Print std::basic_string_view<Char> as a string literal

This is a followup to a previous change switching std::u8string,
std::u16string, and std::u32string to print as string literals instead
of an array of characters. Also update the PrintCharsAsStringTo<Char>()
helper to handle cases where the pointer to the string data is null;
unlike std::basic_string<Char>, std::basic_string_view<Char>'s data()
is allowed to return nullptr.

The new PrintTo overloads complicate the PrintTo(internal::StringView)
overload, which needs to be disabled if internal::StringView is an alias
for std::string_view to avoid multiple definitions with the same
overload. Simply omitting the unconditional PrintTo(std::string_view)
overload is a worse option though, as this results in std::string_view
not printing nicely if internal::StringView is not an alias for
std::string_view.
PiperOrigin-RevId: 762020327
Change-Id: I92f5bdbacba89e97bbcc0fef3ca9261ea5a788d3

Author: zetafunction

googletest/include/gtest/gtest-printers.h

@@ -111,6 +111,7 @@
 #include <ostream>  // NOLINT
 #include <sstream>
 #include <string>
+#include <string_view>
 #include <tuple>
 #include <type_traits>
 #include <typeinfo>
@@ -248,8 +249,8 @@ struct StreamPrinter {
   // ADL (possibly involving implicit conversions).
   // (Use SFINAE via return type, because it seems GCC < 12 doesn't handle name
   // lookup properly when we do it in the template parameter list.)
-  static auto PrintValue(const T& value,
-                         ::std::ostream* os) -> decltype((void)(*os << value)) {
+  static auto PrintValue(const T& value, ::std::ostream* os)
+      -> decltype((void)(*os << value)) {
     // Call streaming operator found by ADL, possibly with implicit conversions
     // of the arguments.
     *os << value;
@@ -702,44 +703,63 @@ void PrintRawArrayTo(const T a[], size_t count, ::std::ostream* os) {
   }
 }
 
-// Overloads for ::std::string.
-GTEST_API_ void PrintStringTo(const ::std::string& s, ::std::ostream* os);
+// Overloads for ::std::string and ::std::string_view
+GTEST_API_ void PrintStringTo(::std::string_view s, ::std::ostream* os);
 inline void PrintTo(const ::std::string& s, ::std::ostream* os) {
   PrintStringTo(s, os);
 }
+inline void PrintTo(::std::string_view s, ::std::ostream* os) {
+  PrintStringTo(s, os);
+}
 
-// Overloads for ::std::u8string
+// Overloads for ::std::u8string and ::std::u8string_view
 #ifdef __cpp_lib_char8_t
-GTEST_API_ void PrintU8StringTo(const ::std::u8string& s, ::std::ostream* os);
+GTEST_API_ void PrintU8StringTo(::std::u8string_view s, ::std::ostream* os);
 inline void PrintTo(const ::std::u8string& s, ::std::ostream* os) {
   PrintU8StringTo(s, os);
 }
+inline void PrintTo(::std::u8string_view s, ::std::ostream* os) {
+  PrintU8StringTo(s, os);
+}
 #endif
 
-// Overloads for ::std::u16string
-GTEST_API_ void PrintU16StringTo(const ::std::u16string& s, ::std::ostream* os);
+// Overloads for ::std::u16string and ::std::u16string_view
+GTEST_API_ void PrintU16StringTo(::std::u16string_view s, ::std::ostream* os);
 inline void PrintTo(const ::std::u16string& s, ::std::ostream* os) {
   PrintU16StringTo(s, os);
 }
+inline void PrintTo(::std::u16string_view s, ::std::ostream* os) {
+  PrintU16StringTo(s, os);
+}
 
-// Overloads for ::std::u32string
-GTEST_API_ void PrintU32StringTo(const ::std::u32string& s, ::std::ostream* os);
+// Overloads for ::std::u32string and ::std::u32string_view
+GTEST_API_ void PrintU32StringTo(::std::u32string_view s, ::std::ostream* os);
 inline void PrintTo(const ::std::u32string& s, ::std::ostream* os) {
   PrintU32StringTo(s, os);
 }
+inline void PrintTo(::std::u32string_view s, ::std::ostream* os) {
+  PrintU32StringTo(s, os);
+}
 
-// Overloads for ::std::wstring.
+// Overloads for ::std::wstring and ::std::wstring_view
 #if GTEST_HAS_STD_WSTRING
-GTEST_API_ void PrintWideStringTo(const ::std::wstring& s, ::std::ostream* os);
+GTEST_API_ void PrintWideStringTo(::std::wstring_view s, ::std::ostream* os);
 inline void PrintTo(const ::std::wstring& s, ::std::ostream* os) {
   PrintWideStringTo(s, os);
 }
+inline void PrintTo(::std::wstring_view s, ::std::ostream* os) {
+  PrintWideStringTo(s, os);
+}
 #endif  // GTEST_HAS_STD_WSTRING
 
 #if GTEST_INTERNAL_HAS_STRING_VIEW
-// Overload for internal::StringView.
+// Overload for internal::StringView. Needed for build configurations where
+// internal::StringView is an alias for absl::string_view, but absl::string_view
+// is a distinct type from std::string_view.
+template <int&... ExplicitArgumentBarrier, typename T = internal::StringView,
+          std::enable_if_t<!std::is_same_v<T, ::std::string_view>, int> = 0>
 inline void PrintTo(internal::StringView sp, ::std::ostream* os) {
-  PrintTo(::std::string(sp), os);
+  PrintStringTo(sp, os);
 }
 #endif  // GTEST_INTERNAL_HAS_STRING_VIEW
 

googletest/src/gtest-printers.cc

@@ -50,7 +50,7 @@
 #include <iomanip>
 #include <ios>
 #include <ostream>  // NOLINT
-#include <string>
+#include <string_view>
 #include <type_traits>
 
 #include "gtest/internal/gtest-port.h"
@@ -333,14 +333,14 @@ void PrintTo(__int128_t v, ::std::ostream* os) {
 
 // Prints the given array of characters to the ostream.  CharType must be either
 // char, char8_t, char16_t, char32_t, or wchar_t.
-// The array starts at begin, the length is len, it may include '\0' characters
-// and may not be NUL-terminated.
+// The array starts at begin (which may be nullptr) and contains len characters.
+// The array may include '\0' characters and may not be NUL-terminated.
 template <typename CharType>
 GTEST_ATTRIBUTE_NO_SANITIZE_MEMORY_ GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
     GTEST_ATTRIBUTE_NO_SANITIZE_HWADDRESS_
         GTEST_ATTRIBUTE_NO_SANITIZE_THREAD_ static CharFormat
         PrintCharsAsStringTo(const CharType* begin, size_t len, ostream* os) {
-  const char* const quote_prefix = GetCharWidthPrefix(*begin);
+  const char* const quote_prefix = GetCharWidthPrefix(CharType());
   *os << quote_prefix << "\"";
   bool is_previous_hex = false;
   CharFormat print_format = kAsIs;
@@ -522,7 +522,7 @@ void ConditionalPrintAsText(const char* str, size_t length, ostream* os) {
 
 }  // anonymous namespace
 
-void PrintStringTo(const ::std::string& s, ostream* os) {
+void PrintStringTo(::std::string_view s, ostream* os) {
   if (PrintCharsAsStringTo(s.data(), s.size(), os) == kHexEscape) {
     if (GTEST_FLAG_GET(print_utf8)) {
       ConditionalPrintAsText(s.data(), s.size(), os);
@@ -531,21 +531,21 @@ void PrintStringTo(const ::std::string& s, ostream* os) {
 }
 
 #ifdef __cpp_lib_char8_t
-void PrintU8StringTo(const ::std::u8string& s, ostream* os) {
+void PrintU8StringTo(::std::u8string_view s, ostream* os) {
   PrintCharsAsStringTo(s.data(), s.size(), os);
 }
 #endif
 
-void PrintU16StringTo(const ::std::u16string& s, ostream* os) {
+void PrintU16StringTo(::std::u16string_view s, ostream* os) {
   PrintCharsAsStringTo(s.data(), s.size(), os);
 }
 
-void PrintU32StringTo(const ::std::u32string& s, ostream* os) {
+void PrintU32StringTo(::std::u32string_view s, ostream* os) {
   PrintCharsAsStringTo(s.data(), s.size(), os);
 }
 
 #if GTEST_HAS_STD_WSTRING
-void PrintWideStringTo(const ::std::wstring& s, ostream* os) {
+void PrintWideStringTo(::std::wstring_view s, ostream* os) {
   PrintCharsAsStringTo(s.data(), s.size(), os);
 }
 #endif  // GTEST_HAS_STD_WSTRING

googletest/test/googletest-printers-test.cc

@@ -48,6 +48,7 @@
 #include <set>
 #include <sstream>
 #include <string>
+#include <string_view>
 #include <tuple>
 #include <unordered_map>
 #include <unordered_set>
@@ -65,7 +66,7 @@
 
 #if GTEST_INTERNAL_HAS_STD_SPAN
 #include <span>  // NOLINT
-#endif  // GTEST_INTERNAL_HAS_STD_SPAN
+#endif           // GTEST_INTERNAL_HAS_STD_SPAN
 
 #if GTEST_INTERNAL_HAS_COMPARE_LIB
 #include <compare>  // NOLINT
@@ -799,7 +800,7 @@ struct Foo {
 TEST(PrintPointerTest, MemberVariablePointer) {
   EXPECT_TRUE(HasPrefix(Print(&Foo::value),
                         Print(sizeof(&Foo::value)) + "-byte object "));
-  int Foo::*p = NULL;  // NOLINT
+  int Foo::* p = NULL;  // NOLINT
   EXPECT_TRUE(HasPrefix(Print(p), Print(sizeof(p)) + "-byte object "));
 }
 
@@ -926,7 +927,7 @@ TEST(PrintArrayTest, BigArray) {
             PrintArrayHelper(a));
 }
 
-// Tests printing ::string and ::std::string.
+// Tests printing ::std::string and ::string_view.
 
 // ::std::string.
 TEST(PrintStringTest, StringInStdNamespace) {
@@ -936,6 +937,13 @@ TEST(PrintStringTest, StringInStdNamespace) {
             Print(str));
 }
 
+TEST(PrintStringTest, StringViewInStdNamespace) {
+  const char s[] = "'\"?\\\a\b\f\n\0\r\t\v\x7F\xFF a";
+  const ::std::string_view str(s, sizeof(s));
+  EXPECT_EQ("\"'\\\"?\\\\\\a\\b\\f\\n\\0\\r\\t\\v\\x7F\\xFF a\\0\"",
+            Print(str));
+}
+
 TEST(PrintStringTest, StringAmbiguousHex) {
   // "\x6BANANA" is ambiguous, it can be interpreted as starting with either of:
   // '\x6', '\x6B', or '\x6BA'.
@@ -953,7 +961,7 @@ TEST(PrintStringTest, StringAmbiguousHex) {
   EXPECT_EQ("\"!\\x5-!\"", Print(::std::string("!\x5-!")));
 }
 
-// Tests printing ::std::wstring.
+// Tests printing ::std::wstring and ::std::wstring_view.
 #if GTEST_HAS_STD_WSTRING
 // ::std::wstring.
 TEST(PrintWideStringTest, StringInStdNamespace) {
@@ -965,6 +973,15 @@ TEST(PrintWideStringTest, StringInStdNamespace) {
       Print(str));
 }
 
+TEST(PrintWideStringTest, StringViewInStdNamespace) {
+  const wchar_t s[] = L"'\"?\\\a\b\f\n\0\r\t\v\xD3\x576\x8D3\xC74D a";
+  const ::std::wstring_view str(s, sizeof(s) / sizeof(wchar_t));
+  EXPECT_EQ(
+      "L\"'\\\"?\\\\\\a\\b\\f\\n\\0\\r\\t\\v"
+      "\\xD3\\x576\\x8D3\\xC74D a\\0\"",
+      Print(str));
+}
+
 TEST(PrintWideStringTest, StringAmbiguousHex) {
   // same for wide strings.
   EXPECT_EQ("L\"0\\x12\" L\"3\"", Print(::std::wstring(L"0\x12"
@@ -983,6 +1000,12 @@ TEST(PrintStringTest, U8String) {
   EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type.
   EXPECT_EQ("u8\"Hello, \\xE4\\xB8\\x96\\xE7\\x95\\x8C\"", Print(str));
 }
+
+TEST(PrintStringTest, U8StringView) {
+  std::u8string_view str = u8"Hello, 世界";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type.
+  EXPECT_EQ("u8\"Hello, \\xE4\\xB8\\x96\\xE7\\x95\\x8C\"", Print(str));
+}
 #endif
 
 TEST(PrintStringTest, U16String) {
@@ -991,12 +1014,24 @@ TEST(PrintStringTest, U16String) {
   EXPECT_EQ("u\"Hello, \\x4E16\\x754C\"", Print(str));
 }
 
+TEST(PrintStringTest, U16StringView) {
+  std::u16string_view str = u"Hello, 世界";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type.
+  EXPECT_EQ("u\"Hello, \\x4E16\\x754C\"", Print(str));
+}
+
 TEST(PrintStringTest, U32String) {
   std::u32string str = U"Hello, 🗺️";
   EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type
   EXPECT_EQ("U\"Hello, \\x1F5FA\\xFE0F\"", Print(str));
 }
 
+TEST(PrintStringTest, U32StringView) {
+  std::u32string_view str = U"Hello, 🗺️";
+  EXPECT_EQ(str, str);  // Verify EXPECT_EQ compiles with this type
+  EXPECT_EQ("U\"Hello, \\x1F5FA\\xFE0F\"", Print(str));
+}
+
 // Tests printing types that support generic streaming (i.e. streaming
 // to std::basic_ostream<Char, CharTraits> for any valid Char and
 // CharTraits types).
@@ -1456,7 +1491,7 @@ TEST(PrintReferenceTest, HandlesMemberFunctionPointer) {
 // Tests that the universal printer prints a member variable pointer
 // passed by reference.
 TEST(PrintReferenceTest, HandlesMemberVariablePointer) {
-  int Foo::*p = &Foo::value;  // NOLINT
+  int Foo::* p = &Foo::value;  // NOLINT
   EXPECT_TRUE(HasPrefix(PrintByRef(p), "@" + PrintPointer(&p) + " " +
                                            Print(sizeof(p)) + "-byte object "));
 }