tools/aapt2/ResourceParser.cpp

/*
 * Copyright (C) 2015 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 "ResourceParser.h"

#include <functional>
#include <sstream>

#include "android-base/logging.h"

#include "ResourceTable.h"
#include "ResourceUtils.h"
#include "ResourceValues.h"
#include "ValueVisitor.h"
#include "util/ImmutableMap.h"
#include "util/Maybe.h"
#include "util/Util.h"
#include "xml/XmlPullParser.h"

using android::StringPiece;

namespace aapt {

constexpr const char* sXliffNamespaceUri =
    "urn:oasis:names:tc:xliff:document:1.2";

/**
 * Returns true if the element is <skip> or <eat-comment> and can be safely
 * ignored.
 */
static bool ShouldIgnoreElement(const StringPiece& ns,
                                const StringPiece& name) {
  return ns.empty() && (name == "skip" || name == "eat-comment");
}

static uint32_t ParseFormatType(const StringPiece& piece) {
  if (piece == "reference")
    return android::ResTable_map::TYPE_REFERENCE;
  else if (piece == "string")
    return android::ResTable_map::TYPE_STRING;
  else if (piece == "integer")
    return android::ResTable_map::TYPE_INTEGER;
  else if (piece == "boolean")
    return android::ResTable_map::TYPE_BOOLEAN;
  else if (piece == "color")
    return android::ResTable_map::TYPE_COLOR;
  else if (piece == "float")
    return android::ResTable_map::TYPE_FLOAT;
  else if (piece == "dimension")
    return android::ResTable_map::TYPE_DIMENSION;
  else if (piece == "fraction")
    return android::ResTable_map::TYPE_FRACTION;
  else if (piece == "enum")
    return android::ResTable_map::TYPE_ENUM;
  else if (piece == "flags")
    return android::ResTable_map::TYPE_FLAGS;
  return 0;
}

static uint32_t ParseFormatAttribute(const StringPiece& str) {
  uint32_t mask = 0;
  for (StringPiece part : util::Tokenize(str, '|')) {
    StringPiece trimmed_part = util::TrimWhitespace(part);
    uint32_t type = ParseFormatType(trimmed_part);
    if (type == 0) {
      return 0;
    }
    mask |= type;
  }
  return mask;
}

/**
 * A parsed resource ready to be added to the ResourceTable.
 */
struct ParsedResource {
  ResourceName name;
  ConfigDescription config;
  std::string product;
  Source source;
  ResourceId id;
  Maybe<SymbolState> symbol_state;
  std::string comment;
  std::unique_ptr<Value> value;
  std::list<ParsedResource> child_resources;
};

// Recursively adds resources to the ResourceTable.
static bool AddResourcesToTable(ResourceTable* table, IDiagnostics* diag,
                                ParsedResource* res) {
  StringPiece trimmed_comment = util::TrimWhitespace(res->comment);
  if (trimmed_comment.size() != res->comment.size()) {
    // Only if there was a change do we re-assign.
    res->comment = trimmed_comment.to_string();
  }

  if (res->symbol_state) {
    Symbol symbol;
    symbol.state = res->symbol_state.value();
    symbol.source = res->source;
    symbol.comment = res->comment;
    if (!table->SetSymbolState(res->name, res->id, symbol, diag)) {
      return false;
    }
  }

  if (res->value) {
    // Attach the comment, source and config to the value.
    res->value->SetComment(std::move(res->comment));
    res->value->SetSource(std::move(res->source));

    if (!table->AddResource(res->name, res->id, res->config, res->product,
                            std::move(res->value), diag)) {
      return false;
    }
  }

  bool error = false;
  for (ParsedResource& child : res->child_resources) {
    error |= !AddResourcesToTable(table, diag, &child);
  }
  return !error;
}

// Convenient aliases for more readable function calls.
enum { kAllowRawString = true, kNoRawString = false };

ResourceParser::ResourceParser(IDiagnostics* diag, ResourceTable* table,
                               const Source& source,
                               const ConfigDescription& config,
                               const ResourceParserOptions& options)
    : diag_(diag),
      table_(table),
      source_(source),
      config_(config),
      options_(options) {}

/**
 * Build a string from XML that converts nested elements into Span objects.
 */
bool ResourceParser::FlattenXmlSubtree(
    xml::XmlPullParser* parser, std::string* out_raw_string, StyleString* out_style_string,
    std::vector<UntranslatableSection>* out_untranslatable_sections) {
  // Keeps track of formatting tags (<b>, <i>) and the range of characters for which they apply.
  // The stack elements refer to the indices in out_style_string->spans.
  // By first adding to the out_style_string->spans vector, and then using the stack to refer
  // to this vector, the original order of tags is preserved in cases such as <b><i>hello</b></i>.
  std::vector<size_t> span_stack;

  // Clear the output variables.
  out_raw_string->clear();
  out_style_string->spans.clear();
  out_untranslatable_sections->clear();

  // The StringBuilder will concatenate the various segments of text which are initially
  // separated by tags. It also handles unicode escape codes and quotations.
  util::StringBuilder builder;

  // The first occurrence of a <xliff:g> tag. Nested <xliff:g> tags are illegal.
  Maybe<size_t> untranslatable_start_depth;

  size_t depth = 1;
  while (xml::XmlPullParser::IsGoodEvent(parser->Next())) {
    const xml::XmlPullParser::Event event = parser->event();

    if (event == xml::XmlPullParser::Event::kStartElement) {
      if (parser->element_namespace().empty()) {
        // This is an HTML tag which we encode as a span. Add it to the span stack.
        std::string span_name = parser->element_name();
        const auto end_attr_iter = parser->end_attributes();
        for (auto attr_iter = parser->begin_attributes(); attr_iter != end_attr_iter; ++attr_iter) {
          span_name += ";";
          span_name += attr_iter->name;
          span_name += "=";
          span_name += attr_iter->value;
        }

        // Make sure the string is representable in our binary format.
        if (builder.Utf16Len() > std::numeric_limits<uint32_t>::max()) {
          diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                       << "style string '" << builder.ToString() << "' is too long");
          return false;
        }

        out_style_string->spans.push_back(
            Span{std::move(span_name), static_cast<uint32_t>(builder.Utf16Len())});
        span_stack.push_back(out_style_string->spans.size() - 1);
      } else if (parser->element_namespace() == sXliffNamespaceUri) {
        if (parser->element_name() == "g") {
          if (untranslatable_start_depth) {
            // We've already encountered an <xliff:g> tag, and nested <xliff:g> tags are illegal.
            diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                         << "illegal nested XLIFF 'g' tag");
            return false;
          } else {
            // Mark the start of an untranslatable section. Use UTF8 indices/lengths.
            untranslatable_start_depth = depth;
            const size_t current_idx = builder.ToString().size();
            out_untranslatable_sections->push_back(UntranslatableSection{current_idx, current_idx});
          }
        }
        // Ignore other xliff tags, they get handled by other tools.

      } else {
        // Besides XLIFF, any other namespaced tag is unsupported and ignored.
        diag_->Warn(DiagMessage(source_.WithLine(parser->line_number()))
                    << "ignoring element '" << parser->element_name()
                    << "' with unknown namespace '" << parser->element_namespace() << "'");
      }

      // Enter one level inside the element.
      depth++;
    } else if (event == xml::XmlPullParser::Event::kText) {
      // Record both the raw text and append to the builder to deal with escape sequences
      // and quotations.
      out_raw_string->append(parser->text());
      builder.Append(parser->text());
    } else if (event == xml::XmlPullParser::Event::kEndElement) {
      // Return one level from within the element.
      depth--;
      if (depth == 0) {
        break;
      }

      if (parser->element_namespace().empty()) {
        // This is an HTML tag which we encode as a span. Update the span
        // stack and pop the top entry.
        Span& top_span = out_style_string->spans[span_stack.back()];
        top_span.last_char = builder.Utf16Len() - 1;
        span_stack.pop_back();
      } else if (untranslatable_start_depth == make_value(depth)) {
        // This is the end of an untranslatable section. Use UTF8 indices/lengths.
        UntranslatableSection& untranslatable_section = out_untranslatable_sections->back();
        untranslatable_section.end = builder.ToString().size();
        untranslatable_start_depth = {};
      }
    } else if (event == xml::XmlPullParser::Event::kComment) {
      // Ignore.
    } else {
      LOG(FATAL) << "unhandled XML event";
    }
  }

  CHECK(span_stack.empty()) << "spans haven't been fully processed";
  out_style_string->str = builder.ToString();
  return true;
}

bool ResourceParser::Parse(xml::XmlPullParser* parser) {
  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip comments and text.
      continue;
    }

    if (!parser->element_namespace().empty() ||
        parser->element_name() != "resources") {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "root element must be <resources>");
      return false;
    }

    error |= !ParseResources(parser);
    break;
  };

  if (parser->event() == xml::XmlPullParser::Event::kBadDocument) {
    diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                 << "xml parser error: " << parser->error());
    return false;
  }
  return !error;
}

bool ResourceParser::ParseResources(xml::XmlPullParser* parser) {
  std::set<ResourceName> stripped_resources;

  bool error = false;
  std::string comment;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    const xml::XmlPullParser::Event event = parser->event();
    if (event == xml::XmlPullParser::Event::kComment) {
      comment = parser->comment();
      continue;
    }

    if (event == xml::XmlPullParser::Event::kText) {
      if (!util::TrimWhitespace(parser->text()).empty()) {
        diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                     << "plain text not allowed here");
        error = true;
      }
      continue;
    }

    CHECK(event == xml::XmlPullParser::Event::kStartElement);

    if (!parser->element_namespace().empty()) {
      // Skip unknown namespace.
      continue;
    }

    std::string element_name = parser->element_name();
    if (element_name == "skip" || element_name == "eat-comment") {
      comment = "";
      continue;
    }

    ParsedResource parsed_resource;
    parsed_resource.config = config_;
    parsed_resource.source = source_.WithLine(parser->line_number());
    parsed_resource.comment = std::move(comment);

    // Extract the product name if it exists.
    if (Maybe<StringPiece> maybe_product =
            xml::FindNonEmptyAttribute(parser, "product")) {
      parsed_resource.product = maybe_product.value().to_string();
    }

    // Parse the resource regardless of product.
    if (!ParseResource(parser, &parsed_resource)) {
      error = true;
      continue;
    }

    if (!AddResourcesToTable(table_, diag_, &parsed_resource)) {
      error = true;
    }
  }

  // Check that we included at least one variant of each stripped resource.
  for (const ResourceName& stripped_resource : stripped_resources) {
    if (!table_->FindResource(stripped_resource)) {
      // Failed to find the resource.
      diag_->Error(DiagMessage(source_)
                   << "resource '" << stripped_resource
                   << "' "
                      "was filtered out but no product variant remains");
      error = true;
    }
  }

  return !error;
}

bool ResourceParser::ParseResource(xml::XmlPullParser* parser,
                                   ParsedResource* out_resource) {
  struct ItemTypeFormat {
    ResourceType type;
    uint32_t format;
  };

  using BagParseFunc = std::function<bool(ResourceParser*, xml::XmlPullParser*,
                                          ParsedResource*)>;

  static const auto elToItemMap = ImmutableMap<std::string, ItemTypeFormat>::CreatePreSorted({
      {"bool", {ResourceType::kBool, android::ResTable_map::TYPE_BOOLEAN}},
      {"color", {ResourceType::kColor, android::ResTable_map::TYPE_COLOR}},
      {"configVarying", {ResourceType::kConfigVarying, android::ResTable_map::TYPE_ANY}},
      {"dimen",
       {ResourceType::kDimen,
        android::ResTable_map::TYPE_FLOAT | android::ResTable_map::TYPE_FRACTION |
            android::ResTable_map::TYPE_DIMENSION}},
      {"drawable", {ResourceType::kDrawable, android::ResTable_map::TYPE_COLOR}},
      {"fraction",
       {ResourceType::kFraction,
        android::ResTable_map::TYPE_FLOAT | android::ResTable_map::TYPE_FRACTION |
            android::ResTable_map::TYPE_DIMENSION}},
      {"integer", {ResourceType::kInteger, android::ResTable_map::TYPE_INTEGER}},
      {"string", {ResourceType::kString, android::ResTable_map::TYPE_STRING}},
  });

  static const auto elToBagMap = ImmutableMap<std::string, BagParseFunc>::CreatePreSorted({
      {"add-resource", std::mem_fn(&ResourceParser::ParseAddResource)},
      {"array", std::mem_fn(&ResourceParser::ParseArray)},
      {"attr", std::mem_fn(&ResourceParser::ParseAttr)},
      {"configVarying",
       std::bind(&ResourceParser::ParseStyle, std::placeholders::_1, ResourceType::kConfigVarying,
                 std::placeholders::_2, std::placeholders::_3)},
      {"declare-styleable", std::mem_fn(&ResourceParser::ParseDeclareStyleable)},
      {"integer-array", std::mem_fn(&ResourceParser::ParseIntegerArray)},
      {"java-symbol", std::mem_fn(&ResourceParser::ParseSymbol)},
      {"plurals", std::mem_fn(&ResourceParser::ParsePlural)},
      {"public", std::mem_fn(&ResourceParser::ParsePublic)},
      {"public-group", std::mem_fn(&ResourceParser::ParsePublicGroup)},
      {"string-array", std::mem_fn(&ResourceParser::ParseStringArray)},
      {"style", std::bind(&ResourceParser::ParseStyle, std::placeholders::_1, ResourceType::kStyle,
                          std::placeholders::_2, std::placeholders::_3)},
      {"symbol", std::mem_fn(&ResourceParser::ParseSymbol)},
  });

  std::string resource_type = parser->element_name();

  // The value format accepted for this resource.
  uint32_t resource_format = 0u;

  bool can_be_item = true;
  bool can_be_bag = true;
  if (resource_type == "item") {
    can_be_bag = false;

    // Items have their type encoded in the type attribute.
    if (Maybe<StringPiece> maybe_type =
            xml::FindNonEmptyAttribute(parser, "type")) {
      resource_type = maybe_type.value().to_string();
    } else {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "<item> must have a 'type' attribute");
      return false;
    }

    if (Maybe<StringPiece> maybe_format =
            xml::FindNonEmptyAttribute(parser, "format")) {
      // An explicit format for this resource was specified. The resource will
      // retain
      // its type in its name, but the accepted value for this type is
      // overridden.
      resource_format = ParseFormatType(maybe_format.value());
      if (!resource_format) {
        diag_->Error(DiagMessage(out_resource->source)
                     << "'" << maybe_format.value()
                     << "' is an invalid format");
        return false;
      }
    }
  } else if (resource_type == "bag") {
    can_be_item = false;

    // Bags have their type encoded in the type attribute.
    if (Maybe<StringPiece> maybe_type = xml::FindNonEmptyAttribute(parser, "type")) {
      resource_type = maybe_type.value().to_string();
    } else {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "<bag> must have a 'type' attribute");
      return false;
    }
  }

  // Get the name of the resource. This will be checked later, because not all
  // XML elements require a name.
  Maybe<StringPiece> maybe_name = xml::FindNonEmptyAttribute(parser, "name");

  if (resource_type == "id") {
    if (!maybe_name) {
      diag_->Error(DiagMessage(out_resource->source)
                   << "<" << parser->element_name()
                   << "> missing 'name' attribute");
      return false;
    }

    out_resource->name.type = ResourceType::kId;
    out_resource->name.entry = maybe_name.value().to_string();
    out_resource->value = util::make_unique<Id>();
    return true;
  }

  if (can_be_item) {
    const auto item_iter = elToItemMap.find(resource_type);
    if (item_iter != elToItemMap.end()) {
      // This is an item, record its type and format and start parsing.

      if (!maybe_name) {
        diag_->Error(DiagMessage(out_resource->source)
                     << "<" << parser->element_name() << "> missing 'name' attribute");
        return false;
      }

      out_resource->name.type = item_iter->second.type;
      out_resource->name.entry = maybe_name.value().to_string();

      // Only use the implicit format for this type if it wasn't overridden.
      if (!resource_format) {
        resource_format = item_iter->second.format;
      }

      if (!ParseItem(parser, out_resource, resource_format)) {
        return false;
      }
      return true;
    }
  }

  // This might be a bag or something.
  if (can_be_bag) {
    const auto bag_iter = elToBagMap.find(resource_type);
    if (bag_iter != elToBagMap.end()) {
      // Ensure we have a name (unless this is a <public-group>).
      if (resource_type != "public-group") {
        if (!maybe_name) {
          diag_->Error(DiagMessage(out_resource->source)
                       << "<" << parser->element_name() << "> missing 'name' attribute");
          return false;
        }

        out_resource->name.entry = maybe_name.value().to_string();
      }

      // Call the associated parse method. The type will be filled in by the
      // parse func.
      if (!bag_iter->second(this, parser, out_resource)) {
        return false;
      }
      return true;
    }
  }

  if (can_be_item) {
    // Try parsing the elementName (or type) as a resource. These shall only be
    // resources like 'layout' or 'xml' and they can only be references.
    const ResourceType* parsed_type = ParseResourceType(resource_type);
    if (parsed_type) {
      if (!maybe_name) {
        diag_->Error(DiagMessage(out_resource->source)
                     << "<" << parser->element_name()
                     << "> missing 'name' attribute");
        return false;
      }

      out_resource->name.type = *parsed_type;
      out_resource->name.entry = maybe_name.value().to_string();
      out_resource->value = ParseXml(parser, android::ResTable_map::TYPE_REFERENCE, kNoRawString);
      if (!out_resource->value) {
        diag_->Error(DiagMessage(out_resource->source)
                     << "invalid value for type '" << *parsed_type << "'. Expected a reference");
        return false;
      }
      return true;
    }
  }

  diag_->Warn(DiagMessage(out_resource->source)
              << "unknown resource type '" << parser->element_name() << "'");
  return false;
}

bool ResourceParser::ParseItem(xml::XmlPullParser* parser,
                               ParsedResource* out_resource,
                               const uint32_t format) {
  if (format == android::ResTable_map::TYPE_STRING) {
    return ParseString(parser, out_resource);
  }

  out_resource->value = ParseXml(parser, format, kNoRawString);
  if (!out_resource->value) {
    diag_->Error(DiagMessage(out_resource->source) << "invalid "
                                                   << out_resource->name.type);
    return false;
  }
  return true;
}

/**
 * Reads the entire XML subtree and attempts to parse it as some Item,
 * with typeMask denoting which items it can be. If allowRawValue is
 * true, a RawString is returned if the XML couldn't be parsed as
 * an Item. If allowRawValue is false, nullptr is returned in this
 * case.
 */
std::unique_ptr<Item> ResourceParser::ParseXml(xml::XmlPullParser* parser,
                                               const uint32_t type_mask,
                                               const bool allow_raw_value) {
  const size_t begin_xml_line = parser->line_number();

  std::string raw_value;
  StyleString style_string;
  std::vector<UntranslatableSection> untranslatable_sections;
  if (!FlattenXmlSubtree(parser, &raw_value, &style_string, &untranslatable_sections)) {
    return {};
  }

  if (!style_string.spans.empty()) {
    // This can only be a StyledString.
    std::unique_ptr<StyledString> styled_string =
        util::make_unique<StyledString>(table_->string_pool.MakeRef(
            style_string, StringPool::Context(StringPool::Context::kStylePriority, config_)));
    styled_string->untranslatable_sections = std::move(untranslatable_sections);
    return std::move(styled_string);
  }

  auto on_create_reference = [&](const ResourceName& name) {
    // name.package can be empty here, as it will assume the package name of the
    // table.
    std::unique_ptr<Id> id = util::make_unique<Id>();
    id->SetSource(source_.WithLine(begin_xml_line));
    table_->AddResource(name, {}, {}, std::move(id), diag_);
  };

  // Process the raw value.
  std::unique_ptr<Item> processed_item =
      ResourceUtils::TryParseItemForAttribute(raw_value, type_mask,
                                              on_create_reference);
  if (processed_item) {
    // Fix up the reference.
    if (Reference* ref = ValueCast<Reference>(processed_item.get())) {
      TransformReferenceFromNamespace(parser, "", ref);
    }
    return processed_item;
  }

  // Try making a regular string.
  if (type_mask & android::ResTable_map::TYPE_STRING) {
    // Use the trimmed, escaped string.
    std::unique_ptr<String> string = util::make_unique<String>(
        table_->string_pool.MakeRef(style_string.str, StringPool::Context(config_)));
    string->untranslatable_sections = std::move(untranslatable_sections);
    return std::move(string);
  }

  if (allow_raw_value) {
    // We can't parse this so return a RawString if we are allowed.
    return util::make_unique<RawString>(
        table_->string_pool.MakeRef(raw_value, StringPool::Context(config_)));
  }
  return {};
}

bool ResourceParser::ParseString(xml::XmlPullParser* parser,
                                 ParsedResource* out_resource) {
  bool formatted = true;
  if (Maybe<StringPiece> formatted_attr =
          xml::FindAttribute(parser, "formatted")) {
    Maybe<bool> maybe_formatted =
        ResourceUtils::ParseBool(formatted_attr.value());
    if (!maybe_formatted) {
      diag_->Error(DiagMessage(out_resource->source)
                   << "invalid value for 'formatted'. Must be a boolean");
      return false;
    }
    formatted = maybe_formatted.value();
  }

  bool translatable = options_.translatable;
  if (Maybe<StringPiece> translatable_attr = xml::FindAttribute(parser, "translatable")) {
    Maybe<bool> maybe_translatable = ResourceUtils::ParseBool(translatable_attr.value());
    if (!maybe_translatable) {
      diag_->Error(DiagMessage(out_resource->source)
                   << "invalid value for 'translatable'. Must be a boolean");
      return false;
    }
    translatable = maybe_translatable.value();
  }

  out_resource->value =
      ParseXml(parser, android::ResTable_map::TYPE_STRING, kNoRawString);
  if (!out_resource->value) {
    diag_->Error(DiagMessage(out_resource->source) << "not a valid string");
    return false;
  }

  if (String* string_value = ValueCast<String>(out_resource->value.get())) {
    string_value->SetTranslatable(translatable);

    if (formatted && translatable) {
      if (!util::VerifyJavaStringFormat(*string_value->value)) {
        DiagMessage msg(out_resource->source);
        msg << "multiple substitutions specified in non-positional format; "
               "did you mean to add the formatted=\"false\" attribute?";
        if (options_.error_on_positional_arguments) {
          diag_->Error(msg);
          return false;
        }

        diag_->Warn(msg);
      }
    }

  } else if (StyledString* string_value = ValueCast<StyledString>(out_resource->value.get())) {
    string_value->SetTranslatable(translatable);
  }
  return true;
}

bool ResourceParser::ParsePublic(xml::XmlPullParser* parser,
                                 ParsedResource* out_resource) {
  Maybe<StringPiece> maybe_type = xml::FindNonEmptyAttribute(parser, "type");
  if (!maybe_type) {
    diag_->Error(DiagMessage(out_resource->source)
                 << "<public> must have a 'type' attribute");
    return false;
  }

  const ResourceType* parsed_type = ParseResourceType(maybe_type.value());
  if (!parsed_type) {
    diag_->Error(DiagMessage(out_resource->source) << "invalid resource type '"
                                                   << maybe_type.value()
                                                   << "' in <public>");
    return false;
  }

  out_resource->name.type = *parsed_type;

  if (Maybe<StringPiece> maybe_id_str = xml::FindNonEmptyAttribute(parser, "id")) {
    Maybe<ResourceId> maybe_id = ResourceUtils::ParseResourceId(maybe_id_str.value());
    if (!maybe_id) {
      diag_->Error(DiagMessage(out_resource->source)
                   << "invalid resource ID '" << maybe_id_str.value() << "' in <public>");
      return false;
    }
    out_resource->id = maybe_id.value();
  }

  if (*parsed_type == ResourceType::kId) {
    // An ID marked as public is also the definition of an ID.
    out_resource->value = util::make_unique<Id>();
  }

  out_resource->symbol_state = SymbolState::kPublic;
  return true;
}

bool ResourceParser::ParsePublicGroup(xml::XmlPullParser* parser,
                                      ParsedResource* out_resource) {
  Maybe<StringPiece> maybe_type = xml::FindNonEmptyAttribute(parser, "type");
  if (!maybe_type) {
    diag_->Error(DiagMessage(out_resource->source)
                 << "<public-group> must have a 'type' attribute");
    return false;
  }

  const ResourceType* parsed_type = ParseResourceType(maybe_type.value());
  if (!parsed_type) {
    diag_->Error(DiagMessage(out_resource->source) << "invalid resource type '"
                                                   << maybe_type.value()
                                                   << "' in <public-group>");
    return false;
  }

  Maybe<StringPiece> maybe_id_str =
      xml::FindNonEmptyAttribute(parser, "first-id");
  if (!maybe_id_str) {
    diag_->Error(DiagMessage(out_resource->source)
                 << "<public-group> must have a 'first-id' attribute");
    return false;
  }

  Maybe<ResourceId> maybe_id =
      ResourceUtils::ParseResourceId(maybe_id_str.value());
  if (!maybe_id) {
    diag_->Error(DiagMessage(out_resource->source) << "invalid resource ID '"
                                                   << maybe_id_str.value()
                                                   << "' in <public-group>");
    return false;
  }

  ResourceId next_id = maybe_id.value();

  std::string comment;
  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() == xml::XmlPullParser::Event::kComment) {
      comment = util::TrimWhitespace(parser->comment()).to_string();
      continue;
    } else if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip text.
      continue;
    }

    const Source item_source = source_.WithLine(parser->line_number());
    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace.empty() && element_name == "public") {
      Maybe<StringPiece> maybe_name =
          xml::FindNonEmptyAttribute(parser, "name");
      if (!maybe_name) {
        diag_->Error(DiagMessage(item_source)
                     << "<public> must have a 'name' attribute");
        error = true;
        continue;
      }

      if (xml::FindNonEmptyAttribute(parser, "id")) {
        diag_->Error(DiagMessage(item_source)
                     << "'id' is ignored within <public-group>");
        error = true;
        continue;
      }

      if (xml::FindNonEmptyAttribute(parser, "type")) {
        diag_->Error(DiagMessage(item_source)
                     << "'type' is ignored within <public-group>");
        error = true;
        continue;
      }

      ParsedResource child_resource;
      child_resource.name.type = *parsed_type;
      child_resource.name.entry = maybe_name.value().to_string();
      child_resource.id = next_id;
      child_resource.comment = std::move(comment);
      child_resource.source = item_source;
      child_resource.symbol_state = SymbolState::kPublic;
      out_resource->child_resources.push_back(std::move(child_resource));

      next_id.id += 1;

    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(item_source) << ":" << element_name << ">");
      error = true;
    }
  }
  return !error;
}

bool ResourceParser::ParseSymbolImpl(xml::XmlPullParser* parser,
                                     ParsedResource* out_resource) {
  Maybe<StringPiece> maybe_type = xml::FindNonEmptyAttribute(parser, "type");
  if (!maybe_type) {
    diag_->Error(DiagMessage(out_resource->source)
                 << "<" << parser->element_name()
                 << "> must have a 'type' attribute");
    return false;
  }

  const ResourceType* parsed_type = ParseResourceType(maybe_type.value());
  if (!parsed_type) {
    diag_->Error(DiagMessage(out_resource->source)
                 << "invalid resource type '" << maybe_type.value() << "' in <"
                 << parser->element_name() << ">");
    return false;
  }

  out_resource->name.type = *parsed_type;
  return true;
}

bool ResourceParser::ParseSymbol(xml::XmlPullParser* parser,
                                 ParsedResource* out_resource) {
  if (ParseSymbolImpl(parser, out_resource)) {
    out_resource->symbol_state = SymbolState::kPrivate;
    return true;
  }
  return false;
}

bool ResourceParser::ParseAddResource(xml::XmlPullParser* parser,
                                      ParsedResource* out_resource) {
  if (ParseSymbolImpl(parser, out_resource)) {
    out_resource->symbol_state = SymbolState::kUndefined;
    return true;
  }
  return false;
}

bool ResourceParser::ParseAttr(xml::XmlPullParser* parser,
                               ParsedResource* out_resource) {
  return ParseAttrImpl(parser, out_resource, false);
}

bool ResourceParser::ParseAttrImpl(xml::XmlPullParser* parser,
                                   ParsedResource* out_resource, bool weak) {
  out_resource->name.type = ResourceType::kAttr;

  // Attributes only end up in default configuration.
  if (out_resource->config != ConfigDescription::DefaultConfig()) {
    diag_->Warn(DiagMessage(out_resource->source)
                << "ignoring configuration '" << out_resource->config
                << "' for attribute " << out_resource->name);
    out_resource->config = ConfigDescription::DefaultConfig();
  }

  uint32_t type_mask = 0;

  Maybe<StringPiece> maybe_format = xml::FindAttribute(parser, "format");
  if (maybe_format) {
    type_mask = ParseFormatAttribute(maybe_format.value());
    if (type_mask == 0) {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "invalid attribute format '" << maybe_format.value()
                   << "'");
      return false;
    }
  }

  Maybe<int32_t> maybe_min, maybe_max;

  if (Maybe<StringPiece> maybe_min_str = xml::FindAttribute(parser, "min")) {
    StringPiece min_str = util::TrimWhitespace(maybe_min_str.value());
    if (!min_str.empty()) {
      std::u16string min_str16 = util::Utf8ToUtf16(min_str);
      android::Res_value value;
      if (android::ResTable::stringToInt(min_str16.data(), min_str16.size(),
                                         &value)) {
        maybe_min = static_cast<int32_t>(value.data);
      }
    }

    if (!maybe_min) {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "invalid 'min' value '" << min_str << "'");
      return false;
    }
  }

  if (Maybe<StringPiece> maybe_max_str = xml::FindAttribute(parser, "max")) {
    StringPiece max_str = util::TrimWhitespace(maybe_max_str.value());
    if (!max_str.empty()) {
      std::u16string max_str16 = util::Utf8ToUtf16(max_str);
      android::Res_value value;
      if (android::ResTable::stringToInt(max_str16.data(), max_str16.size(),
                                         &value)) {
        maybe_max = static_cast<int32_t>(value.data);
      }
    }

    if (!maybe_max) {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "invalid 'max' value '" << max_str << "'");
      return false;
    }
  }

  if ((maybe_min || maybe_max) &&
      (type_mask & android::ResTable_map::TYPE_INTEGER) == 0) {
    diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                 << "'min' and 'max' can only be used when format='integer'");
    return false;
  }

  struct SymbolComparator {
    bool operator()(const Attribute::Symbol& a, const Attribute::Symbol& b) {
      return a.symbol.name.value() < b.symbol.name.value();
    }
  };

  std::set<Attribute::Symbol, SymbolComparator> items;

  std::string comment;
  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() == xml::XmlPullParser::Event::kComment) {
      comment = util::TrimWhitespace(parser->comment()).to_string();
      continue;
    } else if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip text.
      continue;
    }

    const Source item_source = source_.WithLine(parser->line_number());
    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace.empty() &&
        (element_name == "flag" || element_name == "enum")) {
      if (element_name == "enum") {
        if (type_mask & android::ResTable_map::TYPE_FLAGS) {
          diag_->Error(DiagMessage(item_source)
                       << "can not define an <enum>; already defined a <flag>");
          error = true;
          continue;
        }
        type_mask |= android::ResTable_map::TYPE_ENUM;

      } else if (element_name == "flag") {
        if (type_mask & android::ResTable_map::TYPE_ENUM) {
          diag_->Error(DiagMessage(item_source)
                       << "can not define a <flag>; already defined an <enum>");
          error = true;
          continue;
        }
        type_mask |= android::ResTable_map::TYPE_FLAGS;
      }

      if (Maybe<Attribute::Symbol> s =
              ParseEnumOrFlagItem(parser, element_name)) {
        Attribute::Symbol& symbol = s.value();
        ParsedResource child_resource;
        child_resource.name = symbol.symbol.name.value();
        child_resource.source = item_source;
        child_resource.value = util::make_unique<Id>();
        out_resource->child_resources.push_back(std::move(child_resource));

        symbol.symbol.SetComment(std::move(comment));
        symbol.symbol.SetSource(item_source);

        auto insert_result = items.insert(std::move(symbol));
        if (!insert_result.second) {
          const Attribute::Symbol& existing_symbol = *insert_result.first;
          diag_->Error(DiagMessage(item_source)
                       << "duplicate symbol '"
                       << existing_symbol.symbol.name.value().entry << "'");

          diag_->Note(DiagMessage(existing_symbol.symbol.GetSource())
                      << "first defined here");
          error = true;
        }
      } else {
        error = true;
      }
    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(item_source) << ":" << element_name << ">");
      error = true;
    }

    comment = {};
  }

  if (error) {
    return false;
  }

  std::unique_ptr<Attribute> attr = util::make_unique<Attribute>(weak);
  attr->symbols = std::vector<Attribute::Symbol>(items.begin(), items.end());
  attr->type_mask =
      type_mask ? type_mask : uint32_t(android::ResTable_map::TYPE_ANY);
  if (maybe_min) {
    attr->min_int = maybe_min.value();
  }

  if (maybe_max) {
    attr->max_int = maybe_max.value();
  }
  out_resource->value = std::move(attr);
  return true;
}

Maybe<Attribute::Symbol> ResourceParser::ParseEnumOrFlagItem(
    xml::XmlPullParser* parser, const StringPiece& tag) {
  const Source source = source_.WithLine(parser->line_number());

  Maybe<StringPiece> maybe_name = xml::FindNonEmptyAttribute(parser, "name");
  if (!maybe_name) {
    diag_->Error(DiagMessage(source) << "no attribute 'name' found for tag <"
                                     << tag << ">");
    return {};
  }

  Maybe<StringPiece> maybe_value = xml::FindNonEmptyAttribute(parser, "value");
  if (!maybe_value) {
    diag_->Error(DiagMessage(source) << "no attribute 'value' found for tag <"
                                     << tag << ">");
    return {};
  }

  std::u16string value16 = util::Utf8ToUtf16(maybe_value.value());
  android::Res_value val;
  if (!android::ResTable::stringToInt(value16.data(), value16.size(), &val)) {
    diag_->Error(DiagMessage(source) << "invalid value '" << maybe_value.value()
                                     << "' for <" << tag
                                     << ">; must be an integer");
    return {};
  }

  return Attribute::Symbol{
      Reference(ResourceNameRef({}, ResourceType::kId, maybe_name.value())),
      val.data};
}

bool ResourceParser::ParseStyleItem(xml::XmlPullParser* parser, Style* style) {
  const Source source = source_.WithLine(parser->line_number());

  Maybe<StringPiece> maybe_name = xml::FindNonEmptyAttribute(parser, "name");
  if (!maybe_name) {
    diag_->Error(DiagMessage(source) << "<item> must have a 'name' attribute");
    return false;
  }

  Maybe<Reference> maybe_key =
      ResourceUtils::ParseXmlAttributeName(maybe_name.value());
  if (!maybe_key) {
    diag_->Error(DiagMessage(source) << "invalid attribute name '"
                                     << maybe_name.value() << "'");
    return false;
  }

  TransformReferenceFromNamespace(parser, "", &maybe_key.value());
  maybe_key.value().SetSource(source);

  std::unique_ptr<Item> value = ParseXml(parser, 0, kAllowRawString);
  if (!value) {
    diag_->Error(DiagMessage(source) << "could not parse style item");
    return false;
  }

  style->entries.push_back(
      Style::Entry{std::move(maybe_key.value()), std::move(value)});
  return true;
}

bool ResourceParser::ParseStyle(const ResourceType type, xml::XmlPullParser* parser,
                                ParsedResource* out_resource) {
  out_resource->name.type = type;

  std::unique_ptr<Style> style = util::make_unique<Style>();

  Maybe<StringPiece> maybe_parent = xml::FindAttribute(parser, "parent");
  if (maybe_parent) {
    // If the parent is empty, we don't have a parent, but we also don't infer
    // either.
    if (!maybe_parent.value().empty()) {
      std::string err_str;
      style->parent = ResourceUtils::ParseStyleParentReference(
          maybe_parent.value(), &err_str);
      if (!style->parent) {
        diag_->Error(DiagMessage(out_resource->source) << err_str);
        return false;
      }

      // Transform the namespace prefix to the actual package name, and mark the
      // reference as
      // private if appropriate.
      TransformReferenceFromNamespace(parser, "", &style->parent.value());
    }

  } else {
    // No parent was specified, so try inferring it from the style name.
    std::string style_name = out_resource->name.entry;
    size_t pos = style_name.find_last_of(u'.');
    if (pos != std::string::npos) {
      style->parent_inferred = true;
      style->parent = Reference(
          ResourceName({}, ResourceType::kStyle, style_name.substr(0, pos)));
    }
  }

  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip text and comments.
      continue;
    }

    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace == "" && element_name == "item") {
      error |= !ParseStyleItem(parser, style.get());

    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << ":" << element_name << ">");
      error = true;
    }
  }

  if (error) {
    return false;
  }

  out_resource->value = std::move(style);
  return true;
}

bool ResourceParser::ParseArray(xml::XmlPullParser* parser,
                                ParsedResource* out_resource) {
  return ParseArrayImpl(parser, out_resource, android::ResTable_map::TYPE_ANY);
}

bool ResourceParser::ParseIntegerArray(xml::XmlPullParser* parser,
                                       ParsedResource* out_resource) {
  return ParseArrayImpl(parser, out_resource,
                        android::ResTable_map::TYPE_INTEGER);
}

bool ResourceParser::ParseStringArray(xml::XmlPullParser* parser,
                                      ParsedResource* out_resource) {
  return ParseArrayImpl(parser, out_resource,
                        android::ResTable_map::TYPE_STRING);
}

bool ResourceParser::ParseArrayImpl(xml::XmlPullParser* parser,
                                    ParsedResource* out_resource,
                                    const uint32_t typeMask) {
  out_resource->name.type = ResourceType::kArray;

  std::unique_ptr<Array> array = util::make_unique<Array>();

  bool translatable = options_.translatable;
  if (Maybe<StringPiece> translatable_attr = xml::FindAttribute(parser, "translatable")) {
    Maybe<bool> maybe_translatable = ResourceUtils::ParseBool(translatable_attr.value());
    if (!maybe_translatable) {
      diag_->Error(DiagMessage(out_resource->source)
                   << "invalid value for 'translatable'. Must be a boolean");
      return false;
    }
    translatable = maybe_translatable.value();
  }
  array->SetTranslatable(translatable);

  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip text and comments.
      continue;
    }

    const Source item_source = source_.WithLine(parser->line_number());
    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace.empty() && element_name == "item") {
      std::unique_ptr<Item> item = ParseXml(parser, typeMask, kNoRawString);
      if (!item) {
        diag_->Error(DiagMessage(item_source) << "could not parse array item");
        error = true;
        continue;
      }
      item->SetSource(item_source);
      array->items.emplace_back(std::move(item));

    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(source_.WithLine(parser->line_number()))
                   << "unknown tag <" << element_namespace << ":"
                   << element_name << ">");
      error = true;
    }
  }

  if (error) {
    return false;
  }

  out_resource->value = std::move(array);
  return true;
}

bool ResourceParser::ParsePlural(xml::XmlPullParser* parser,
                                 ParsedResource* out_resource) {
  out_resource->name.type = ResourceType::kPlurals;

  std::unique_ptr<Plural> plural = util::make_unique<Plural>();

  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Skip text and comments.
      continue;
    }

    const Source item_source = source_.WithLine(parser->line_number());
    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace.empty() && element_name == "item") {
      Maybe<StringPiece> maybe_quantity =
          xml::FindNonEmptyAttribute(parser, "quantity");
      if (!maybe_quantity) {
        diag_->Error(DiagMessage(item_source)
                     << "<item> in <plurals> requires attribute "
                     << "'quantity'");
        error = true;
        continue;
      }

      StringPiece trimmed_quantity =
          util::TrimWhitespace(maybe_quantity.value());
      size_t index = 0;
      if (trimmed_quantity == "zero") {
        index = Plural::Zero;
      } else if (trimmed_quantity == "one") {
        index = Plural::One;
      } else if (trimmed_quantity == "two") {
        index = Plural::Two;
      } else if (trimmed_quantity == "few") {
        index = Plural::Few;
      } else if (trimmed_quantity == "many") {
        index = Plural::Many;
      } else if (trimmed_quantity == "other") {
        index = Plural::Other;
      } else {
        diag_->Error(DiagMessage(item_source)
                     << "<item> in <plural> has invalid value '"
                     << trimmed_quantity << "' for attribute 'quantity'");
        error = true;
        continue;
      }

      if (plural->values[index]) {
        diag_->Error(DiagMessage(item_source) << "duplicate quantity '"
                                              << trimmed_quantity << "'");
        error = true;
        continue;
      }

      if (!(plural->values[index] = ParseXml(
                parser, android::ResTable_map::TYPE_STRING, kNoRawString))) {
        error = true;
      }
      plural->values[index]->SetSource(item_source);

    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(item_source) << "unknown tag <"
                                            << element_namespace << ":"
                                            << element_name << ">");
      error = true;
    }
  }

  if (error) {
    return false;
  }

  out_resource->value = std::move(plural);
  return true;
}

bool ResourceParser::ParseDeclareStyleable(xml::XmlPullParser* parser,
                                           ParsedResource* out_resource) {
  out_resource->name.type = ResourceType::kStyleable;

  // Declare-styleable is kPrivate by default, because it technically only
  // exists in R.java.
  out_resource->symbol_state = SymbolState::kPublic;

  // Declare-styleable only ends up in default config;
  if (out_resource->config != ConfigDescription::DefaultConfig()) {
    diag_->Warn(DiagMessage(out_resource->source)
                << "ignoring configuration '" << out_resource->config
                << "' for styleable " << out_resource->name.entry);
    out_resource->config = ConfigDescription::DefaultConfig();
  }

  std::unique_ptr<Styleable> styleable = util::make_unique<Styleable>();

  std::string comment;
  bool error = false;
  const size_t depth = parser->depth();
  while (xml::XmlPullParser::NextChildNode(parser, depth)) {
    if (parser->event() == xml::XmlPullParser::Event::kComment) {
      comment = util::TrimWhitespace(parser->comment()).to_string();
      continue;
    } else if (parser->event() != xml::XmlPullParser::Event::kStartElement) {
      // Ignore text.
      continue;
    }

    const Source item_source = source_.WithLine(parser->line_number());
    const std::string& element_namespace = parser->element_namespace();
    const std::string& element_name = parser->element_name();
    if (element_namespace.empty() && element_name == "attr") {
      Maybe<StringPiece> maybe_name =
          xml::FindNonEmptyAttribute(parser, "name");
      if (!maybe_name) {
        diag_->Error(DiagMessage(item_source)
                     << "<attr> tag must have a 'name' attribute");
        error = true;
        continue;
      }

      // If this is a declaration, the package name may be in the name. Separate
      // these out.
      // Eg. <attr name="android:text" />
      Maybe<Reference> maybe_ref =
          ResourceUtils::ParseXmlAttributeName(maybe_name.value());
      if (!maybe_ref) {
        diag_->Error(DiagMessage(item_source) << "<attr> tag has invalid name '"
                                              << maybe_name.value() << "'");
        error = true;
        continue;
      }

      Reference& child_ref = maybe_ref.value();
      xml::TransformReferenceFromNamespace(parser, "", &child_ref);

      // Create the ParsedResource that will add the attribute to the table.
      ParsedResource child_resource;
      child_resource.name = child_ref.name.value();
      child_resource.source = item_source;
      child_resource.comment = std::move(comment);

      if (!ParseAttrImpl(parser, &child_resource, true)) {
        error = true;
        continue;
      }

      // Create the reference to this attribute.
      child_ref.SetComment(child_resource.comment);
      child_ref.SetSource(item_source);
      styleable->entries.push_back(std::move(child_ref));

      out_resource->child_resources.push_back(std::move(child_resource));

    } else if (!ShouldIgnoreElement(element_namespace, element_name)) {
      diag_->Error(DiagMessage(item_source) << "unknown tag <"
                                            << element_namespace << ":"
                                            << element_name << ">");
      error = true;
    }

    comment = {};
  }

  if (error) {
    return false;
  }

  out_resource->value = std::move(styleable);
  return true;
}

}  // namespace aapt