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

12 files changed, 548 insertions, 453 deletions

diff --git a/base/Android.bp b/base/Android.bp
index 58d3a5043..25a9f6884 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -141,6 +141,7 @@ cc_test {
         "parsenetaddress_test.cpp",
         "properties_test.cpp",
         "quick_exit_test.cpp",
+        "result_test.cpp",
         "scopeguard_test.cpp",
         "stringprintf_test.cpp",
         "strings_test.cpp",
diff --git a/base/include/android-base/result.h b/base/include/android-base/result.h
new file mode 100644
index 000000000..3cb39e6e2
--- /dev/null
+++ b/base/include/android-base/result.h
@@ -0,0 +1,164 @@
+/*
+ * 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.
+ */
+
+// This file contains classes for returning a successful result along with an optional
+// arbitrarily typed return value or for returning a failure result along with an optional string
+// indicating why the function failed.
+
+// There are 3 classes that implement this functionality and one additional helper type.
+//
+// Result<T> either contains a member of type T that can be accessed using similar semantics as
+// std::optional<T> or it contains a ResultError describing an error, which can be accessed via
+// Result<T>::error().
+//
+// ResultError is a type that contains both a std::string describing the error and a copy of errno
+// from when the error occurred.  ResultError can be used in an ostream directly to print its
+// string value.
+//
+// Success is a typedef that aids in creating Result<T> that do not contain a return value.
+// Result<Success> is the correct return type for a function that either returns successfully or
+// returns an error value.  Returning Success() from a function that returns Result<Success> is the
+// correct way to indicate that a function without a return type has completed successfully.
+//
+// A successful Result<T> is constructed implicitly from any type that can be implicitly converted
+// to T or from the constructor arguments for T.  This allows you to return a type T directly from
+// a function that returns Result<T>.
+//
+// Error and ErrnoError are used to construct a Result<T> that has failed.  The Error class takes
+// an ostream as an input and are implicitly cast to a Result<T> containing that failure.
+// ErrnoError() is a helper function to create an Error class that appends ": " + strerror(errno)
+// to the end of the failure string to aid in interacting with C APIs.  Alternatively, an errno
+// value can be directly specified via the Error() constructor.
+//
+// ResultError can be used in the ostream when using Error to construct a Result<T>.  In this case,
+// the string that the ResultError takes is passed through the stream normally, but the errno is
+// passed to the Result<T>.  This can be used to pass errno from a failing C function up multiple
+// callers.
+//
+// ResultError can also directly construct a Result<T>.  This is particularly useful if you have a
+// function that return Result<T> but you have a Result<U> and want to return its error.  In this
+// case, you can return the .error() from the Result<U> to construct the Result<T>.
+
+// An example of how to use these is below:
+// Result<U> CalculateResult(const T& input) {
+//   U output;
+//   if (!SomeOtherCppFunction(input, &output)) {
+//     return Error() << "SomeOtherCppFunction(" << input << ") failed";
+//   }
+//   if (!c_api_function(output)) {
+//     return ErrnoError() << "c_api_function(" << output << ") failed";
+//   }
+//   return output;
+// }
+//
+// auto output = CalculateResult(input);
+// if (!output) return Error() << "CalculateResult failed: " << output.error();
+// UseOutput(*output);
+
+#pragma once
+
+#include <errno.h>
+
+#include <sstream>
+#include <string>
+
+#include "android-base/expected.h"
+
+namespace android {
+namespace base {
+
+struct ResultError {
+  template <typename T>
+  ResultError(T&& message, int code)
+      : message_(std::forward<T>(message)), code_(code) {}
+
+  template <typename T>
+  operator android::base::expected<T, ResultError>() {
+    return android::base::unexpected(ResultError(message_, code_));
+  }
+
+  std::string message() const { return message_; }
+  int code() const { return code_; }
+
+ private:
+  std::string message_;
+  int code_;
+};
+
+inline std::ostream& operator<<(std::ostream& os, const ResultError& t) {
+  os << t.message();
+  return os;
+}
+
+class Error {
+ public:
+  Error() : errno_(0), append_errno_(false) {}
+  Error(int errno_to_append) : errno_(errno_to_append), append_errno_(true) {}
+
+  template <typename T>
+  operator android::base::expected<T, ResultError>() {
+    return android::base::unexpected(ResultError(str(), errno_));
+  }
+
+  template <typename T>
+  Error& operator<<(T&& t) {
+    int saved = errno;
+    ss_ << t;
+    errno = saved;
+    return *this;
+  }
+
+  Error& operator<<(const ResultError& result_error) {
+    (*this) << result_error.message();
+    errno_ = result_error.code();
+    return *this;
+  }
+
+  const std::string str() const {
+    std::string str = ss_.str();
+    if (append_errno_) {
+      if (str.empty()) {
+        return strerror(errno_);
+      }
+      return std::move(str) + ": " + strerror(errno_);
+    }
+    return str;
+  }
+
+  Error(const Error&) = delete;
+  Error(Error&&) = delete;
+  Error& operator=(const Error&) = delete;
+  Error& operator=(Error&&) = delete;
+
+ private:
+  std::stringstream ss_;
+  int errno_;
+  bool append_errno_;
+};
+
+inline Error ErrnoError() {
+  return Error(errno);
+}
+
+template <typename T>
+using Result = android::base::expected<T, ResultError>;
+
+// Usage: `Result<Success>` as a result type that doesn't contain a value.
+// Use `return {}` or `return Success()` to return with success.
+using Success = std::monostate;
+
+}  // namespace base
+}  // namespace android
diff --git a/base/result_test.cpp b/base/result_test.cpp
new file mode 100644
index 000000000..687488991
--- /dev/null
+++ b/base/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
diff --git a/init/Android.bp b/init/Android.bp
index eaa7fd73c..fa0a35c48 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -190,7 +190,6 @@ cc_test {
         "persistent_properties_test.cpp",
         "property_service_test.cpp",
         "property_type_test.cpp",
-        "result_test.cpp",
         "rlimit_parser_test.cpp",
         "service_test.cpp",
         "subcontext_test.cpp",
diff --git a/init/action.cpp b/init/action.cpp
index a4f69367c..a40172e68 100644
--- a/init/action.cpp
+++ b/init/action.cpp
@@ -127,7 +127,7 @@ void Action::ExecuteCommand(const Command& command) const {
     // report such failures unless we're running at the DEBUG log level.
     bool report_failure = !result.has_value();
     if (report_failure && android::base::GetMinimumLogSeverity() > android::base::DEBUG &&
-        result.error().as_errno == ENOENT) {
+        result.error().code() == ENOENT) {
         report_failure = false;
     }
 
@@ -139,7 +139,7 @@ void Action::ExecuteCommand(const Command& command) const {
 
         LOG(INFO) << "Command '" << cmd_str << "' action=" << trigger_name << " (" << filename_
                   << ":" << command.line() << ") took " << duration.count() << "ms and "
-                  << (result ? "succeeded" : "failed: " + result.error().as_string);
+                  << (result ? "succeeded" : "failed: " + result.error().message());
     }
 }
 
diff --git a/init/result.h b/init/result.h
index baa680dfe..984b25792 100644
--- a/init/result.h
+++ b/init/result.h
@@ -29,8 +29,8 @@
 // string value.
 //
 // Success is a typedef that aids in creating Result<T> that do not contain a return value.
-// Result<Success> is the correct return type for a function that either returns successfully or
-// returns an error value.  Returning Success() from a function that returns Result<Success> is the
+// Result<Nothing> is the correct return type for a function that either returns successfully or
+// returns an error value.  Returning Nothing() from a function that returns Result<Nothing> is the
 // correct way to indicate that a function without a return type has completed successfully.
 //
 // A successful Result<T> is constructed implicitly from any type that can be implicitly converted
@@ -70,101 +70,10 @@
 
 #pragma once
 
-#include <errno.h>
-
-#include <sstream>
-#include <string>
-
-#include <android-base/expected.h>
-
-namespace android {
-namespace init {
-
-struct ResultError {
-    template <typename T>
-    ResultError(T&& error_string, int error_errno)
-        : as_string(std::forward<T>(error_string)), as_errno(error_errno) {}
-
-    template <typename T>
-    operator android::base::expected<T, ResultError>() {
-        return android::base::unexpected(ResultError(as_string, as_errno));
-    }
-
-    std::string as_string;
-    int as_errno;
-};
-
-inline std::ostream& operator<<(std::ostream& os, const ResultError& t) {
-    os << t.as_string;
-    return os;
-}
-
-inline std::ostream& operator<<(std::ostream& os, ResultError&& t) {
-    os << std::move(t.as_string);
-    return os;
-}
-
-class Error {
-  public:
-    Error() : errno_(0), append_errno_(false) {}
-    Error(int errno_to_append) : errno_(errno_to_append), append_errno_(true) {}
-
-    template <typename T>
-    operator android::base::expected<T, ResultError>() {
-        return android::base::unexpected(ResultError(str(), errno_));
-    }
-
-    template <typename T>
-    Error&& operator<<(T&& t) {
-        ss_ << std::forward<T>(t);
-        return std::move(*this);
-    }
-
-    Error&& operator<<(const ResultError& result_error) {
-        ss_ << result_error.as_string;
-        errno_ = result_error.as_errno;
-        return std::move(*this);
-    }
-
-    Error&& operator<<(ResultError&& result_error) {
-        ss_ << std::move(result_error.as_string);
-        errno_ = result_error.as_errno;
-        return std::move(*this);
-    }
-
-    const std::string str() const {
-        std::string str = ss_.str();
-        if (append_errno_) {
-            if (str.empty()) {
-                return strerror(errno_);
-            }
-            return str + ": " + strerror(errno_);
-        }
-        return str;
-    }
-
-    int get_errno() const { return errno_; }
-
-    Error(const Error&) = delete;
-    Error(Error&&) = delete;
-    Error& operator=(const Error&) = delete;
-    Error& operator=(Error&&) = delete;
-
-  private:
-    std::stringstream ss_;
-    int errno_;
-    bool append_errno_;
-};
-
-inline Error ErrnoError() {
-    return Error(errno);
-}
-
-template <typename T>
-using Result = android::base::expected<T, ResultError>;
-
-using Success = std::monostate;
-
-}  // namespace init
-}  // namespace android
+#include <android-base/result.h>
 
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::Result;
+using android::base::ResultError;
+using android::base::Success;
diff --git a/init/result_test.cpp b/init/result_test.cpp
deleted file mode 100644
index d3d04a015..000000000
--- a/init/result_test.cpp
+++ /dev/null
@@ -1,335 +0,0 @@
-/*
- * 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 "result.h"
-
-#include "errno.h"
-
-#include <string>
-
-#include <gtest/gtest.h>
-
-using namespace std::string_literals;
-
-namespace android {
-namespace init {
-
-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().as_errno);
-    EXPECT_EQ("failure1", result.error().as_string);
-}
-
-TEST(result, result_error_empty) {
-    Result<Success> result = Error();
-    ASSERT_FALSE(result);
-    ASSERT_FALSE(result.has_value());
-
-    EXPECT_EQ(0, result.error().as_errno);
-    EXPECT_EQ("", result.error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ("failure1", MakeRvalueErrorResult().error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ("failure1: "s + strerror(test_errno), result.error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ(strerror(test_errno), result.error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ(error_text, result.error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ(error_text, result.error().as_string);
-}
-
-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().as_errno);
-    EXPECT_EQ(error_text + ": " + strerror(test_errno), result.error().as_string);
-}
-
-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().as_string);
-    EXPECT_EQ(6, (*result).error().as_errno);
-}
-
-// 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(), "");
-}
-
-}  // namespace init
-}  // namespace android
diff --git a/init/rlimit_parser_test.cpp b/init/rlimit_parser_test.cpp
index e690bf6d6..6a16d3b57 100644
--- a/init/rlimit_parser_test.cpp
+++ b/init/rlimit_parser_test.cpp
@@ -43,8 +43,8 @@ void TestRlimitFailure(std::vector<std::string> input, const std::string& expect
     auto result = ParseRlimit(input);
 
     ASSERT_FALSE(result) << "input: " << input[1];
-    EXPECT_EQ(expected_result, result.error().as_string);
-    EXPECT_EQ(0, result.error().as_errno);
+    EXPECT_EQ(expected_result, result.error().message());
+    EXPECT_EQ(0, result.error().code());
 }
 
 TEST(rlimit, RlimitSuccess) {
diff --git a/init/service.cpp b/init/service.cpp
index 8fe5b309a..a54cb6bdf 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -1196,7 +1196,7 @@ void ServiceList::MarkServicesUpdate() {
             continue;
         }
         if (auto result = service->Start(); !result) {
-            LOG(ERROR) << result.error().as_string;
+            LOG(ERROR) << result.error().message();
         }
     }
     delayed_service_names_.clear();
diff --git a/init/subcontext.cpp b/init/subcontext.cpp
index f9eb83def..0ff479a22 100644
--- a/init/subcontext.cpp
+++ b/init/subcontext.cpp
@@ -142,8 +142,8 @@ void SubcontextProcess::RunCommand(const SubcontextCommand::ExecuteCommand& exec
         reply->set_success(true);
     } else {
         auto* failure = reply->mutable_failure();
-        failure->set_error_string(result.error().as_string);
-        failure->set_error_errno(result.error().as_errno);
+        failure->set_error_string(result.error().message());
+        failure->set_error_errno(result.error().code());
     }
 }
 
@@ -178,7 +178,7 @@ void SubcontextProcess::MainLoop() {
 
         auto init_message = ReadMessage(init_fd_);
         if (!init_message) {
-            if (init_message.error().as_errno == 0) {
+            if (init_message.error().code() == 0) {
                 // If the init file descriptor was closed, let's exit quietly. If
                 // this was accidental, init will restart us. If init died, this
                 // avoids calling abort(3) unnecessarily.
diff --git a/init/subcontext_test.cpp b/init/subcontext_test.cpp
index c0662a471..263568300 100644
--- a/init/subcontext_test.cpp
+++ b/init/subcontext_test.cpp
@@ -69,7 +69,7 @@ TEST(subcontext, CheckDifferentPid) {
         auto result = subcontext.Execute(std::vector<std::string>{"return_pids_as_error"});
         ASSERT_FALSE(result);
 
-        auto pids = Split(result.error().as_string, " ");
+        auto pids = Split(result.error().message(), " ");
         ASSERT_EQ(2U, pids.size());
         auto our_pid = std::to_string(getpid());
         EXPECT_NE(our_pid, pids[0]);
@@ -116,7 +116,7 @@ TEST(subcontext, MultipleCommands) {
 
         auto result = subcontext.Execute(std::vector<std::string>{"return_words_as_error"});
         ASSERT_FALSE(result);
-        EXPECT_EQ(Join(expected_words, " "), result.error().as_string);
+        EXPECT_EQ(Join(expected_words, " "), result.error().message());
         EXPECT_EQ(first_pid, subcontext.pid());
     });
 }
@@ -130,7 +130,7 @@ TEST(subcontext, RecoverAfterAbort) {
 
         auto result2 = subcontext.Execute(std::vector<std::string>{"generate_sane_error"});
         ASSERT_FALSE(result2);
-        EXPECT_EQ("Sane error!", result2.error().as_string);
+        EXPECT_EQ("Sane error!", result2.error().message());
         EXPECT_NE(subcontext.pid(), first_pid);
     });
 }
@@ -139,7 +139,7 @@ TEST(subcontext, ContextString) {
     RunTest([](auto& subcontext, auto& context_string) {
         auto result = subcontext.Execute(std::vector<std::string>{"return_context_as_error"});
         ASSERT_FALSE(result);
-        ASSERT_EQ(context_string, result.error().as_string);
+        ASSERT_EQ(context_string, result.error().message());
     });
 }
 
@@ -167,7 +167,7 @@ TEST(subcontext, ExpandArgsFailure) {
         };
         auto result = subcontext.ExpandArgs(args);
         ASSERT_FALSE(result);
-        EXPECT_EQ("Failed to expand '" + args[1] + "'", result.error().as_string);
+        EXPECT_EQ("Failed to expand '" + args[1] + "'", result.error().message());
     });
 }
 
diff --git a/init/util_test.cpp b/init/util_test.cpp
index 8bf672c0e..8947256cf 100644
--- a/init/util_test.cpp
+++ b/init/util_test.cpp
@@ -34,7 +34,7 @@ TEST(util, ReadFile_ENOENT) {
     auto file_contents = ReadFile("/proc/does-not-exist");
     EXPECT_EQ(ENOENT, errno);
     ASSERT_FALSE(file_contents);
-    EXPECT_EQ("open() failed: No such file or directory", file_contents.error().as_string);
+    EXPECT_EQ("open() failed: No such file or directory", file_contents.error().message());
 }
 
 TEST(util, ReadFileGroupWriteable) {
@@ -45,7 +45,7 @@ TEST(util, ReadFileGroupWriteable) {
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0620, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
     auto file_contents = ReadFile(tf.path);
     ASSERT_FALSE(file_contents) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file", file_contents.error().as_string);
+    EXPECT_EQ("Skipping insecure file", file_contents.error().message());
 }
 
 TEST(util, ReadFileWorldWiteable) {
@@ -56,7 +56,7 @@ TEST(util, ReadFileWorldWiteable) {
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0602, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
     auto file_contents = ReadFile(tf.path);
     ASSERT_FALSE(file_contents) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file", file_contents.error().as_string);
+    EXPECT_EQ("Skipping insecure file", file_contents.error().message());
 }
 
 TEST(util, ReadFileSymbolicLink) {
@@ -66,7 +66,7 @@ TEST(util, ReadFileSymbolicLink) {
     EXPECT_EQ(ELOOP, errno);
     ASSERT_FALSE(file_contents);
     EXPECT_EQ("open() failed: Too many symbolic links encountered",
-              file_contents.error().as_string);
+              file_contents.error().message());
 }
 
 TEST(util, ReadFileSuccess) {
@@ -131,7 +131,7 @@ TEST(util, DecodeUid) {
 
     decoded_uid = DecodeUid("toot");
     EXPECT_FALSE(decoded_uid);
-    EXPECT_EQ("getpwnam failed: No such file or directory", decoded_uid.error().as_string);
+    EXPECT_EQ("getpwnam failed: No such file or directory", decoded_uid.error().message());
 
     decoded_uid = DecodeUid("123");
     EXPECT_TRUE(decoded_uid);