feat(3p/absl): import StatusOr from tensorflow r/1391

Additionally, add tests for the macros. A future CL will enable the tests in CI.

Change-Id: Id4445a1aa65bf6751b87606f37654f3fc6d20efc
Tested-By: kanepyork <rikingcoding@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1274
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

1 files changed, 394 insertions, 0 deletions

diff --git a/third_party/abseil_cpp/absl/status/statusor.h b/third_party/abseil_cpp/absl/status/statusor.h
new file mode 100644
index 000000000000..59a52cb782b4
--- /dev/null
+++ b/third_party/abseil_cpp/absl/status/statusor.h
@@ -0,0 +1,394 @@
+/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
+
+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.
+==============================================================================*/
+
+// StatusOr<T> is the union of a Status object and a T object. StatusOr models
+// the concept of an object that is either a value, or an error Status
+// explaining why such a value is not present. To this end, StatusOr<T> does not
+// allow its Status value to be StatusCode::kOk.
+//
+// The primary use-case for StatusOr<T> is as the return value of a
+// function which may fail.
+//
+// Example client usage for a StatusOr<T>, where T is not a pointer:
+//
+//  StatusOr<float> result = DoBigCalculationThatCouldFail();
+//  if (result.ok()) {
+//    float answer = result.ValueOrDie();
+//    printf("Big calculation yielded: %f", answer);
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example client usage for a StatusOr<T*>:
+//
+//  StatusOr<Foo*> result = FooFactory::MakeNewFoo(arg);
+//  if (result.ok()) {
+//    std::unique_ptr<Foo> foo(result.ValueOrDie());
+//    foo->DoSomethingCool();
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example client usage for a StatusOr<std::unique_ptr<T>>:
+//
+//  StatusOr<std::unique_ptr<Foo>> result = FooFactory::MakeNewFoo(arg);
+//  if (result.ok()) {
+//    std::unique_ptr<Foo> foo = std::move(result.ValueOrDie());
+//    foo->DoSomethingCool();
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example factory implementation returning StatusOr<T*>:
+//
+//  StatusOr<Foo*> FooFactory::MakeNewFoo(int arg) {
+//    if (arg <= 0) {
+//      return absl::InvalidArgumentError("Arg must be positive");
+//    } else {
+//      return new Foo(arg);
+//    }
+//  }
+//
+// Note that the assignment operators require that destroying the currently
+// stored value cannot invalidate the argument; in other words, the argument
+// cannot be an alias for the current value, or anything owned by the current
+// value.
+#ifndef ABSL_STATUS_STATUSOR_H_
+#define ABSL_STATUS_STATUSOR_H_
+
+#include "absl/status/status.h"
+#include "absl/status/statusor_internals.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+template <typename T>
+class StatusOr : private internal_statusor::StatusOrData<T>,
+                 private internal_statusor::TraitsBase<
+                     std::is_copy_constructible<T>::value,
+                     std::is_move_constructible<T>::value> {
+  template <typename U>
+  friend class StatusOr;
+
+  typedef internal_statusor::StatusOrData<T> Base;
+
+ public:
+  typedef T element_type;  // DEPRECATED: use `value_type`.
+  typedef T value_type;
+
+  // Constructs a new StatusOr with Status::UNKNOWN status.  This is marked
+  // 'explicit' to try to catch cases like 'return {};', where people think
+  // StatusOr<std::vector<int>> will be initialized with an empty vector,
+  // instead of a Status::UNKNOWN status.
+  explicit StatusOr();
+
+  // StatusOr<T> will be copy constructible/assignable if T is copy
+  // constructible.
+  StatusOr(const StatusOr&) = default;
+  StatusOr& operator=(const StatusOr&) = default;
+
+  // StatusOr<T> will be move constructible/assignable if T is move
+  // constructible.
+  StatusOr(StatusOr&&) = default;
+  StatusOr& operator=(StatusOr&&) = default;
+
+  // Conversion copy/move constructor, T must be convertible from U.
+  template <typename U, typename std::enable_if<
+                            std::is_convertible<U, T>::value>::type* = nullptr>
+  StatusOr(const StatusOr<U>& other);
+  template <typename U, typename std::enable_if<
+                            std::is_convertible<U, T>::value>::type* = nullptr>
+  StatusOr(StatusOr<U>&& other);
+
+  // Conversion copy/move assignment operator, T must be convertible from U.
+  template <typename U, typename std::enable_if<
+                            std::is_convertible<U, T>::value>::type* = nullptr>
+  StatusOr& operator=(const StatusOr<U>& other);
+  template <typename U, typename std::enable_if<
+                            std::is_convertible<U, T>::value>::type* = nullptr>
+  StatusOr& operator=(StatusOr<U>&& other);
+
+  // Constructs a new StatusOr with the given value. After calling this
+  // constructor, calls to ValueOrDie() will succeed, and calls to status() will
+  // return OK.
+  //
+  // NOTE: Not explicit - we want to use StatusOr<T> as a return type
+  // so it is convenient and sensible to be able to do 'return T()'
+  // when the return type is StatusOr<T>.
+  //
+  // REQUIRES: T is copy constructible.
+  StatusOr(const T& value);
+
+  // Constructs a new StatusOr with the given non-ok status. After calling
+  // this constructor, calls to ValueOrDie() will CHECK-fail.
+  //
+  // NOTE: Not explicit - we want to use StatusOr<T> as a return
+  // value, so it is convenient and sensible to be able to do 'return
+  // Status()' when the return type is StatusOr<T>.
+  //
+  // REQUIRES: !status.ok(). This requirement is enforced with either an
+  // exception (the passed absl::Status) or a FATAL log.
+  StatusOr(const Status& status);
+  StatusOr& operator=(const Status& status);
+
+  // TODO(b/62186997): Add operator=(T) overloads.
+
+  // Similar to the `const T&` overload.
+  //
+  // REQUIRES: T is move constructible.
+  StatusOr(T&& value);
+
+  // RValue versions of the operations declared above.
+  StatusOr(Status&& status);
+  StatusOr& operator=(Status&& status);
+
+  // Returns this->status().ok()
+  bool ok() const { return this->status_.ok(); }
+
+  // Returns a reference to our status. If this contains a T, then
+  // returns OkStatus().
+  const Status& status() const &;
+  Status status() &&;
+
+  // Returns a reference to our current value, or CHECK-fails if !this->ok().
+  //
+  // Note: for value types that are cheap to copy, prefer simple code:
+  //
+  //   T value = statusor.ValueOrDie();
+  //
+  // Otherwise, if the value type is expensive to copy, but can be left
+  // in the StatusOr, simply assign to a reference:
+  //
+  //   T& value = statusor.ValueOrDie();  // or `const T&`
+  //
+  // Otherwise, if the value type supports an efficient move, it can be
+  // used as follows:
+  //
+  //   T value = std::move(statusor).ValueOrDie();
+  //
+  // The std::move on statusor instead of on the whole expression enables
+  // warnings about possible uses of the statusor object after the move.
+  // C++ style guide waiver for ref-qualified overloads granted in cl/143176389
+  // See go/ref-qualifiers for more details on such overloads.
+  const T& ValueOrDie() const &;
+  T& ValueOrDie() &;
+  const T&& ValueOrDie() const &&;
+  T&& ValueOrDie() &&;
+
+  // Returns a reference to the current value.
+  //
+  // REQUIRES: this->ok() == true, otherwise the behavior is undefined.
+  //
+  // Use this->ok() or `operator bool()` to verify that there is a current
+  // value. Alternatively, see ValueOrDie() for a similar API that guarantees
+  // CHECK-failing if there is no current value.
+  const T& operator*() const&;
+  T& operator*() &;
+  const T&& operator*() const&&;
+  T&& operator*() &&;
+
+  // Returns a pointer to the current value.
+  //
+  // REQUIRES: this->ok() == true, otherwise the behavior is undefined.
+  //
+  // Use this->ok() or `operator bool()` to verify that there is a current
+  // value.
+  const T* operator->() const;
+  T* operator->();
+
+  T ConsumeValueOrDie() { return std::move(ValueOrDie()); }
+
+  // Ignores any errors. This method does nothing except potentially suppress
+  // complaints from any tools that are checking that errors are not dropped on
+  // the floor.
+  void IgnoreError() const;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+// Implementation details for StatusOr<T>
+
+template <typename T>
+StatusOr<T>::StatusOr() : Base(Status(StatusCode::kUnknown, "")) {}
+
+template <typename T>
+StatusOr<T>::StatusOr(const T& value) : Base(value) {}
+
+template <typename T>
+StatusOr<T>::StatusOr(const Status& status) : Base(status) {}
+
+template <typename T>
+StatusOr<T>& StatusOr<T>::operator=(const Status& status) {
+  this->Assign(status);
+  return *this;
+}
+
+template <typename T>
+StatusOr<T>::StatusOr(T&& value) : Base(std::move(value)) {}
+
+template <typename T>
+StatusOr<T>::StatusOr(Status&& status) : Base(std::move(status)) {}
+
+template <typename T>
+StatusOr<T>& StatusOr<T>::operator=(Status&& status) {
+  this->Assign(std::move(status));
+  return *this;
+}
+
+template <typename T>
+template <typename U,
+          typename std::enable_if<std::is_convertible<U, T>::value>::type*>
+inline StatusOr<T>::StatusOr(const StatusOr<U>& other)
+    : Base(static_cast<const typename StatusOr<U>::Base&>(other)) {}
+
+template <typename T>
+template <typename U,
+          typename std::enable_if<std::is_convertible<U, T>::value>::type*>
+inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<U>& other) {
+  if (other.ok())
+    this->Assign(other.ValueOrDie());
+  else
+    this->Assign(other.status());
+  return *this;
+}
+
+template <typename T>
+template <typename U,
+          typename std::enable_if<std::is_convertible<U, T>::value>::type*>
+inline StatusOr<T>::StatusOr(StatusOr<U>&& other)
+    : Base(static_cast<typename StatusOr<U>::Base&&>(other)) {}
+
+template <typename T>
+template <typename U,
+          typename std::enable_if<std::is_convertible<U, T>::value>::type*>
+inline StatusOr<T>& StatusOr<T>::operator=(StatusOr<U>&& other) {
+  if (other.ok()) {
+    this->Assign(std::move(other).ValueOrDie());
+  } else {
+    this->Assign(std::move(other).status());
+  }
+  return *this;
+}
+
+template <typename T>
+const Status& StatusOr<T>::status() const & {
+  return this->status_;
+}
+template <typename T>
+Status StatusOr<T>::status() && {
+  // Note that we copy instead of moving the status here so that
+  // ~StatusOrData() can call ok() without invoking UB.
+  return ok() ? OkStatus() : this->status_;
+}
+
+template <typename T>
+const T& StatusOr<T>::ValueOrDie() const & {
+  this->EnsureOk();
+  return this->data_;
+}
+
+template <typename T>
+T& StatusOr<T>::ValueOrDie() & {
+  this->EnsureOk();
+  return this->data_;
+}
+
+template <typename T>
+const T&& StatusOr<T>::ValueOrDie() const && {
+  this->EnsureOk();
+  return std::move(this->data_);
+}
+
+template <typename T>
+T&& StatusOr<T>::ValueOrDie() && {
+  this->EnsureOk();
+  return std::move(this->data_);
+}
+
+template <typename T>
+const T* StatusOr<T>::operator->() const {
+  this->EnsureOk();
+  return &this->data_;
+}
+
+template <typename T>
+T* StatusOr<T>::operator->() {
+  this->EnsureOk();
+  return &this->data_;
+}
+
+template <typename T>
+const T& StatusOr<T>::operator*() const& {
+  this->EnsureOk();
+  return this->data_;
+}
+
+template <typename T>
+T& StatusOr<T>::operator*() & {
+  this->EnsureOk();
+  return this->data_;
+}
+
+template <typename T>
+const T&& StatusOr<T>::operator*() const&& {
+  this->EnsureOk();
+  return std::move(this->data_);
+}
+
+template <typename T>
+T&& StatusOr<T>::operator*() && {
+  this->EnsureOk();
+  return std::move(this->data_);
+}
+
+template <typename T>
+void StatusOr<T>::IgnoreError() const {
+  // no-op
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#define ASSERT_OK_AND_ASSIGN(lhs, rexpr)                                  \
+  ABSL_ASSERT_OK_AND_ASSIGN_IMPL(                                         \
+      ABSL_STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, \
+      rexpr);
+
+#define ABSL_ASSERT_OK_AND_ASSIGN_IMPL(statusor, lhs, rexpr)  \
+  auto statusor = (rexpr);                                    \
+  ASSERT_TRUE(statusor.status().ok()) << statusor.status();   \
+  lhs = std::move(statusor.ValueOrDie())
+
+#define ABSL_STATUS_MACROS_CONCAT_NAME(x, y) ABSL_STATUS_MACROS_CONCAT_IMPL(x, y)
+#define ABSL_STATUS_MACROS_CONCAT_IMPL(x, y) x##y
+
+#define ASSIGN_OR_RETURN(lhs, rexpr) \
+  ABSL_ASSIGN_OR_RETURN_IMPL(        \
+      ABSL_STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr)
+
+#define ABSL_ASSIGN_OR_RETURN_IMPL(statusor, lhs, rexpr) \
+  auto statusor = (rexpr);                               \
+  if (ABSL_PREDICT_FALSE(!statusor.ok())) {              \
+    return statusor.status();                            \
+  }                                                      \
+  lhs = std::move(statusor.ValueOrDie())
+
+#define RETURN_IF_ERROR(status)             \
+  do {                                      \
+    if (ABSL_PREDICT_FALSE(!status.ok())) { \
+      return status;                        \
+    }                                       \
+  } while(0)
+
+#endif  // ABSL_STATUS_STATUSOR_H_