exception_wrapper::from_exception_ptr

Summary:
[Folly] `exception_wrapper::from_exception_ptr`.

A handry helper for converting from `std::exception_ptr` to `folly::exception_wrapper`.

Reviewed By: ericniebler

Differential Revision: D5668179

fbshipit-source-id: a81a60cb22a2a697714268e027af62dd8825d2c3

folly/ExceptionWrapper.cpp

@@ -60,6 +60,20 @@ std::exception const* get_std_exception_(std::exception_ptr eptr) noexcept {
 }
 }
 
+exception_wrapper exception_wrapper::from_exception_ptr(
+    std::exception_ptr const& ptr) noexcept {
+  if (!ptr) {
+    return exception_wrapper();
+  }
+  try {
+    std::rethrow_exception(ptr);
+  } catch (std::exception& e) {
+    return exception_wrapper(std::current_exception(), e);
+  } catch (...) {
+    return exception_wrapper(std::current_exception());
+  }
+}
+
 exception_wrapper::exception_wrapper(std::exception_ptr ptr) noexcept
     : exception_wrapper{} {
   if (ptr) {

folly/ExceptionWrapper.h

@@ -368,6 +368,9 @@ class exception_wrapper final {
   static bool with_exception_(This& this_, Fn fn_);
 
  public:
+  static exception_wrapper from_exception_ptr(
+      std::exception_ptr const& eptr) noexcept;
+
   //! Default-constructs an empty `exception_wrapper`
   //! \post `type() == none()`
   exception_wrapper() noexcept {}

folly/test/ExceptionWrapperTest.cpp

@@ -209,6 +209,28 @@ TEST(ExceptionWrapper, get_or_make_exception_ptr_test) {
   EXPECT_FALSE(eptr);
 }
 
+TEST(ExceptionWrapper, from_exception_ptr_empty) {
+  auto ep = std::exception_ptr();
+  auto ew = exception_wrapper::from_exception_ptr(ep);
+  EXPECT_FALSE(bool(ew));
+}
+
+TEST(ExceptionWrapper, from_exception_ptr_exn) {
+  auto ep = std::make_exception_ptr(std::runtime_error("foo"));
+  auto ew = exception_wrapper::from_exception_ptr(ep);
+  EXPECT_TRUE(bool(ew));
+  EXPECT_EQ(ep, ew.to_exception_ptr());
+  EXPECT_TRUE(ew.is_compatible_with<std::runtime_error>());
+}
+
+TEST(ExceptionWrapper, from_exception_ptr_any) {
+  auto ep = std::make_exception_ptr<int>(12);
+  auto ew = exception_wrapper::from_exception_ptr(ep);
+  EXPECT_TRUE(bool(ew));
+  EXPECT_EQ(ep, ew.to_exception_ptr());
+  EXPECT_TRUE(ew.is_compatible_with<int>());
+}
+
 TEST(ExceptionWrapper, with_exception_ptr_empty) {
   auto ew = exception_wrapper(std::exception_ptr());
   EXPECT_EQ(exception_wrapper::none(), ew.type());