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/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) {