Move result.h from init to libbase
The Result, Error, ErrnoError are quite generic. Moving them from init
to libbase so that they can be used from other places.
Bug: 132145659
Test: libbase_test
Change-Id: Id774a587f74380fadd7a0fc88c0aa892c3d9a489
diff --git a/result_test.cpp b/result_test.cpp
new file mode 100644
index 0000000..6874889
--- /dev/null
+++ b/result_test.cpp
@@ -0,0 +1,357 @@
+/*
+ * 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 "android-base/result.h"
+
+#include "errno.h"
+
+#include <istream>
+#include <string>
+
+#include <gtest/gtest.h>
+
+using namespace std::string_literals;
+
+namespace android {
+namespace base {
+
+TEST(result, result_accessors) {
+ Result<std::string> result = "success";
+ ASSERT_TRUE(result);
+ ASSERT_TRUE(result.has_value());
+
+ EXPECT_EQ("success", *result);
+ EXPECT_EQ("success", result.value());
+
+ EXPECT_EQ('s', result->data()[0]);
+}
+
+TEST(result, result_accessors_rvalue) {
+ ASSERT_TRUE(Result<std::string>("success"));
+ ASSERT_TRUE(Result<std::string>("success").has_value());
+
+ EXPECT_EQ("success", *Result<std::string>("success"));
+ EXPECT_EQ("success", Result<std::string>("success").value());
+
+ EXPECT_EQ('s', Result<std::string>("success")->data()[0]);
+}
+
+TEST(result, result_success) {
+ Result<Success> result = Success();
+ ASSERT_TRUE(result);
+ ASSERT_TRUE(result.has_value());
+
+ EXPECT_EQ(Success(), *result);
+ EXPECT_EQ(Success(), result.value());
+}
+
+TEST(result, result_success_rvalue) {
+ // Success() doesn't actually create a Result<Success> object, but rather an object that can be
+ // implicitly constructed into a Result<Success> object.
+
+ auto MakeRvalueSuccessResult = []() -> Result<Success> { return Success(); };
+ ASSERT_TRUE(MakeRvalueSuccessResult());
+ ASSERT_TRUE(MakeRvalueSuccessResult().has_value());
+
+ EXPECT_EQ(Success(), *MakeRvalueSuccessResult());
+ EXPECT_EQ(Success(), MakeRvalueSuccessResult().value());
+}
+
+TEST(result, result_error) {
+ Result<Success> result = Error() << "failure" << 1;
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ EXPECT_EQ(0, result.error().code());
+ EXPECT_EQ("failure1", result.error().message());
+}
+
+TEST(result, result_error_empty) {
+ Result<Success> result = Error();
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ EXPECT_EQ(0, result.error().code());
+ EXPECT_EQ("", result.error().message());
+}
+
+TEST(result, result_error_rvalue) {
+ // Error() and ErrnoError() aren't actually used to create a Result<T> object.
+ // Under the hood, they are an intermediate class that can be implicitly constructed into a
+ // Result<T>. This is needed both to create the ostream and because Error() itself, by
+ // definition will not know what the type, T, of the underlying Result<T> object that it would
+ // create is.
+
+ auto MakeRvalueErrorResult = []() -> Result<Success> { return Error() << "failure" << 1; };
+ ASSERT_FALSE(MakeRvalueErrorResult());
+ ASSERT_FALSE(MakeRvalueErrorResult().has_value());
+
+ EXPECT_EQ(0, MakeRvalueErrorResult().error().code());
+ EXPECT_EQ("failure1", MakeRvalueErrorResult().error().message());
+}
+
+TEST(result, result_errno_error) {
+ constexpr int test_errno = 6;
+ errno = test_errno;
+ Result<Success> result = ErrnoError() << "failure" << 1;
+
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ EXPECT_EQ(test_errno, result.error().code());
+ EXPECT_EQ("failure1: "s + strerror(test_errno), result.error().message());
+}
+
+TEST(result, result_errno_error_no_text) {
+ constexpr int test_errno = 6;
+ errno = test_errno;
+ Result<Success> result = ErrnoError();
+
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ EXPECT_EQ(test_errno, result.error().code());
+ EXPECT_EQ(strerror(test_errno), result.error().message());
+}
+
+TEST(result, result_error_from_other_result) {
+ auto error_text = "test error"s;
+ Result<Success> result = Error() << error_text;
+
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ Result<std::string> result2 = result.error();
+
+ ASSERT_FALSE(result2);
+ ASSERT_FALSE(result2.has_value());
+
+ EXPECT_EQ(0, result.error().code());
+ EXPECT_EQ(error_text, result.error().message());
+}
+
+TEST(result, result_error_through_ostream) {
+ auto error_text = "test error"s;
+ Result<Success> result = Error() << error_text;
+
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ Result<std::string> result2 = Error() << result.error();
+
+ ASSERT_FALSE(result2);
+ ASSERT_FALSE(result2.has_value());
+
+ EXPECT_EQ(0, result.error().code());
+ EXPECT_EQ(error_text, result.error().message());
+}
+
+TEST(result, result_errno_error_through_ostream) {
+ auto error_text = "test error"s;
+ constexpr int test_errno = 6;
+ errno = 6;
+ Result<Success> result = ErrnoError() << error_text;
+
+ errno = 0;
+
+ ASSERT_FALSE(result);
+ ASSERT_FALSE(result.has_value());
+
+ Result<std::string> result2 = Error() << result.error();
+
+ ASSERT_FALSE(result2);
+ ASSERT_FALSE(result2.has_value());
+
+ EXPECT_EQ(test_errno, result.error().code());
+ EXPECT_EQ(error_text + ": " + strerror(test_errno), result.error().message());
+}
+
+TEST(result, constructor_forwarding) {
+ auto result = Result<std::string>(std::in_place, 5, 'a');
+
+ ASSERT_TRUE(result);
+ ASSERT_TRUE(result.has_value());
+
+ EXPECT_EQ("aaaaa", *result);
+}
+
+struct ConstructorTracker {
+ static size_t constructor_called;
+ static size_t copy_constructor_called;
+ static size_t move_constructor_called;
+ static size_t copy_assignment_called;
+ static size_t move_assignment_called;
+
+ template <typename T>
+ ConstructorTracker(T&& string) : string(string) {
+ ++constructor_called;
+ }
+
+ ConstructorTracker(const ConstructorTracker& ct) {
+ ++copy_constructor_called;
+ string = ct.string;
+ }
+ ConstructorTracker(ConstructorTracker&& ct) noexcept {
+ ++move_constructor_called;
+ string = std::move(ct.string);
+ }
+ ConstructorTracker& operator=(const ConstructorTracker& ct) {
+ ++copy_assignment_called;
+ string = ct.string;
+ return *this;
+ }
+ ConstructorTracker& operator=(ConstructorTracker&& ct) noexcept {
+ ++move_assignment_called;
+ string = std::move(ct.string);
+ return *this;
+ }
+
+ std::string string;
+};
+
+size_t ConstructorTracker::constructor_called = 0;
+size_t ConstructorTracker::copy_constructor_called = 0;
+size_t ConstructorTracker::move_constructor_called = 0;
+size_t ConstructorTracker::copy_assignment_called = 0;
+size_t ConstructorTracker::move_assignment_called = 0;
+
+Result<ConstructorTracker> ReturnConstructorTracker(const std::string& in) {
+ if (in.empty()) {
+ return "literal string";
+ }
+ if (in == "test2") {
+ return ConstructorTracker(in + in + "2");
+ }
+ ConstructorTracker result(in + " " + in);
+ return result;
+};
+
+TEST(result, no_copy_on_return) {
+ // If returning parameters that may be used to implicitly construct the type T of Result<T>,
+ // then those parameters are forwarded to the construction of Result<T>.
+
+ // If returning an prvalue or xvalue, it will be move constructed during the construction of
+ // Result<T>.
+
+ // This check ensures that that is the case, and particularly that no copy constructors
+ // are called.
+
+ auto result1 = ReturnConstructorTracker("");
+ ASSERT_TRUE(result1);
+ EXPECT_EQ("literal string", result1->string);
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ auto result2 = ReturnConstructorTracker("test2");
+ ASSERT_TRUE(result2);
+ EXPECT_EQ("test2test22", result2->string);
+ EXPECT_EQ(2U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ auto result3 = ReturnConstructorTracker("test3");
+ ASSERT_TRUE(result3);
+ EXPECT_EQ("test3 test3", result3->string);
+ EXPECT_EQ(3U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(2U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+}
+
+// Below two tests require that we do not hide the move constructor with our forwarding reference
+// constructor. This is done with by disabling the forwarding reference constructor if its first
+// and only type is Result<T>.
+TEST(result, result_result_with_success) {
+ auto return_result_result_with_success = []() -> Result<Result<Success>> {
+ return Result<Success>();
+ };
+ auto result = return_result_result_with_success();
+ ASSERT_TRUE(result);
+ ASSERT_TRUE(*result);
+
+ auto inner_result = result.value();
+ ASSERT_TRUE(inner_result);
+}
+
+TEST(result, result_result_with_failure) {
+ auto return_result_result_with_error = []() -> Result<Result<Success>> {
+ return Result<Success>(ResultError("failure string", 6));
+ };
+ auto result = return_result_result_with_error();
+ ASSERT_TRUE(result);
+ ASSERT_FALSE(*result);
+ EXPECT_EQ("failure string", (*result).error().message());
+ EXPECT_EQ(6, (*result).error().code());
+}
+
+// This test requires that we disable the forwarding reference constructor if Result<T> is the
+// *only* type that we are forwarding. In otherwords, if we are forwarding Result<T>, int to
+// construct a Result<T>, then we still need the constructor.
+TEST(result, result_two_parameter_constructor_same_type) {
+ struct TestStruct {
+ TestStruct(int value) : value_(value) {}
+ TestStruct(Result<TestStruct> result, int value) : value_(result->value_ * value) {}
+ int value_;
+ };
+
+ auto return_test_struct = []() -> Result<TestStruct> {
+ return Result<TestStruct>(std::in_place, Result<TestStruct>(std::in_place, 6), 6);
+ };
+
+ auto result = return_test_struct();
+ ASSERT_TRUE(result);
+ EXPECT_EQ(36, result->value_);
+}
+
+TEST(result, die_on_access_failed_result) {
+ Result<std::string> result = Error();
+ ASSERT_DEATH(*result, "");
+}
+
+TEST(result, die_on_get_error_succesful_result) {
+ Result<std::string> result = "success";
+ ASSERT_DEATH(result.error(), "");
+}
+
+template <class CharT>
+std::basic_ostream<CharT>& SetErrnoToTwo(std::basic_ostream<CharT>& ss) {
+ errno = 2;
+ return ss;
+}
+
+TEST(result, preserve_errno) {
+ errno = 1;
+ int old_errno = errno;
+ Result<int> result = Error() << "Failed" << SetErrnoToTwo<char>;
+ ASSERT_FALSE(result);
+ EXPECT_EQ(old_errno, errno);
+
+ errno = 1;
+ old_errno = errno;
+ Result<int> result2 = ErrnoError() << "Failed" << SetErrnoToTwo<char>;
+ ASSERT_FALSE(result2);
+ EXPECT_EQ(old_errno, errno);
+ EXPECT_EQ(old_errno, result2.error().code());
+}
+
+} // namespace base
+} // namespace android