Use the Abseil flags library when Abseil is present

When built with `--define=absl=1` under Bazel, GoogleTest
flags use ABSL_FLAG instead of GoogleTest's own implementation.

There are some minor behavior differences in this mode.

The most notable difference is that unrecognized flags result
in a flag parsing error, and are not returned to the user though
a modified argc/argv, unless they appear after the positional
argument delimiter ("--").

For example, to pass a non-Abseil flag, you would have to do
./mytest --gtest_color=false -- --myflag=myvalue

The documentation at https://abseil.io/docs/cpp/guides/flags
may be helpful in understanding the behavior.

There are some other minor differences. For example,
passing --help results in the program returning 1 instead of 0.

https://github.com/google/googletest/issues/3646

PiperOrigin-RevId: 439312700
Change-Id: Id696a25f50f24a5b1785c45ca8fa59794f86fd5c

1 files changed, 47 insertions, 20 deletions

diff --git a/googlemock/include/gmock/internal/gmock-port.h b/googlemock/include/gmock/internal/gmock-port.h
index f3e63c1..bc18a25 100644
--- a/googlemock/include/gmock/internal/gmock-port.h
+++ b/googlemock/include/gmock/internal/gmock-port.h
@@ -42,7 +42,6 @@
 
 #include <assert.h>
 #include <stdlib.h>
-
 #include <cstdint>
 #include <iostream>
 
@@ -57,6 +56,11 @@
 #include "gmock/internal/custom/gmock-port.h"
 #include "gtest/internal/gtest-port.h"
 
+#if GTEST_HAS_ABSL
+#include "absl/flags/declare.h"
+#include "absl/flags/flag.h"
+#endif
+
 // For MS Visual C++, check the compiler version. At least VS 2015 is
 // required to compile Google Mock.
 #if defined(_MSC_VER) && _MSC_VER < 1900
@@ -65,26 +69,33 @@
 
 // Macro for referencing flags.  This is public as we want the user to
 // use this syntax to reference Google Mock flags.
+#define GMOCK_FLAG_NAME_(name) gmock_##name
 #define GMOCK_FLAG(name) FLAGS_gmock_##name
 
-#if !defined(GMOCK_DECLARE_bool_)
+// Pick a command line flags implementation.
+#if GTEST_HAS_ABSL
+
+// Macros for defining flags.
+#define GMOCK_DEFINE_bool_(name, default_val, doc) \
+  ABSL_FLAG(bool, GMOCK_FLAG_NAME_(name), default_val, doc)
+#define GMOCK_DEFINE_int32_(name, default_val, doc) \
+  ABSL_FLAG(int32_t, GMOCK_FLAG_NAME_(name), default_val, doc)
+#define GMOCK_DEFINE_string_(name, default_val, doc) \
+  ABSL_FLAG(std::string, GMOCK_FLAG_NAME_(name), default_val, doc)
 
 // Macros for declaring flags.
-#define GMOCK_DECLARE_bool_(name)          \
-  namespace testing {                      \
-  GTEST_API_ extern bool GMOCK_FLAG(name); \
-  }                                        \
-  static_assert(true, "no-op to require trailing semicolon")
-#define GMOCK_DECLARE_int32_(name)            \
-  namespace testing {                         \
-  GTEST_API_ extern int32_t GMOCK_FLAG(name); \
-  }                                           \
-  static_assert(true, "no-op to require trailing semicolon")
-#define GMOCK_DECLARE_string_(name)                 \
-  namespace testing {                               \
-  GTEST_API_ extern ::std::string GMOCK_FLAG(name); \
-  }                                                 \
-  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DECLARE_bool_(name) \
+  ABSL_DECLARE_FLAG(bool, GMOCK_FLAG_NAME_(name))
+#define GMOCK_DECLARE_int32_(name) \
+  ABSL_DECLARE_FLAG(int32_t, GMOCK_FLAG_NAME_(name))
+#define GMOCK_DECLARE_string_(name) \
+  ABSL_DECLARE_FLAG(std::string, GMOCK_FLAG_NAME_(name))
+
+#define GMOCK_FLAG_GET(name) ::absl::GetFlag(GMOCK_FLAG(name))
+#define GMOCK_FLAG_SET(name, value) \
+  (void)(::absl::SetFlag(&GMOCK_FLAG(name), value))
+
+#else  // GTEST_HAS_ABSL
 
 // Macros for defining flags.
 #define GMOCK_DEFINE_bool_(name, default_val, doc)  \
@@ -102,11 +113,27 @@
   GTEST_API_ ::std::string GMOCK_FLAG(name) = (default_val); \
   }                                                          \
   static_assert(true, "no-op to require trailing semicolon")
-#endif  // !defined(GMOCK_DECLARE_bool_)
 
-#if !defined(GMOCK_FLAG_GET)
+// Macros for declaring flags.
+#define GMOCK_DECLARE_bool_(name)          \
+  namespace testing {                      \
+  GTEST_API_ extern bool GMOCK_FLAG(name); \
+  }                                        \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DECLARE_int32_(name)            \
+  namespace testing {                         \
+  GTEST_API_ extern int32_t GMOCK_FLAG(name); \
+  }                                           \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DECLARE_string_(name)                 \
+  namespace testing {                               \
+  GTEST_API_ extern ::std::string GMOCK_FLAG(name); \
+  }                                                 \
+  static_assert(true, "no-op to require trailing semicolon")
+
 #define GMOCK_FLAG_GET(name) ::testing::GMOCK_FLAG(name)
 #define GMOCK_FLAG_SET(name, value) (void)(::testing::GMOCK_FLAG(name) = value)
-#endif  // !defined(GMOCK_FLAG_GET)
+
+#endif  // GTEST_HAS_ABSL
 
 #endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_