AAPT2: Implement attribute compat versioning
This change defines some hardcoded rules to degrade
attributes in newer SDKs to specific older attributes.
An attribute with a degrade rule will generate a new XML for the API
in which the attribute resulting from the degradation was introduced.
Since API 22 (Lollipop MR1), attributes are correctly ignored and do
not need to be versioned. In XML files defined for APIs 22+, the
original and degraded attributes coexist in the same XML file.
One such example is paddingHorizontal, introduced in API 26.
paddingHorizontal degrades to paddingLeft and paddingRight, which
were both introduced in API 1.
Bug: 35763493
Test: make aapt2_tests
Change-Id: I4aa8755a9ee2c0cc5afdc55c3d30093fd3a47f3d
diff --git a/tools/aapt2/link/XmlCompatVersioner.cpp b/tools/aapt2/link/XmlCompatVersioner.cpp
new file mode 100644
index 0000000..f1f4e3b
--- /dev/null
+++ b/tools/aapt2/link/XmlCompatVersioner.cpp
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2017 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/XmlCompatVersioner.h"
+
+#include <algorithm>
+
+#include "util/Util.h"
+
+namespace aapt {
+
+static xml::Attribute CopyAttr(const xml::Attribute& src, StringPool* out_string_pool) {
+ xml::Attribute dst{src.namespace_uri, src.name, src.value, src.compiled_attribute};
+ if (src.compiled_value != nullptr) {
+ dst.compiled_value.reset(src.compiled_value->Clone(out_string_pool));
+ }
+ return dst;
+}
+
+// Returns false if the attribute is not copied because an existing attribute takes precedence
+// (came from a rule).
+static bool CopyAttribute(const xml::Attribute& src_attr, bool generated, xml::Element* dst_el,
+ StringPool* out_string_pool) {
+ xml::Attribute* dst_attr = dst_el->FindAttribute(src_attr.namespace_uri, src_attr.name);
+ if (dst_attr != nullptr) {
+ if (generated) {
+ // Generated attributes always take precedence.
+ dst_attr->value = src_attr.value;
+ dst_attr->compiled_attribute = src_attr.compiled_attribute;
+ if (src_attr.compiled_value != nullptr) {
+ dst_attr->compiled_value.reset(src_attr.compiled_value->Clone(out_string_pool));
+ }
+ return true;
+ }
+ return false;
+ }
+ dst_el->attributes.push_back(CopyAttr(src_attr, out_string_pool));
+ return true;
+}
+
+void XmlCompatVersioner::ProcessRule(const xml::Element& src_el, const xml::Attribute& src_attr,
+ const ApiVersion& src_attr_version, const IDegradeRule* rule,
+ const util::Range<ApiVersion>& api_range, bool generated,
+ xml::Element* dst_el,
+ std::set<ApiVersion>* out_apis_referenced,
+ StringPool* out_string_pool) {
+ if (src_attr_version <= api_range.start) {
+ // The API is compatible, so don't check the rule and just copy.
+ if (!CopyAttribute(src_attr, generated, dst_el, out_string_pool)) {
+ // TODO(adamlesinski): Log a warning that an attribute was overridden?
+ }
+ return;
+ }
+
+ if (api_range.start >= SDK_LOLLIPOP_MR1) {
+ // Since LOLLIPOP MR1, the framework can handle silently ignoring unknown public attributes,
+ // so we don't need to erase/version them.
+ // Copy.
+ if (!CopyAttribute(src_attr, generated, dst_el, out_string_pool)) {
+ // TODO(adamlesinski): Log a warning that an attribute was overridden?
+ }
+ } else {
+ // We are going to erase this attribute from this XML resource version, but check if
+ // we even need to move it anywhere. A developer may have effectively overwritten it with
+ // a similarly versioned XML resource.
+ if (src_attr_version < api_range.end) {
+ // There is room for another versioned XML resource between this XML resource and the next
+ // versioned XML resource defined by the developer.
+ out_apis_referenced->insert(std::min<ApiVersion>(src_attr_version, SDK_LOLLIPOP_MR1));
+ }
+ }
+
+ if (rule != nullptr) {
+ for (const DegradeResult& result : rule->Degrade(src_el, src_attr, out_string_pool)) {
+ const ResourceId attr_resid = result.attr.compiled_attribute.value().id.value();
+ const ApiVersion attr_version = FindAttributeSdkLevel(attr_resid);
+
+ auto iter = rules_->find(attr_resid);
+ ProcessRule(src_el, result.attr, attr_version,
+ iter != rules_->end() ? iter->second.get() : nullptr, api_range,
+ true /*generated*/, dst_el, out_apis_referenced, out_string_pool);
+ }
+ }
+}
+
+XmlCompatVersioner::XmlCompatVersioner(const Rules* rules) : rules_(rules) {
+}
+
+std::unique_ptr<xml::XmlResource> XmlCompatVersioner::ProcessDoc(
+ ApiVersion target_api, ApiVersion max_api, xml::XmlResource* doc,
+ std::set<ApiVersion>* out_apis_referenced) {
+ const util::Range<ApiVersion> api_range{target_api, max_api};
+
+ std::unique_ptr<xml::XmlResource> cloned_doc = util::make_unique<xml::XmlResource>(doc->file);
+ cloned_doc->file.config.sdkVersion = static_cast<uint16_t>(target_api);
+
+ cloned_doc->root = doc->root->Clone([&](const xml::Element& el, xml::Element* out_el) {
+ for (const auto& attr : el.attributes) {
+ if (!attr.compiled_attribute) {
+ // Just copy if this isn't a compiled attribute.
+ out_el->attributes.push_back(CopyAttr(attr, &cloned_doc->string_pool));
+ continue;
+ }
+
+ const ResourceId attr_resid = attr.compiled_attribute.value().id.value();
+ const ApiVersion attr_version = FindAttributeSdkLevel(attr_resid);
+
+ auto rule = rules_->find(attr_resid);
+ ProcessRule(el, attr, attr_version, rule != rules_->end() ? rule->second.get() : nullptr,
+ api_range, false /*generated*/, out_el, out_apis_referenced,
+ &cloned_doc->string_pool);
+ }
+ });
+ return cloned_doc;
+}
+
+std::vector<std::unique_ptr<xml::XmlResource>> XmlCompatVersioner::Process(
+ IAaptContext* context, xml::XmlResource* doc, util::Range<ApiVersion> api_range) {
+ // Adjust the API range so that it falls after this document and after minSdkVersion.
+ api_range.start = std::max(api_range.start, context->GetMinSdkVersion());
+ api_range.start = std::max(api_range.start, static_cast<ApiVersion>(doc->file.config.sdkVersion));
+
+ std::vector<std::unique_ptr<xml::XmlResource>> versioned_docs;
+ std::set<ApiVersion> apis_referenced;
+ versioned_docs.push_back(ProcessDoc(api_range.start, api_range.end, doc, &apis_referenced));
+
+ // Adjust the sdkVersion of the first XML document back to its original (this only really
+ // makes a difference if the sdk version was below the minSdk to start).
+ versioned_docs.back()->file.config.sdkVersion = doc->file.config.sdkVersion;
+
+ // Iterate from smallest to largest API version.
+ for (ApiVersion api : apis_referenced) {
+ std::set<ApiVersion> dummy;
+ versioned_docs.push_back(ProcessDoc(api, api_range.end, doc, &dummy));
+ }
+ return versioned_docs;
+}
+
+DegradeToManyRule::DegradeToManyRule(std::vector<ReplacementAttr> attrs)
+ : attrs_(std::move(attrs)) {
+}
+
+static inline std::unique_ptr<Item> CloneIfNotNull(const std::unique_ptr<Item>& src,
+ StringPool* out_string_pool) {
+ if (src == nullptr) {
+ return {};
+ }
+ return std::unique_ptr<Item>(src->Clone(out_string_pool));
+}
+
+std::vector<DegradeResult> DegradeToManyRule::Degrade(const xml::Element& src_el,
+ const xml::Attribute& src_attr,
+ StringPool* out_string_pool) const {
+ std::vector<DegradeResult> result;
+ result.reserve(attrs_.size());
+ for (const ReplacementAttr& attr : attrs_) {
+ result.push_back(
+ DegradeResult{xml::Attribute{xml::kSchemaAndroid, attr.name, src_attr.value,
+ xml::AaptAttribute{attr.attr, attr.id},
+ CloneIfNotNull(src_attr.compiled_value, out_string_pool)},
+ FindAttributeSdkLevel(attr.id)});
+ }
+ return result;
+}
+
+} // namespace aapt