specialize UniversalPrinter<> for std::optional

googletest/include/gtest/gtest-printers.h

@@ -113,7 +113,6 @@
 
 #if GTEST_HAS_ABSL
 #include "absl/strings/string_view.h"
-#include "absl/types/optional.h"
 #endif  // GTEST_HAS_ABSL
 
 namespace testing {
@@ -680,14 +679,14 @@ class UniversalPrinter {
   GTEST_DISABLE_MSC_WARNINGS_POP_()
 };
 
-#if GTEST_HAS_ABSL
+#if GTEST_INTERNAL_HAS_OPTIONAL
 
-// Printer for absl::optional
+// Printer for std::optional / absl::optional
 
 template <typename T>
-class UniversalPrinter<::absl::optional<T>> {
+class UniversalPrinter<Optional<T>> {
  public:
-  static void Print(const ::absl::optional<T>& value, ::std::ostream* os) {
+  static void Print(const Optional<T>& value, ::std::ostream* os) {
     *os << '(';
     if (!value) {
       *os << "nullopt";
@@ -698,7 +697,7 @@ class UniversalPrinter<::absl::optional<T>> {
   }
 };
 
-#endif  // GTEST_HAS_ABSL
+#endif  // GTEST_INTERNAL_HAS_OPTIONAL
 
 #if GTEST_INTERNAL_HAS_VARIANT
 

googletest/include/gtest/internal/gtest-port.h

@@ -199,6 +199,8 @@
 //                                        suppressed (constant conditional).
 //   GTEST_INTENTIONAL_CONST_COND_POP_  - finish code section where MSVC C4127
 //                                        is suppressed.
+//   GTEST_INTERNAL_HAS_OPTIONAL - for enabling UniversalPrinter<std::optional> or
+//                                 UniversalPrinter<absl::optional> specializations.
 //   GTEST_INTERNAL_HAS_STRING_VIEW - for enabling Matcher<std::string_view> or
 //                                    Matcher<absl::string_view>
 //                                    specializations.
@@ -2225,6 +2227,36 @@ const char* StringFromGTestEnv(const char* flag, const char* default_val);
 
 #endif  // !defined(GTEST_INTERNAL_DEPRECATED)
 
+#if GTEST_HAS_ABSL
+// Always use absl::optional for UniversalPrinter<> specializations if googletest
+// is built with absl support.
+# define GTEST_INTERNAL_HAS_OPTIONAL 1
+#include "absl/types/optional.h"
+namespace testing {
+namespace internal {
+template <typename T>
+using Optional = ::absl::optional<T>;
+}  // namespace internal
+}  // namespace testing
+#else
+# ifdef __has_include
+#   if __has_include(<optional>) && __cplusplus >= 201703L
+// Otherwise for C++17 and higher use std::optional for UniversalPrinter<>
+// specializations.
+#   define GTEST_INTERNAL_HAS_OPTIONAL 1
+#include <optional>
+namespace testing {
+namespace internal {
+template <typename T>
+using Optional = ::std::optional<T>;
+}  // namespace internal
+}  // namespace testing
+// The case where absl is configured NOT to alias std::optional is not
+// supported.
+#  endif  // __has_include(<optional>) && __cplusplus >= 201703L
+# endif  // __has_include
+#endif  // GTEST_HAS_ABSL
+
 #if GTEST_HAS_ABSL
 // Always use absl::string_view for Matcher<> specializations if googletest
 // is built with absl support.

googletest/test/googletest-printers-test.cc

@@ -1531,18 +1531,16 @@ TEST(UniversalTersePrintTupleFieldsToStringsTestWithStd, PrintsTersely) {
   EXPECT_EQ("\"a\"", result[1]);
 }
 
-#if GTEST_HAS_ABSL
-
+#if GTEST_INTERNAL_HAS_OPTIONAL
 TEST(PrintOptionalTest, Basic) {
-  absl::optional<int> value;
+  internal::Optional<int> value;
   EXPECT_EQ("(nullopt)", PrintToString(value));
   value = {7};
   EXPECT_EQ("(7)", PrintToString(value));
-  EXPECT_EQ("(1.1)", PrintToString(absl::optional<double>{1.1}));
-  EXPECT_EQ("(\"A\")", PrintToString(absl::optional<std::string>{"A"}));
+  EXPECT_EQ("(1.1)", PrintToString(internal::Optional<double>{1.1}));
+  EXPECT_EQ("(\"A\")", PrintToString(internal::Optional<std::string>{"A"}));
 }
-
-#endif  // GTEST_HAS_ABSL
+#endif  // GTEST_INTERNAL_HAS_OPTIONAL
 
 #if GTEST_INTERNAL_HAS_VARIANT
 struct NonPrintable {