Replace Maybe with std::optional

With c++17, std::optional provides the functionality that Maybe
provided.

Bug: 183215655
Test: aapt2_tests
Change-Id: I62bb9c2fa4985dc5217a6ed153df92b85ad9a034
diff --git a/tools/aapt2/link/AutoVersioner.cpp b/tools/aapt2/link/AutoVersioner.cpp
index 876494e..328ac97 100644
--- a/tools/aapt2/link/AutoVersioner.cpp
+++ b/tools/aapt2/link/AutoVersioner.cpp
@@ -90,7 +90,7 @@
           }
 
           if (Style* style = ValueCast<Style>(config_value->value.get())) {
-            Maybe<ApiVersion> min_sdk_stripped;
+            std::optional<ApiVersion> min_sdk_stripped;
             std::vector<Style::Entry> stripped;
 
             auto iter = style->entries.begin();
diff --git a/tools/aapt2/link/AutoVersioner_test.cpp b/tools/aapt2/link/AutoVersioner_test.cpp
index 02fd00b..8179d46 100644
--- a/tools/aapt2/link/AutoVersioner_test.cpp
+++ b/tools/aapt2/link/AutoVersioner_test.cpp
@@ -87,25 +87,27 @@
   Style* style = test::GetValueForConfig<Style>(table.get(), "app:style/Foo", test::ParseConfigOrDie("v4"));
   ASSERT_THAT(style, NotNull());
   ASSERT_EQ(style->entries.size(), 1u);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/onClick")), style->entries.front().key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/onClick"), style->entries.front().key.name);
 
   style = test::GetValueForConfig<Style>(table.get(), "app:style/Foo", test::ParseConfigOrDie("v13"));
   ASSERT_THAT(style, NotNull());
   ASSERT_EQ(style->entries.size(), 2u);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/onClick")),style->entries[0].key.name);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/requiresSmallestWidthDp")), style->entries[1].key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/onClick"), style->entries[0].key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/requiresSmallestWidthDp"),
+            style->entries[1].key.name);
 
   style = test::GetValueForConfig<Style>(table.get(), "app:style/Foo", test::ParseConfigOrDie("v17"));
   ASSERT_THAT(style, NotNull());
   ASSERT_EQ(style->entries.size(), 3u);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/onClick")), style->entries[0].key.name);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/requiresSmallestWidthDp")), style->entries[1].key.name);
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/paddingStart")), style->entries[2].key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/onClick"), style->entries[0].key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/requiresSmallestWidthDp"),
+            style->entries[1].key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/paddingStart"), style->entries[2].key.name);
 
   style = test::GetValueForConfig<Style>(table.get(), "app:style/Foo", test::ParseConfigOrDie("v21"));
   ASSERT_THAT(style, NotNull());
   ASSERT_EQ(1u, style->entries.size());
-  EXPECT_EQ(make_value(test::ParseNameOrDie("android:attr/paddingEnd")), style->entries.front().key.name);
+  EXPECT_EQ(test::ParseNameOrDie("android:attr/paddingEnd"), style->entries.front().key.name);
 }
 
 }  // namespace aapt
diff --git a/tools/aapt2/link/ManifestFixer.cpp b/tools/aapt2/link/ManifestFixer.cpp
index 8abd9de..1bb0696 100644
--- a/tools/aapt2/link/ManifestFixer.cpp
+++ b/tools/aapt2/link/ManifestFixer.cpp
@@ -52,7 +52,7 @@
   // We allow unqualified class names (ie: .HelloActivity)
   // Since we don't know the package name, we can just make a fake one here and
   // the test will be identical as long as the real package name is valid too.
-  Maybe<std::string> fully_qualified_class_name =
+  std::optional<std::string> fully_qualified_class_name =
       util::GetFullyQualifiedClassName("a", attr->value);
 
   StringPiece qualified_class_name = fully_qualified_class_name
@@ -146,7 +146,7 @@
     // Now inject the android:isFeatureSplit="true" attribute.
     xml::Attribute* attr = el->FindAttribute(xml::kSchemaAndroid, kIsFeatureSplit);
     if (attr != nullptr) {
-      if (!ResourceUtils::ParseBool(attr->value).value_or_default(false)) {
+      if (!ResourceUtils::ParseBool(attr->value).value_or(false)) {
         // The isFeatureSplit attribute is false, which conflicts with the use
         // of "featureSplit".
         diag->Error(DiagMessage(el->line_number)
@@ -523,7 +523,8 @@
                                   const StringPiece& attr_name, xml::Element* el) {
   xml::Attribute* attr = el->FindAttribute(attr_ns, attr_name);
   if (attr != nullptr) {
-    if (Maybe<std::string> new_value = util::GetFullyQualifiedClassName(package, attr->value)) {
+    if (std::optional<std::string> new_value =
+            util::GetFullyQualifiedClassName(package, attr->value)) {
       attr->value = std::move(new_value.value());
     }
   }
diff --git a/tools/aapt2/link/ManifestFixer.h b/tools/aapt2/link/ManifestFixer.h
index 34ad8d5..d5d1d17 100644
--- a/tools/aapt2/link/ManifestFixer.h
+++ b/tools/aapt2/link/ManifestFixer.h
@@ -22,7 +22,7 @@
 #include "android-base/macros.h"
 
 #include "process/IResourceTableConsumer.h"
-#include "util/Maybe.h"
+
 #include "xml/XmlActionExecutor.h"
 #include "xml/XmlDom.h"
 
@@ -30,47 +30,47 @@
 
 struct ManifestFixerOptions {
   // The minimum SDK version to set if no 'android:minSdkVersion' is defined in a <uses-sdk> tag.
-  Maybe<std::string> min_sdk_version_default;
+  std::optional<std::string> min_sdk_version_default;
 
   // The target SDK version to set if no 'android:targetSdkVersion' is defined in a <uses-sdk> tag.
-  Maybe<std::string> target_sdk_version_default;
+  std::optional<std::string> target_sdk_version_default;
 
   // The Android package to use instead of the one defined in 'package' in <manifest>.
   // This also renames all relative package/class names in the manifest to fully qualified
   // Java names.
-  Maybe<std::string> rename_manifest_package;
+  std::optional<std::string> rename_manifest_package;
 
   // The Android package to use instead of the one defined in 'android:targetPackage' in
   // <instrumentation>.
-  Maybe<std::string> rename_instrumentation_target_package;
+  std::optional<std::string> rename_instrumentation_target_package;
 
   // The Android package to use instead of the one defined in 'android:targetPackage' in
   // <overlay>.
-  Maybe<std::string> rename_overlay_target_package;
+  std::optional<std::string> rename_overlay_target_package;
 
   // The version name to set if 'android:versionName' is not defined in <manifest> or if
   // replace_version is set.
-  Maybe<std::string> version_name_default;
+  std::optional<std::string> version_name_default;
 
   // The version code to set if 'android:versionCode' is not defined in <manifest> or if
   // replace_version is set.
-  Maybe<std::string> version_code_default;
+  std::optional<std::string> version_code_default;
 
   // The version code to set if 'android:versionCodeMajor' is not defined in <manifest> or if
   // replace_version is set.
-  Maybe<std::string> version_code_major_default;
+  std::optional<std::string> version_code_major_default;
 
   // The revision code to set if 'android:revisionCode' is not defined in <manifest> or if
   // replace_version is set.
-  Maybe<std::string> revision_code_default;
+  std::optional<std::string> revision_code_default;
 
   // The version of the framework being compiled against to set for 'android:compileSdkVersion' in
   // the <manifest> tag.
-  Maybe<std::string> compile_sdk_version;
+  std::optional<std::string> compile_sdk_version;
 
   // The version codename of the framework being compiled against to set for
   // 'android:compileSdkVersionCodename' in the <manifest> tag.
-  Maybe<std::string> compile_sdk_version_codename;
+  std::optional<std::string> compile_sdk_version_codename;
 
   // Whether validation errors should be treated only as warnings. If this is 'true', then an
   // incorrect node will not result in an error, but only as a warning, and the parsing will
diff --git a/tools/aapt2/link/ReferenceLinker.cpp b/tools/aapt2/link/ReferenceLinker.cpp
index 4ac25bd..47c804c 100644
--- a/tools/aapt2/link/ReferenceLinker.cpp
+++ b/tools/aapt2/link/ReferenceLinker.cpp
@@ -190,7 +190,8 @@
  public:
   EmptyDeclStack() = default;
 
-  Maybe<xml::ExtractedPackage> TransformPackageAlias(const StringPiece& alias) const override {
+  std::optional<xml::ExtractedPackage> TransformPackageAlias(
+      const StringPiece& alias) const override {
     if (alias.empty()) {
       return xml::ExtractedPackage{{}, true /*private*/};
     }
@@ -206,7 +207,8 @@
       : alias_namespaces_(std::move(namespaces)) {
   }
 
-  Maybe<xml::ExtractedPackage> TransformPackageAlias(const StringPiece& alias) const override {
+  std::optional<xml::ExtractedPackage> TransformPackageAlias(
+      const StringPiece& alias) const override {
     if (alias.empty()) {
       return xml::ExtractedPackage{{}, true /*private*/};
     }
@@ -322,11 +324,11 @@
   return symbol;
 }
 
-Maybe<xml::AaptAttribute> ReferenceLinker::CompileXmlAttribute(const Reference& reference,
-                                                               const CallSite& callsite,
-                                                               IAaptContext* context,
-                                                               SymbolTable* symbols,
-                                                               std::string* out_error) {
+std::optional<xml::AaptAttribute> ReferenceLinker::CompileXmlAttribute(const Reference& reference,
+                                                                       const CallSite& callsite,
+                                                                       IAaptContext* context,
+                                                                       SymbolTable* symbols,
+                                                                       std::string* out_error) {
   const SymbolTable::Symbol* symbol =
       ResolveAttributeCheckVisibility(reference, callsite, context, symbols, out_error);
   if (!symbol) {
diff --git a/tools/aapt2/link/ReferenceLinker.h b/tools/aapt2/link/ReferenceLinker.h
index 770f1e5..b460853 100644
--- a/tools/aapt2/link/ReferenceLinker.h
+++ b/tools/aapt2/link/ReferenceLinker.h
@@ -97,11 +97,11 @@
 
   // Resolves the attribute reference and returns an xml::AaptAttribute if successful.
   // If resolution fails, outError holds the error message.
-  static Maybe<xml::AaptAttribute> CompileXmlAttribute(const Reference& reference,
-                                                       const CallSite& callsite,
-                                                       IAaptContext* context,
-                                                       SymbolTable* symbols,
-                                                       std::string* out_error);
+  static std::optional<xml::AaptAttribute> CompileXmlAttribute(const Reference& reference,
+                                                               const CallSite& callsite,
+                                                               IAaptContext* context,
+                                                               SymbolTable* symbols,
+                                                               std::string* out_error);
 
   // Writes the resource name to the DiagMessage, using the
   // "orig_name (aka <transformed_name>)" syntax.
diff --git a/tools/aapt2/link/ReferenceLinker_test.cpp b/tools/aapt2/link/ReferenceLinker_test.cpp
index 2d8f0d3..97bdd3e 100644
--- a/tools/aapt2/link/ReferenceLinker_test.cpp
+++ b/tools/aapt2/link/ReferenceLinker_test.cpp
@@ -317,12 +317,12 @@
                                                                 CallSite{"com.app.test"},
                                                                 context.get(), &table);
   ASSERT_THAT(s, NotNull());
-  EXPECT_THAT(s->id, Eq(make_value<ResourceId>(0x7f010000)));
+  EXPECT_THAT(s->id, Eq(0x7f010000));
 
   s = ReferenceLinker::ResolveSymbol(*test::BuildReference("string/foo"), CallSite{"com.app.lib"},
                                      context.get(), &table);
   ASSERT_THAT(s, NotNull());
-  EXPECT_THAT(s->id, Eq(make_value<ResourceId>(0x7f010001)));
+  EXPECT_THAT(s->id, Eq(0x7f010001));
 
   EXPECT_THAT(ReferenceLinker::ResolveSymbol(*test::BuildReference("string/foo"),
                                              CallSite{"com.app.bad"}, context.get(), &table),
@@ -348,7 +348,7 @@
                                                                 CallSite{"com.app.test"},
                                                                 context.get(), &table);
   ASSERT_THAT(s, NotNull());
-  EXPECT_THAT(s->id, Eq(make_value<ResourceId>(0x80010000)));
+  EXPECT_THAT(s->id, Eq(0x80010000));
 
   s = ReferenceLinker::ResolveSymbol(*test::BuildReference("string/foo"), CallSite{"com.app.lib"},
                                      context.get(), &table);
diff --git a/tools/aapt2/link/TableMerger.cpp b/tools/aapt2/link/TableMerger.cpp
index 22f4d18..d094d36 100644
--- a/tools/aapt2/link/TableMerger.cpp
+++ b/tools/aapt2/link/TableMerger.cpp
@@ -303,8 +303,8 @@
           dst_config_value->value = std::move(new_file_ref);
 
         } else {
-          Maybe<std::string> original_comment = (dst_config_value->value)
-              ? dst_config_value->value->GetComment() : Maybe<std::string>();
+          auto original_comment = (dst_config_value->value)
+              ? dst_config_value->value->GetComment() : std::optional<std::string>();
 
           dst_config_value->value = src_config_value->value->Transform(cloner);
 
diff --git a/tools/aapt2/link/TableMerger_test.cpp b/tools/aapt2/link/TableMerger_test.cpp
index 4358fb5..4cbf2d3 100644
--- a/tools/aapt2/link/TableMerger_test.cpp
+++ b/tools/aapt2/link/TableMerger_test.cpp
@@ -409,8 +409,7 @@
 
   const auto expected = ResourceUtils::MakeBool(true);
   EXPECT_THAT(style->entries, Contains(Field(&Style::Entry::value, Pointee(ValueEq(*expected)))));
-  EXPECT_THAT(style->parent,
-              Eq(make_value(Reference(test::ParseNameOrDie("com.app.a:style/OverlayParent")))));
+  EXPECT_THAT(style->parent, Reference(test::ParseNameOrDie("com.app.a:style/OverlayParent")));
 }
 
 TEST_F(TableMergerTest, OverrideStyleInsteadOfOverlaying) {
@@ -483,7 +482,7 @@
   ASSERT_TRUE(merger.Merge({}, table_b.get(), false /*overlay*/));
 
   const ResourceName name = test::ParseNameOrDie("com.app.a:bool/foo");
-  Maybe<ResourceTable::SearchResult> search_result = final_table.FindResource(name);
+  std::optional<ResourceTable::SearchResult> search_result = final_table.FindResource(name);
   ASSERT_TRUE(search_result);
   ASSERT_TRUE(search_result.value().entry->overlayable_item);
   OverlayableItem& result_overlayable_item = search_result.value().entry->overlayable_item.value();
@@ -517,7 +516,7 @@
   ASSERT_TRUE(merger.Merge({}, table_b.get(), false /*overlay*/));
 
   const ResourceName name = test::ParseNameOrDie("com.app.a:bool/foo");
-  Maybe<ResourceTable::SearchResult> search_result = final_table.FindResource(name);
+  std::optional<ResourceTable::SearchResult> search_result = final_table.FindResource(name);
   ASSERT_TRUE(search_result);
   ASSERT_TRUE(search_result.value().entry->overlayable_item);
   OverlayableItem& result_overlayable_item = search_result.value().entry->overlayable_item.value();
diff --git a/tools/aapt2/link/XmlReferenceLinker.cpp b/tools/aapt2/link/XmlReferenceLinker.cpp
index aaa085e..1f8548b 100644
--- a/tools/aapt2/link/XmlReferenceLinker.cpp
+++ b/tools/aapt2/link/XmlReferenceLinker.cpp
@@ -68,7 +68,7 @@
 
       const Attribute* attribute = &default_attribute;
 
-      if (Maybe<xml::ExtractedPackage> maybe_package =
+      if (std::optional<xml::ExtractedPackage> maybe_package =
               xml::ExtractPackageFromNamespace(attr.namespace_uri)) {
         // There is a valid package name for this attribute. We will look this up.
         Reference attr_ref(
diff --git a/tools/aapt2/link/XmlReferenceLinker_test.cpp b/tools/aapt2/link/XmlReferenceLinker_test.cpp
index ddf5b9a..6d96cf1 100644
--- a/tools/aapt2/link/XmlReferenceLinker_test.cpp
+++ b/tools/aapt2/link/XmlReferenceLinker_test.cpp
@@ -100,18 +100,18 @@
   xml::Attribute* xml_attr = view_el->FindAttribute(xml::kSchemaAndroid, "layout_width");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x01010000)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x01010000), xml_attr->compiled_attribute.value().id);
   EXPECT_THAT(ValueCast<BinaryPrimitive>(xml_attr->compiled_value.get()), NotNull());
 
   xml_attr = view_el->FindAttribute(xml::kSchemaAndroid, "background");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x01010001)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x01010001), xml_attr->compiled_attribute.value().id);
   Reference* ref = ValueCast<Reference>(xml_attr->compiled_value.get());
   ASSERT_THAT(ref, NotNull());
-  EXPECT_EQ(make_value(test::ParseNameOrDie("color/green")), ref->name);  // Make sure the name
-                                                                          // didn't change.
-  EXPECT_EQ(make_value(ResourceId(0x7f020000)), ref->id);
+  EXPECT_EQ(test::ParseNameOrDie("color/green"), ref->name);  // Make sure the name
+                                                              // didn't change.
+  EXPECT_EQ(ResourceId(0x7f020000), ref->id);
 
   xml_attr = view_el->FindAttribute(xml::kSchemaAndroid, "text");
   ASSERT_THAT(xml_attr, NotNull());
@@ -172,7 +172,7 @@
       view_el->FindAttribute(xml::BuildPackageNamespace("com.android.support"), "colorAccent");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x7f010001)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x7f010001), xml_attr->compiled_attribute.value().id);
   EXPECT_THAT(ValueCast<BinaryPrimitive>(xml_attr->compiled_value.get()), NotNull());
 }
 
@@ -190,11 +190,11 @@
   xml::Attribute* xml_attr = view_el->FindAttribute(xml::kSchemaAuto, "colorAccent");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x7f010000)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x7f010000), xml_attr->compiled_attribute.value().id);
   Reference* ref = ValueCast<Reference>(xml_attr->compiled_value.get());
   ASSERT_THAT(ref, NotNull());
   ASSERT_TRUE(ref->name);
-  EXPECT_EQ(make_value(ResourceId(0x7f020001)), ref->id);
+  EXPECT_EQ(ResourceId(0x7f020001), ref->id);
 }
 
 TEST_F(XmlReferenceLinkerTest, LinkViewWithShadowedPackageAlias) {
@@ -214,10 +214,10 @@
   xml::Attribute* xml_attr = view_el->FindAttribute(xml::kSchemaAndroid, "attr");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x01010002)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x01010002), xml_attr->compiled_attribute.value().id);
   Reference* ref = ValueCast<Reference>(xml_attr->compiled_value.get());
   ASSERT_THAT(ref, NotNull());
-  EXPECT_EQ(make_value(ResourceId(0x01030000)), ref->id);
+  EXPECT_EQ(ResourceId(0x01030000), ref->id);
 
   ASSERT_FALSE(view_el->GetChildElements().empty());
   view_el = view_el->GetChildElements().front();
@@ -228,10 +228,10 @@
   xml_attr = view_el->FindAttribute(xml::BuildPackageNamespace("com.app.test"), "attr");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x7f010002)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x7f010002), xml_attr->compiled_attribute.value().id);
   ref = ValueCast<Reference>(xml_attr->compiled_value.get());
   ASSERT_THAT(ref, NotNull());
-  EXPECT_EQ(make_value(ResourceId(0x7f030000)), ref->id);
+  EXPECT_EQ(ResourceId(0x7f030000), ref->id);
 }
 
 TEST_F(XmlReferenceLinkerTest, LinkViewWithLocalPackageAndAliasOfTheSameName) {
@@ -250,10 +250,10 @@
   xml::Attribute* xml_attr = view_el->FindAttribute(xml::BuildPackageNamespace("com.app.test"), "attr");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x7f010002)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x7f010002), xml_attr->compiled_attribute.value().id);
   Reference* ref = ValueCast<Reference>(xml_attr->compiled_value.get());
   ASSERT_THAT(ref, NotNull());
-  EXPECT_EQ(make_value(ResourceId(0x7f030000)), ref->id);
+  EXPECT_EQ(ResourceId(0x7f030000), ref->id);
 }
 
 
@@ -270,7 +270,7 @@
   xml::Attribute* xml_attr = gradient_el->FindAttribute(xml::kSchemaAndroid, "angle");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x01010004)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x01010004), xml_attr->compiled_attribute.value().id);
 
   BinaryPrimitive* value = ValueCast<BinaryPrimitive>(xml_attr->compiled_value.get());
   ASSERT_THAT(value, NotNull());
@@ -292,7 +292,7 @@
   xml::Attribute* xml_attr = gradient_el->FindAttribute(xml::kSchemaAndroid, "angle");
   ASSERT_THAT(xml_attr, NotNull());
   ASSERT_TRUE(xml_attr->compiled_attribute);
-  EXPECT_EQ(make_value(ResourceId(0x01010004)), xml_attr->compiled_attribute.value().id);
+  EXPECT_EQ(ResourceId(0x01010004), xml_attr->compiled_attribute.value().id);
 
   BinaryPrimitive* value = ValueCast<BinaryPrimitive>(xml_attr->compiled_value.get());
   ASSERT_THAT(value, NotNull());