Template get_optional on Optional type

Summary: Allows use with std::optional when available

Reviewed By: WillerZ

Differential Revision: D25618828

fbshipit-source-id: 3e039406ff1e885fd1767148b907635b23f7a88b

folly/MapUtil.h

@@ -98,15 +98,18 @@ typename Map::mapped_type& get_or_throw(
  * Given a map and a key, return a Optional<V> if the key exists and None if the
  * key does not exist in the map.
  */
-template <class Map, typename Key = typename Map::key_type>
-folly::Optional<typename Map::mapped_type> get_optional(
+template <
+    template <typename> class Optional = folly::Optional,
+    class Map,
+    typename Key = typename Map::key_type>
+Optional<typename Map::mapped_type> get_optional(
     const Map& map,
     const Key& key) {
   auto pos = map.find(key);
   if (pos != map.end()) {
-    return folly::Optional<typename Map::mapped_type>(pos->second);
+    return Optional<typename Map::mapped_type>(pos->second);
   } else {
-    return folly::none;
+    return {};
   }
 }
 

folly/test/MapUtilTest.cpp

@@ -98,6 +98,14 @@ TEST(MapUtil, get_optional_path_mixed) {
   EXPECT_TRUE(get_optional(m, "a"));
 }
 
+TEST(MapUtil, get_optional_std) {
+  std::map<int, int> m;
+  m[1] = 2;
+  EXPECT_TRUE(get_optional<std::optional>(m, 1).has_value());
+  EXPECT_EQ(2, get_optional<std::optional>(m, 1).value());
+  EXPECT_FALSE(get_optional<std::optional>(m, 2).has_value());
+}
+
 TEST(MapUtil, get_ref_default) {
   std::map<int, int> m;
   m[1] = 2;