false});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST(FeatureFlagsFilterTest, OptionFlagsMustHaveValueIsFalse) {
+ auto doc = VerifyWithOptions(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="flag" />
+ </manifest>)EOF",
+ {{"flag", std::nullopt}}, {.flags_must_have_value = false});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+
+TEST(FeatureFlagsFilterTest, OptionFailOnUnrecognizedFlagsIsFalse) {
+ auto doc = VerifyWithOptions(R"EOF(
+ <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="android">
+ <permission android:name="FOO" android:featureFlag="unrecognized" />
+ </manifest>)EOF",
+ {{"flag", true}}, {.fail_on_unrecognized_flags = false});
+ ASSERT_THAT(doc, NotNull());
+ auto root = doc->root.get();
+ ASSERT_THAT(root, NotNull());
+ auto maybe_removed = root->FindChild({}, "permission");
+ ASSERT_THAT(maybe_removed, NotNull());
+}
+
+} // namespace aapt