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.h b/tools/aapt2/link/XmlCompatVersioner.h
new file mode 100644
index 0000000..099e23c
--- /dev/null
+++ b/tools/aapt2/link/XmlCompatVersioner.h
@@ -0,0 +1,100 @@
+/*
+ * 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.
+ */
+
+#ifndef AAPT_LINKER_XMLCOMPATVERSIONER_H
+#define AAPT_LINKER_XMLCOMPATVERSIONER_H
+
+#include <set>
+#include <unordered_map>
+#include <vector>
+
+#include "android-base/macros.h"
+
+#include "Resource.h"
+#include "SdkConstants.h"
+#include "process/IResourceTableConsumer.h"
+#include "util/Util.h"
+#include "xml/XmlDom.h"
+
+namespace aapt {
+
+class IDegradeRule;
+
+struct DegradeResult {
+ xml::Attribute attr;
+ ApiVersion attr_api_version;
+};
+
+class IDegradeRule {
+ public:
+ IDegradeRule() = default;
+ virtual ~IDegradeRule() = default;
+
+ virtual std::vector<DegradeResult> Degrade(const xml::Element& src_el,
+ const xml::Attribute& src_attr,
+ StringPool* out_string_pool) const = 0;
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(IDegradeRule);
+};
+
+class XmlCompatVersioner {
+ public:
+ using Rules = std::unordered_map<ResourceId, std::unique_ptr<IDegradeRule>>;
+
+ XmlCompatVersioner(const Rules* rules);
+
+ std::vector<std::unique_ptr<xml::XmlResource>> Process(IAaptContext* context,
+ xml::XmlResource* doc,
+ util::Range<ApiVersion> api_range);
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(XmlCompatVersioner);
+
+ std::unique_ptr<xml::XmlResource> ProcessDoc(ApiVersion target_api, ApiVersion max_api,
+ xml::XmlResource* doc,
+ std::set<ApiVersion>* out_apis_referenced);
+ void 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);
+
+ const Rules* rules_;
+};
+
+struct ReplacementAttr {
+ std::string name;
+ ResourceId id;
+ Attribute attr;
+};
+
+class DegradeToManyRule : public IDegradeRule {
+ public:
+ DegradeToManyRule(std::vector<ReplacementAttr> attrs);
+ virtual ~DegradeToManyRule() = default;
+
+ std::vector<DegradeResult> Degrade(const xml::Element& src_el, const xml::Attribute& src_attr,
+ StringPool* out_string_pool) const override;
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(DegradeToManyRule);
+
+ std::vector<ReplacementAttr> attrs_;
+};
+
+} // namespace aapt
+
+#endif // AAPT_LINKER_XMLCOMPATVERSIONER_H