Add support for std::string_view in StrCat even when

absl::string_view != std::string_view.

PiperOrigin-RevId: 704802270
Change-Id: I8293f755a688707db575f0df22440f24ffad430e

absl/strings/BUILD.bazel

@@ -1118,6 +1118,7 @@ cc_test(
     deps = [
         ":str_format",
         ":strings",
+        "//absl/base:config",
         "@com_google_googletest//:gtest",
         "@com_google_googletest//:gtest_main",
     ],

absl/strings/CMakeLists.txt

@@ -371,6 +371,7 @@ absl_cc_test(
   DEPS
     absl::strings
     absl::str_format
+    absl::config
     absl::core_headers
     GTest::gmock_main
 )

absl/strings/str_cat.h

@@ -101,6 +101,7 @@
 #include <vector>
 
 #include "absl/base/attributes.h"
+#include "absl/base/config.h"
 #include "absl/base/nullability.h"
 #include "absl/base/port.h"
 #include "absl/meta/type_traits.h"
@@ -110,6 +111,10 @@
 #include "absl/strings/numbers.h"
 #include "absl/strings/string_view.h"
 
+#if defined(ABSL_HAVE_STD_STRING_VIEW) && !defined(ABSL_USES_STD_STRING_VIEW)
+#include <string_view>
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
@@ -361,6 +366,12 @@ class AlphaNum {
                ABSL_ATTRIBUTE_LIFETIME_BOUND)
       : piece_(pc) {}
 
+#if defined(ABSL_HAVE_STD_STRING_VIEW) && !defined(ABSL_USES_STD_STRING_VIEW)
+  AlphaNum(std::string_view pc  // NOLINT(runtime/explicit)
+               ABSL_ATTRIBUTE_LIFETIME_BOUND)
+      : piece_(pc.data(), pc.size()) {}
+#endif  // !ABSL_USES_STD_STRING_VIEW
+
   template <typename T, typename = typename std::enable_if<
                             HasAbslStringify<T>::value>::type>
   AlphaNum(  // NOLINT(runtime/explicit)

absl/strings/str_cat_test.cc

@@ -24,9 +24,14 @@
 #include <vector>
 
 #include "gtest/gtest.h"
+#include "absl/base/config.h"
 #include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 
+#if defined(ABSL_HAVE_STD_STRING_VIEW)
+#include <string_view>
+#endif
+
 #ifdef __ANDROID__
 // Android assert messages only go to system log, so death tests cannot inspect
 // the message for matching.
@@ -214,6 +219,14 @@ TEST(StrCat, CornerCases) {
   EXPECT_EQ(result, "");
 }
 
+#if defined(ABSL_HAVE_STD_STRING_VIEW)
+TEST(StrCat, StdStringView) {
+  std::string_view pieces[] = {"Hello", ", ", "World", "!"};
+  EXPECT_EQ(absl::StrCat(pieces[0], pieces[1], pieces[2], pieces[3]),
+                         "Hello, World!");
+}
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
 TEST(StrCat, NullConstCharPtr) {
   const char* null = nullptr;
   EXPECT_EQ(absl::StrCat("mon", null, "key"), "monkey");