Bring sapi::StatusOr<> up to date with internal Abseil changes

Note: This intentionally omits perfect-forwarding value assignments. This
avoids overly complex template expressions. The regular assignments are still
efficient.
PiperOrigin-RevId: 304159053
Change-Id: I3460f46ca5779a0619cf90ae22625de8fad7669c

sandboxed_api/util/statusor.h

@@ -19,6 +19,9 @@
 #ifndef THIRD_PARTY_SAPI_UTIL_STATUSOR_H_
 #define THIRD_PARTY_SAPI_UTIL_STATUSOR_H_
 
+#include <initializer_list>
+#include <utility>
+
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/attributes.h"
 #include "absl/base/log_severity.h"
@@ -29,20 +32,15 @@
 namespace sapi {
 
 template <typename T>
-class StatusOr {
+class ABSL_MUST_USE_RESULT StatusOr {
+  template <typename U>
+  friend class StatusOr;
+
  public:
+  using element_type = T;
+
   explicit StatusOr() : variant_(absl::UnknownError("")) {}
 
-  StatusOr(const absl::Status& status) : variant_(status) { EnsureNotOk(); }
-
-  StatusOr& operator=(const absl::Status& status) {
-    variant_ = status;
-    EnsureNotOk();
-  }
-
-  StatusOr(const T& value) : variant_{value} {}
-  StatusOr(T&& value) : variant_{std::move(value)} {}
-
   StatusOr(const StatusOr&) = default;
   StatusOr& operator=(const StatusOr&) = default;
 
@@ -50,27 +48,84 @@ class StatusOr {
   StatusOr& operator=(StatusOr&&) = default;
 
   template <typename U>
-  StatusOr(const StatusOr<U>& other) {
-    *this = other;
-  }
+  StatusOr(const StatusOr<U>& other) : StatusOr(other) {}
+
+  template <typename U>
+  StatusOr(StatusOr<U>&& other) : StatusOr(other) {}
 
   template <typename U>
   StatusOr& operator=(const StatusOr<U>& other) {
-    if (other.ok()) {
-      variant_ = other.ValueOrDie();
-    } else {
-      variant_ = other.status();
-    }
+    variant_ = other.ok() ? other.value() : other.status();
     return *this;
   }
 
+  template <typename U>
+  StatusOr& operator=(StatusOr<U>&& other) {
+    variant_ =
+        other.ok() ? std::move(other).value() : std::move(other).status();
+    return *this;
+  }
+
+  StatusOr(const T& value) : variant_(value) {}
+
+  StatusOr(const absl::Status& status) : variant_(status) { EnsureNotOk(); }
+
+  // Not implemented:
+  // template <typename U = T>
+  // StatusOr& operator=(U&& value);
+
+  StatusOr(T&& value) : variant_(std::move(value)) {}
+
+  StatusOr(absl::Status&& value) : variant_(std::move(value)) {}
+
+  StatusOr& operator=(absl::Status&& status) {
+    variant_ = std::move(status);
+    EnsureNotOk();
+  }
+
+  template <typename... Args>
+  explicit StatusOr(absl::in_place_t, Args&&... args)
+      : StatusOr(T(std::forward<Args>(args)...)) {}
+
+  template <typename U, typename... Args>
+  explicit StatusOr(absl::in_place_t, std::initializer_list<U> ilist,
+                    Args&&... args)
+      : StatusOr(ilist, U(std::forward<Args>(args)...)) {}
+
   explicit operator bool() const { return ok(); }
+
   ABSL_MUST_USE_RESULT bool ok() const {
     return absl::holds_alternative<T>(variant_);
   }
 
-  absl::Status status() const {
-    return ok() ? absl::OkStatus() : absl::get<absl::Status>(variant_);
+  const absl::Status& status() const& {
+    static const auto* ok_status = new absl::Status();
+    return ok() ? *ok_status : absl::get<absl::Status>(variant_);
+  }
+
+  absl::Status status() && {
+    return ok() ? absl::OkStatus()
+                : std::move(absl::get<absl::Status>(variant_));
+  }
+
+  const T& value() const& {
+    EnsureOk();
+    return absl::get<T>(variant_);
+  }
+
+  T& value() & {
+    EnsureOk();
+    return absl::get<T>(variant_);
+  }
+
+  const T&& value() const&& {
+    EnsureOk();
+    return std::move(absl::get<T>(variant_));
+  }
+
+  T&& value() && {
+    EnsureOk();
+    return std::move(absl::get<T>(variant_));
   }
 
   const T& ValueOrDie() const& {
@@ -88,6 +143,65 @@ class StatusOr {
     return std::move(absl::get<T>(variant_));
   }
 
+  const T& operator*() const& {
+    EnsureOk();
+    return absl::get<T>(variant_);
+  }
+
+  T& operator*() & {
+    EnsureOk();
+    return absl::get<T>(variant_);
+  }
+
+  const T&& operator*() const&& {
+    EnsureOk();
+    return std::move(absl::get<T>(variant_));
+  }
+
+  T&& operator*() && {
+    EnsureOk();
+    return std::move(absl::get<T>(variant_));
+  }
+
+  const T* operator->() const {
+    EnsureOk();
+    return &absl::get<T>(variant_);
+  }
+
+  T* operator->() {
+    EnsureOk();
+    return &absl::get<T>(variant_);
+  }
+
+  template <typename U>
+  T value_or(U&& default_value) const& {
+    if (ok()) {
+      return absl::get<T>(variant_);
+    }
+    return std::forward<U>(default_value);
+  }
+
+  template <typename U>
+  T value_or(U&& default_value) && {
+    if (ok()) {
+      return std::move(absl::get<T>(variant_));
+    }
+    return std::forward<U>(default_value);
+  }
+
+  void IgnoreError() const { /* no-op */
+  }
+
+  template <typename... Args>
+  T& emplace(Args&&... args) {
+    return variant_.template emplace<T>(std::forward<Args>(args)...);
+  }
+
+  template <typename U, typename... Args>
+  T& emplace(std::initializer_list<U> ilist, Args&&... args) {
+    return variant_.template emplace<T>(ilist, std::forward<Args>(args)...);
+  }
+
  private:
   void EnsureOk() const {
     if (!ok()) {

sandboxed_api/util/statusor_test.cc

@@ -28,6 +28,7 @@
 using ::testing::Eq;
 using ::testing::IsFalse;
 using ::testing::Not;
+using ::testing::Pointee;
 
 namespace sapi {
 namespace {
@@ -366,5 +367,41 @@ TEST(StatusOrTest, ValueOrDieMovedValue) {
   EXPECT_THAT(*moved_value, Eq(kStringElement));
 }
 
+TEST(StatusOrTest, MapToStatusOrUniquePtr) {
+  // A reduced version of a problematic type found in the wild. All of the
+  // operations below should compile.
+  using MapType = std::map<std::string, StatusOr<std::unique_ptr<int>>>;
+
+  MapType a;
+
+  // Move-construction
+  MapType b(std::move(a));
+
+  // Move-assignment
+  a = std::move(b);
+}
+
+TEST(StatusOrTest, ValueOrOk) {
+  const StatusOr<int> status_or = 0;
+  EXPECT_EQ(status_or.value_or(-1), 0);
+}
+
+TEST(StatusOrTest, ValueOrDefault) {
+  const StatusOr<int> status_or = absl::CancelledError();
+  EXPECT_EQ(status_or.value_or(-1), -1);
+}
+
+TEST(StatusOrTest, MoveOnlyValueOrOk) {
+  EXPECT_THAT(StatusOr<std::unique_ptr<int>>(absl::make_unique<int>(0))
+                  .value_or(absl::make_unique<int>(-1)),
+              Pointee(0));
+}
+
+TEST(StatusOr, MoveOnlyValueOrDefault) {
+  EXPECT_THAT(StatusOr<std::unique_ptr<int>>(absl::CancelledError())
+                  .value_or(absl::make_unique<int>(-1)),
+              Pointee(-1));
+}
+
 }  // namespace
 }  // namespace sapi