Fix logging when absl::SourceLocation is an alias of std::source_location

Prior to this change logging absl::SourceLocation sometimes worked
when //absl/strings/internal/stringify_sink.h was in the transitive
includes, usually through str_cat.h.

This change adds native support to logging, to avoid dependency issues.

PiperOrigin-RevId: 922782911
Change-Id: I599390a062c6f8828985d6475a6dbd324d3e52c9

absl/log/BUILD.bazel

@@ -502,6 +502,7 @@ cc_test(
         "//absl/log/internal:test_matchers",
         "//absl/strings",
         "//absl/strings:str_format",
+        "//absl/types:source_location",
         "@googletest//:gtest",
         "@googletest//:gtest_main",
     ],

absl/log/CMakeLists.txt

@@ -1017,6 +1017,7 @@ absl_cc_test(
     absl::log
     absl::log_internal_test_matchers
     absl::scoped_mock_log
+    absl::source_location
     absl::str_format
     absl::strings
     GTest::gmock_main

absl/log/internal/log_message.h

@@ -179,6 +179,13 @@ class LogMessage {
   LogMessage& operator<<(wchar_t* absl_nullable v);
   LogMessage& operator<<(wchar_t v);
 
+  // Overload for absl::SourceLocation or the std::source_location alias.
+  LogMessage& operator<<(const absl::SourceLocation& loc) {
+    OstreamView view(*data_);
+    view.stream() << loc.file_name() << ':' << loc.line();
+    return *this;
+  }
+
   // Handle stream manipulators e.g. std::endl.
   LogMessage& operator<<(std::ostream& (*absl_nonnull m)(std::ostream& os));
   LogMessage& operator<<(std::ios_base& (*absl_nonnull m)(std::ios_base& os));

absl/log/log_format_test.cc

@@ -41,6 +41,7 @@
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
+#include "absl/types/source_location.h"
 
 namespace {
 using ::absl::log_internal::AsString;
@@ -291,6 +292,21 @@ TYPED_TEST(SignedIntLogFormatTest, BitfieldNegative) {
   LOG(INFO) << value.bits;
 }
 
+TEST(SourceLocationTest, Format) {
+  absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
+  EXPECT_CALL(test_sink, Send).Times(0);
+
+  absl::SourceLocation loc = absl::SourceLocation::current();
+  std::string expected = absl::StrCat(__FILE__, ":", __LINE__ - 1);
+
+  EXPECT_CALL(test_sink, Send(AllOf(TextMessage(Eq(expected)),
+                                    ENCODED_MESSAGE(HasValues(ElementsAre(
+                                        ValueWithStr(Eq(expected))))))));
+
+  test_sink.StartCapturingLogs();
+  LOG(INFO) << loc;
+}
+
 // Ignore these test cases on GCC due to "is too small to hold all values ..."
 // warning.
 #if !defined(__GNUC__) || defined(__clang__)