Base: add Optional<T>.

base/optional_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/optional.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+namespace {
+
+// Object used to test complex object with Optional<T> in addition of the move
+// semantics.
+class TestObject {
+ public:
+  enum class State {
+    DEFAULT_CONSTRUCTED,
+    VALUE_CONSTRUCTED,
+    COPY_CONSTRUCTED,
+    MOVE_CONSTRUCTED,
+    MOVED_FROM,
+  };
+
+  TestObject() : foo_(0), bar_(0.0), state_(State::DEFAULT_CONSTRUCTED) { }
+
+  TestObject(int foo, double bar)
+      : foo_(foo),
+        bar_(bar),
+        state_(State::VALUE_CONSTRUCTED) { }
+
+  TestObject(const TestObject& other)
+      : foo_(other.foo_),
+        bar_(other.bar_),
+        state_(State::COPY_CONSTRUCTED) {
+  }
+
+  TestObject(TestObject&& other)
+      : foo_(std::move(other.foo_)),
+        bar_(std::move(other.bar_)),
+        state_(State::MOVE_CONSTRUCTED) {
+    other.state_ = State::MOVED_FROM;
+  }
+
+  TestObject& operator=(const TestObject& other) {
+    foo_ = other.foo_;
+    bar_ = other.bar_;
+    state_ = State::COPY_CONSTRUCTED;
+    return *this;
+  }
+
+  bool operator==(const TestObject& other) const {
+    return foo_ == other.foo_ && bar_ == other.bar_;
+  }
+
+  int foo() const { return foo_; }
+  State state() const { return state_; }
+
+ private:
+  int foo_;
+  double bar_;
+  State state_;
+};
+
+}  // anonymous namespace
+
+TEST(OptionalTest, DefaultConstructor) {
+  {
+    Optional<float> o;
+    EXPECT_FALSE(o);
+  }
+
+  {
+    Optional<std::string> o;
+    EXPECT_FALSE(o);
+  }
+
+  {
+    Optional<TestObject> o;
+    EXPECT_FALSE(o);
+  }
+}
+
+
+TEST(OptionalTest, ValueConstructor) {
+  {
+    Optional<float> o(0.1f);
+    EXPECT_TRUE(o);
+    EXPECT_EQ(o.value(), 0.1f);
+  }
+
+  {
+    Optional<std::string> o("foo");
+    EXPECT_TRUE(o);
+    EXPECT_EQ(o.value(), "foo");
+  }
+
+  {
+    Optional<TestObject> o(TestObject(3, 0.1));
+    EXPECT_TRUE(o);
+    EXPECT_EQ(o.value(), TestObject(3, 0.1));
+  }
+}
+
+TEST(OptionalTest, CopyConstructor) {
+  {
+    Optional<float> first(0.1f);
+    Optional<float> other(first);
+
+    EXPECT_TRUE(other);
+    EXPECT_EQ(other.value(), 0.1f);
+    EXPECT_EQ(first, other);
+  }
+
+  {
+    Optional<std::string> first("foo");
+    Optional<std::string> other(first);
+
+    EXPECT_TRUE(other);
+    EXPECT_EQ(other.value(), "foo");
+    EXPECT_EQ(first, other);
+  }
+
+  {
+    Optional<TestObject> first(TestObject(3, 0.1));
+    Optional<TestObject> other(first);
+
+    EXPECT_TRUE(other);
+    EXPECT_EQ(other.value(), TestObject(3, 0.1));
+    EXPECT_EQ(first, other);
+  }
+}
+
+TEST(OptionalTest, MoveConstructor) {
+  {
+    Optional<float> first(0.1f);
+    Optional<float> second(std::move(first));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ(second.value(), 0.1f);
+
+    EXPECT_TRUE(first);
+  }
+
+  {
+    Optional<std::string> first("foo");
+    Optional<std::string> second(std::move(first));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ("foo", second.value());
+
+    EXPECT_TRUE(first);
+  }
+
+  {
+    Optional<TestObject> first(TestObject(3, 0.1));
+    Optional<TestObject> second(std::move(first));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ(TestObject::State::MOVE_CONSTRUCTED, second->state());
+    EXPECT_EQ(TestObject(3, 0.1), second.value());
+
+    EXPECT_TRUE(first);
+    EXPECT_EQ(TestObject::State::MOVED_FROM, first->state());
+  }
+}
+
+TEST(OptionalTest, MoveValueConstructor) {
+  {
+    Optional<float> first(0.1f);
+    Optional<float> second(std::move(first.value()));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ(second.value(), 0.1f);
+
+    EXPECT_TRUE(first);
+  }
+
+  {
+    Optional<std::string> first("foo");
+    Optional<std::string> second(std::move(first.value()));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ("foo", second.value());
+
+    EXPECT_TRUE(first);
+  }
+
+  {
+    Optional<TestObject> first(TestObject(3, 0.1));
+    Optional<TestObject> second(std::move(first.value()));
+
+    EXPECT_TRUE(second);
+    EXPECT_EQ(TestObject::State::MOVE_CONSTRUCTED, second->state());
+    EXPECT_EQ(TestObject(3, 0.1), second.value());
+
+    EXPECT_TRUE(first);
+    EXPECT_EQ(TestObject::State::MOVED_FROM, first->state());
+  }
+}
+
+TEST(OptionalTest, ConstructorForwardArguments) {
+  {
+    Optional<float> a(base::in_place, 0.1f);
+    EXPECT_TRUE(a);
+    EXPECT_EQ(0.1f, a.value());
+  }
+
+  {
+    Optional<std::string> a(base::in_place, "foo");
+    EXPECT_TRUE(a);
+    EXPECT_EQ("foo", a.value());
+  }
+
+  {
+    Optional<TestObject> a(base::in_place, 0, 0.1);
+    EXPECT_TRUE(a);
+    EXPECT_EQ(TestObject(0, 0.1), a.value());
+  }
+}
+
+TEST(OptionalTest, Equals) {
+  {
+    Optional<float> a(0.1f);
+    Optional<float> b(0.1f);
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<std::string> a("foo");
+    Optional<std::string> b("foo");
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<TestObject> a(TestObject(3, 0.1));
+    Optional<TestObject> b(TestObject(3, 0.1));
+    EXPECT_EQ(a, b);
+  }
+}
+
+TEST(OptionalTest, EqualsNull) {
+  {
+    Optional<float> a(0.1f);
+    Optional<float> b(0.2f);
+    a = base::nullopt;
+    b = base::nullopt;
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<std::string> a("foo");
+    Optional<std::string> b("bar");
+    a = base::nullopt;
+    b = base::nullopt;
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<TestObject> a(TestObject(3, 0.1));
+    Optional<TestObject> b(TestObject(4, 1.0));
+    a = base::nullopt;
+    b = base::nullopt;
+    EXPECT_EQ(a, b);
+  }
+}
+
+TEST(OptionalTest, NotEquals) {
+  {
+    Optional<float> a(0.1f);
+    Optional<float> b(0.2f);
+    EXPECT_NE(a, b);
+  }
+
+  {
+    Optional<std::string> a("foo");
+    Optional<std::string> b("bar");
+    EXPECT_NE(a, b);
+  }
+
+  {
+    Optional<TestObject> a(TestObject(3, 0.1));
+    Optional<TestObject> b(TestObject(4, 1.0));
+    EXPECT_NE(a, b);
+  }
+}
+
+TEST(OptionalTest, NotEqualsNull) {
+  {
+    Optional<float> a(0.1f);
+    Optional<float> b(0.1f);
+    b = base::nullopt;
+    EXPECT_NE(a, b);
+  }
+
+  {
+    Optional<std::string> a("foo");
+    Optional<std::string> b("foo");
+    b = base::nullopt;
+    EXPECT_NE(a, b);
+  }
+
+  {
+    Optional<TestObject> a(TestObject(3, 0.1));
+    Optional<TestObject> b(TestObject(3, 0.1));
+    b = base::nullopt;
+    EXPECT_NE(a, b);
+  }
+}
+
+TEST(OptionalTest, AssignValue) {
+  {
+    Optional<float> a;
+    EXPECT_FALSE(a);
+    a = 0.1f;
+    EXPECT_TRUE(a);
+
+    Optional<float> b(0.1f);
+    EXPECT_TRUE(a == b);
+  }
+
+  {
+    // Using |const char*| because |std::string| can't be assigned string
+    // literals because of the decay-only perfect forwarding assignment rule.
+    Optional<const char*> a;
+    EXPECT_FALSE(a);
+    a = "foo";
+    EXPECT_TRUE(a);
+
+    Optional<const char*> b("foo");
+    EXPECT_TRUE(a == b);
+  }
+
+  {
+    Optional<TestObject> a;
+    EXPECT_FALSE(a);
+    a = TestObject(3, 0.1);
+    EXPECT_TRUE(a);
+
+    Optional<TestObject> b(TestObject(3, 0.1));
+    EXPECT_TRUE(a == b);
+  }
+}
+
+TEST(OptionalTest, AssignObject) {
+  {
+    Optional<float> a;
+    Optional<float> b(0.1f);
+    a = b;
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ(a.value(), 0.1f);
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<std::string> a;
+    Optional<std::string> b("foo");
+    a = b;
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ(a.value(), "foo");
+    EXPECT_EQ(a, b);
+  }
+
+  {
+    Optional<TestObject> a;
+    Optional<TestObject> b(TestObject(3, 0.1));
+    a = b;
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ(a.value(), TestObject(3, 0.1));
+    EXPECT_EQ(a, b);
+  }
+}
+
+TEST(OptionalTest, AssignObject_rvalue) {
+  {
+    Optional<float> a;
+    Optional<float> b(0.1f);
+    a = std::move(b);
+
+    EXPECT_TRUE(a);
+    EXPECT_TRUE(b);
+    EXPECT_EQ(0.1f, a.value());
+  }
+
+  {
+    Optional<std::string> a;
+    Optional<std::string> b("foo");
+    a = std::move(b);
+
+    EXPECT_TRUE(a);
+    EXPECT_TRUE(b);
+    EXPECT_EQ("foo", a.value());
+  }
+
+  {
+    Optional<TestObject> a;
+    Optional<TestObject> b(TestObject(3, 0.1));
+    a = std::move(b);
+
+    EXPECT_TRUE(a);
+    EXPECT_TRUE(b);
+    EXPECT_EQ(TestObject(3, 0.1), a.value());
+
+    EXPECT_EQ(TestObject::State::MOVE_CONSTRUCTED, a->state());
+    EXPECT_EQ(TestObject::State::MOVED_FROM, b->state());
+  }
+}
+
+TEST(OptionalTest, OperatorStar) {
+  {
+    Optional<float> a(0.1f);
+    EXPECT_EQ(a.value(), *a);
+  }
+
+  {
+    Optional<std::string> a("foo");
+    EXPECT_EQ(a.value(), *a);
+  }
+
+  {
+    Optional<TestObject> a(TestObject(3, 0.1));
+    EXPECT_EQ(a.value(), *a);
+  }
+}
+
+TEST(OptionalTest, OperatorStar_rvalue) {
+  EXPECT_EQ(0.1f, *Optional<float>(0.1f));
+  EXPECT_EQ("foo", *Optional<const char*>("foo"));
+  EXPECT_EQ(TestObject(3, 0.1), *Optional<TestObject>(TestObject(3, 0.1)));
+}
+
+TEST(OptionalTest, OperatorArrow) {
+  Optional<TestObject> a(TestObject(3, 0.1));
+  EXPECT_EQ(a->foo(), 3);
+}
+
+TEST(OptionalTest, Value_rvalue) {
+  EXPECT_EQ(0.1f, Optional<float>(0.1f).value());
+  EXPECT_EQ("foo", Optional<const char*>("foo").value());
+  EXPECT_EQ(TestObject(3, 0.1),
+            Optional<TestObject>(TestObject(3, 0.1)).value());
+}
+
+TEST(OptionalTest, ValueOr) {
+  {
+    Optional<float> a;
+    EXPECT_EQ(0.0f, a.value_or(0.0f));
+
+    a = 0.1f;
+    EXPECT_EQ(0.1f, a.value_or(0.0f));
+
+    a = base::nullopt;
+    EXPECT_EQ(0.0f, a.value_or(0.0f));
+  }
+
+  {
+    // Using |const char*| because |std::string| can't be assigned string
+    // literals because of the decay-only perfect forwarding assignment rule.
+    Optional<const char*> a;
+    EXPECT_EQ("bar", a.value_or("bar"));
+
+    a = "foo";
+    EXPECT_EQ("foo", a.value_or("bar"));
+
+    a = base::nullopt;
+    EXPECT_EQ("bar", a.value_or("bar"));
+  }
+
+  {
+    Optional<TestObject> a;
+    EXPECT_EQ(a.value_or(TestObject(1, 0.3)), TestObject(1, 0.3));
+
+    a = TestObject(3, 0.1);
+    EXPECT_EQ(a.value_or(TestObject(1, 0.3)), TestObject(3, 0.1));
+
+    a = base::nullopt;
+    EXPECT_EQ(a.value_or(TestObject(1, 0.3)), TestObject(1, 0.3));
+  }
+}
+
+TEST(OptionalTest, Swap_bothNoValue) {
+  Optional<TestObject> a, b;
+  a.swap(b);
+
+  EXPECT_FALSE(a);
+  EXPECT_FALSE(b);
+  EXPECT_EQ(TestObject(42, 0.42), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(42, 0.42), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, Swap_inHasValue) {
+  Optional<TestObject> a(TestObject(1, 0.3));
+  Optional<TestObject> b;
+  a.swap(b);
+
+  EXPECT_FALSE(a);
+  EXPECT_TRUE(b);
+  EXPECT_EQ(TestObject(42, 0.42), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(1, 0.3), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, Swap_outHasValue) {
+  Optional<TestObject> a;
+  Optional<TestObject> b(TestObject(1, 0.3));
+  a.swap(b);
+
+  EXPECT_TRUE(a);
+  EXPECT_FALSE(b);
+  EXPECT_EQ(TestObject(1, 0.3), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(42, 0.42), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, Swap_bothValue) {
+  Optional<TestObject> a(TestObject(0, 0.1));
+  Optional<TestObject> b(TestObject(1, 0.3));
+  a.swap(b);
+
+  EXPECT_TRUE(a);
+  EXPECT_TRUE(b);
+  EXPECT_EQ(TestObject(1, 0.3), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(0, 0.1), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, Emplace) {
+  {
+    Optional<float> a(0.1f);
+    a.emplace(0.3f);
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ(0.3f, a.value());
+  }
+
+  {
+    Optional<std::string> a("foo");
+    a.emplace("bar");
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ("bar", a.value());
+  }
+
+  {
+    Optional<TestObject> a(TestObject(0, 0.1));
+    a.emplace(TestObject(1, 0.2));
+
+    EXPECT_TRUE(a);
+    EXPECT_EQ(TestObject(1, 0.2), a.value());
+  }
+}
+
+// TODO: tests for the operator non-member functions. Some are already present.
+
+TEST(OptionalTest, MakeOptional) {
+  {
+    Optional<float> o = base::make_optional(32.f);
+    EXPECT_TRUE(o);
+    EXPECT_EQ(32.f, *o);
+
+    float value = 3.f;
+    o = base::make_optional(std::move(value));
+    EXPECT_TRUE(o);
+    EXPECT_EQ(3.f, *o);
+  }
+
+  {
+    Optional<const char*> o = base::make_optional("foo");
+    EXPECT_TRUE(o);
+    EXPECT_EQ("foo", *o);
+
+    const char* value = "bar";
+    o = base::make_optional(std::move(value));
+    EXPECT_TRUE(o);
+    EXPECT_EQ("bar", *o);
+  }
+
+  {
+    Optional<TestObject> o = base::make_optional(TestObject(3, 0.1));
+    EXPECT_TRUE(o);
+    EXPECT_EQ(TestObject(3, 0.1), *o);
+
+    TestObject value = TestObject(0, 0.42);
+    o = base::make_optional(std::move(value));
+    EXPECT_TRUE(o);
+    EXPECT_EQ(TestObject(0, 0.42), *o);
+    EXPECT_EQ(TestObject::State::MOVED_FROM, value.state());
+    EXPECT_EQ(TestObject::State::COPY_CONSTRUCTED, o->state());
+
+    EXPECT_EQ(TestObject::State::MOVE_CONSTRUCTED,
+              base::make_optional(std::move(value))->state());
+  }
+}
+
+TEST(OptionalTest, NonMemberSwap_bothNoValue) {
+  Optional<TestObject> a, b;
+  base::swap(a, b);
+
+  EXPECT_FALSE(a);
+  EXPECT_FALSE(b);
+  EXPECT_EQ(TestObject(42, 0.42), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(42, 0.42), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, NonMemberSwap_inHasValue) {
+  Optional<TestObject> a(TestObject(1, 0.3));
+  Optional<TestObject> b;
+  base::swap(a, b);
+
+  EXPECT_FALSE(a);
+  EXPECT_TRUE(b);
+  EXPECT_EQ(TestObject(42, 0.42), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(1, 0.3), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, NonMemberSwap_outHasValue) {
+  Optional<TestObject> a;
+  Optional<TestObject> b(TestObject(1, 0.3));
+  base::swap(a, b);
+
+  EXPECT_TRUE(a);
+  EXPECT_FALSE(b);
+  EXPECT_EQ(TestObject(1, 0.3), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(42, 0.42), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, NonMemberSwap_bothValue) {
+  Optional<TestObject> a(TestObject(0, 0.1));
+  Optional<TestObject> b(TestObject(1, 0.3));
+  base::swap(a, b);
+
+  EXPECT_TRUE(a);
+  EXPECT_TRUE(b);
+  EXPECT_EQ(TestObject(1, 0.3), a.value_or(TestObject(42, 0.42)));
+  EXPECT_EQ(TestObject(0, 0.1), b.value_or(TestObject(42, 0.42)));
+}
+
+TEST(OptionalTest, Hash) {
+  // TODO
+}
+
+}  // namespace base