Make testing::Message support streamed AbslStringify values

This allows types that provide an AbslStringify definition to be streamed into GoogleTest macros.

PiperOrigin-RevId: 552914482
Change-Id: I5fb386980d4d24873f95f0a8ef83067a6a3c86ac

googletest/include/gtest/gtest-message.h

@@ -56,6 +56,13 @@
 
 #include "gtest/internal/gtest-port.h"
 
+#ifdef GTEST_HAS_ABSL
+#include <type_traits>
+
+#include "absl/strings/internal/has_absl_stringify.h"
+#include "absl/strings/str_cat.h"
+#endif  // GTEST_HAS_ABSL
+
 GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
 /* class A needs to have dll-interface to be used by clients of class B */)
 
@@ -111,8 +118,17 @@ class GTEST_API_ Message {
     *ss_ << str;
   }
 
-  // Streams a non-pointer value to this object.
-  template <typename T>
+  // Streams a non-pointer value to this object. If building a version of
+  // GoogleTest with ABSL, this overload is only enabled if the value does not
+  // have an AbslStringify definition.
+  template <typename T
+#ifdef GTEST_HAS_ABSL
+            ,
+            typename std::enable_if<
+                !absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
+                int>::type = 0
+#endif  // GTEST_HAS_ABSL
+            >
   inline Message& operator<<(const T& val) {
         // Some libraries overload << for STL containers.  These
     // overloads are defined in the global namespace instead of ::std.
@@ -133,6 +149,22 @@ class GTEST_API_ Message {
     return *this;
   }
 
+#ifdef GTEST_HAS_ABSL
+  // Streams a non-pointer value with an AbslStringify definition to this
+  // object.
+  template <typename T,
+            typename std::enable_if<
+                absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
+                int>::type = 0>
+  inline Message& operator<<(const T& val) {
+    // ::operator<< is needed here for a similar reason as with the non-Abseil
+    // version above
+    using ::operator<<;
+    *ss_ << absl::StrCat(val);
+    return *this;
+  }
+#endif  // GTEST_HAS_ABSL
+
   // Streams a pointer value to this object.
   //
   // This function is an overload of the previous one.  When you

googletest/test/googletest-message-test.cc

@@ -36,10 +36,26 @@
 #include "gtest/gtest-message.h"
 #include "gtest/gtest.h"
 
+#ifdef GTEST_HAS_ABSL
+#include "absl/strings/str_format.h"
+#endif  // GTEST_HAS_ABSL
+
 namespace {
 
 using ::testing::Message;
 
+#ifdef GTEST_HAS_ABSL
+struct AbslStringifiablePoint {
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const AbslStringifiablePoint& p) {
+    absl::Format(&sink, "(%d, %d)", p.x, p.y);
+  }
+
+  int x;
+  int y;
+};
+#endif  // GTEST_HAS_ABSL
+
 // Tests the testing::Message class
 
 // Tests the default constructor.
@@ -128,6 +144,13 @@ TEST(MessageTest, StreamsInt) {
   EXPECT_EQ("123", (Message() << 123).GetString());
 }
 
+#ifdef GTEST_HAS_ABSL
+// Tests streaming a type with an AbslStringify definition.
+TEST(MessageTest, StreamsAbslStringify) {
+  EXPECT_EQ("(1, 2)", (Message() << AbslStringifiablePoint{1, 2}).GetString());
+}
+#endif  // GTEST_HAS_ABSL
+
 // Tests that basic IO manipulators (endl, ends, and flush) can be
 // streamed to Message.
 TEST(MessageTest, StreamsBasicIoManip) {