Export of internal Abseil changes

--
34c0d521b11ed4191ea3e071a864a84e5e5941b7 by Matthew Brown <matthewbr@google.com>:

Release absl::StrFormat custom type extensions
 - Allows StrFormat methods to be extended to accept types which implement
   AbslFormatConvert()
 - NOLINTNEXTLINE(readability-redundant-declaration) used, declarations are
   required in some compilers.

PiperOrigin-RevId: 316963065

--
4d475b5ad02d41057447d722ad35573fc4f48d1f by Evan Brown <ezb@google.com>:

Small fix to previous change: the first overload of insert_iterator_unique wasn't actually being selected. Fix that issue and add tests to verify that it actually works.

Note: couldn't use TestInstanceTracker here because that counts instances (and decrements in destructor) rather than counting all constructor calls.
PiperOrigin-RevId: 316927690
GitOrigin-RevId: 34c0d521b11ed4191ea3e071a864a84e5e5941b7
Change-Id: If8bbb8317b93af4084ac4cc55b752b99b1581b58

5 files changed, 82 insertions, 6 deletions

diff --git a/absl/strings/internal/str_format/arg.h b/absl/strings/internal/str_format/arg.h
index d441e87f..3dbc1526 100644
--- a/absl/strings/internal/str_format/arg.h
+++ b/absl/strings/internal/str_format/arg.h
@@ -25,10 +25,12 @@ class Cord;
 class FormatCountCapture;
 class FormatSink;
 
-namespace str_format_internal {
-
+template <absl::FormatConversionCharSet C>
+struct FormatConvertResult;
 class FormatConversionSpec;
 
+namespace str_format_internal {
+
 template <typename T, typename = void>
 struct HasUserDefinedConvert : std::false_type {};
 
@@ -39,6 +41,22 @@ struct HasUserDefinedConvert<T, void_t<decltype(AbslFormatConvert(
                                     std::declval<FormatSink*>()))>>
     : std::true_type {};
 
+void AbslFormatConvert();  // Stops the lexical name lookup
+template <typename T>
+auto FormatConvertImpl(const T& v, FormatConversionSpecImpl conv,
+                       FormatSinkImpl* sink)
+    -> decltype(AbslFormatConvert(v,
+                                  std::declval<const FormatConversionSpec&>(),
+                                  std::declval<FormatSink*>())) {
+  using FormatConversionSpecT =
+      absl::enable_if_t<sizeof(const T& (*)()) != 0, FormatConversionSpec>;
+  using FormatSinkT =
+      absl::enable_if_t<sizeof(const T& (*)()) != 0, FormatSink>;
+  auto fcs = conv.Wrap<FormatConversionSpecT>();
+  auto fs = sink->Wrap<FormatSinkT>();
+  return AbslFormatConvert(v, fcs, &fs);
+}
+
 template <typename T>
 class StreamedWrapper;
 
@@ -46,6 +64,13 @@ class StreamedWrapper;
 // then convert it, appending to `sink` and return `true`.
 // Otherwise fail and return `false`.
 
+// AbslFormatConvert(v, conv, sink) is intended to be found by ADL on 'v'
+// as an extension mechanism. These FormatConvertImpl functions are the default
+// implementations.
+// The ADL search is augmented via the 'Sink*' parameter, which also
+// serves as a disambiguator to reject possible unintended 'AbslFormatConvert'
+// functions in the namespaces associated with 'v'.
+
 // Raw pointers.
 struct VoidPtr {
   VoidPtr() = default;
@@ -62,6 +87,11 @@ struct ArgConvertResult {
 };
 
 template <FormatConversionCharSet C>
+constexpr FormatConversionCharSet ExtractCharSet(FormatConvertResult<C>) {
+  return C;
+}
+
+template <FormatConversionCharSet C>
 constexpr FormatConversionCharSet ExtractCharSet(ArgConvertResult<C>) {
   return C;
 }
diff --git a/absl/strings/internal/str_format/arg_test.cc b/absl/strings/internal/str_format/arg_test.cc
index bf3d7e8e..f53fd6bd 100644
--- a/absl/strings/internal/str_format/arg_test.cc
+++ b/absl/strings/internal/str_format/arg_test.cc
@@ -23,8 +23,17 @@ class FormatArgImplTest : public ::testing::Test {
   enum Color { kRed, kGreen, kBlue };
 
   static const char *hi() { return "hi"; }
+
+  struct X {};
+
+  X x_;
 };
 
+inline FormatConvertResult<FormatConversionCharSet{}> AbslFormatConvert(
+    const FormatArgImplTest::X &, const FormatConversionSpec &, FormatSink *) {
+  return {false};
+}
+
 TEST_F(FormatArgImplTest, ToInt) {
   int out = 0;
   EXPECT_TRUE(FormatArgImplFriend::ToInt(FormatArgImpl(1), &out));
@@ -59,6 +68,7 @@ TEST_F(FormatArgImplTest, ToInt) {
       FormatArgImpl(static_cast<int *>(nullptr)), &out));
   EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl(hi()), &out));
   EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl("hi"), &out));
+  EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl(x_), &out));
   EXPECT_TRUE(FormatArgImplFriend::ToInt(FormatArgImpl(kBlue), &out));
   EXPECT_EQ(2, out);
 }
diff --git a/absl/strings/internal/str_format/extension.cc b/absl/strings/internal/str_format/extension.cc
index 94f2b9c2..bb0d96cf 100644
--- a/absl/strings/internal/str_format/extension.cc
+++ b/absl/strings/internal/str_format/extension.cc
@@ -33,6 +33,29 @@ std::string Flags::ToString() const {
   return s;
 }
 
+#define ABSL_INTERNAL_X_VAL(id) \
+  constexpr absl::FormatConversionChar FormatConversionCharInternal::id;
+ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(ABSL_INTERNAL_X_VAL, )
+#undef ABSL_INTERNAL_X_VAL
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr absl::FormatConversionChar FormatConversionCharInternal::kNone;
+
+#define ABSL_INTERNAL_CHAR_SET_CASE(c) \
+  constexpr FormatConversionCharSet FormatConversionCharSetInternal::c;
+ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(ABSL_INTERNAL_CHAR_SET_CASE, )
+#undef ABSL_INTERNAL_CHAR_SET_CASE
+
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kStar;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kIntegral;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kFloating;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kNumeric;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kPointer;
+
 bool FormatSinkImpl::PutPaddedString(string_view value, int width,
                                      int precision, bool left) {
   size_t space_remaining = 0;
diff --git a/absl/strings/internal/str_format/extension.h b/absl/strings/internal/str_format/extension.h
index 6c60c6c3..a9b9e137 100644
--- a/absl/strings/internal/str_format/extension.h
+++ b/absl/strings/internal/str_format/extension.h
@@ -31,11 +31,11 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-namespace str_format_internal {
-
 enum class FormatConversionChar : uint8_t;
 enum class FormatConversionCharSet : uint64_t;
 
+namespace str_format_internal {
+
 class FormatRawSinkImpl {
  public:
   // Implicitly convert from any type that provides the hook function as
@@ -361,14 +361,12 @@ struct FormatConversionCharSetInternal {
   static constexpr FormatConversionCharSet kStar =
       FormatConversionCharToConvValue('*');
 
-  // Some predefined values (TODO(matthewbr), delete any that are unused).
   static constexpr FormatConversionCharSet kIntegral =
       FormatConversionCharSetUnion(d, i, u, o, x, X);
   static constexpr FormatConversionCharSet kFloating =
       FormatConversionCharSetUnion(a, e, f, g, A, E, F, G);
   static constexpr FormatConversionCharSet kNumeric =
       FormatConversionCharSetUnion(kIntegral, kFloating);
-  static constexpr FormatConversionCharSet kString = s;
   static constexpr FormatConversionCharSet kPointer = p;
 };
 
diff --git a/absl/strings/internal/str_format/extension_test.cc b/absl/strings/internal/str_format/extension_test.cc
index 0a023f9c..1c93fdb1 100644
--- a/absl/strings/internal/str_format/extension_test.cc
+++ b/absl/strings/internal/str_format/extension_test.cc
@@ -80,4 +80,19 @@ TEST(FormatExtensionTest, SinkAppendChars) {
     EXPECT_EQ(actual, expected);
   }
 }
+
+TEST(FormatExtensionTest, VerifyEnumEquality) {
+#define X_VAL(id)                           \
+  EXPECT_EQ(absl::FormatConversionChar::id, \
+            absl::str_format_internal::FormatConversionCharInternal::id);
+  ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(X_VAL, );
+#undef X_VAL
+
+#define X_VAL(id)                              \
+  EXPECT_EQ(absl::FormatConversionCharSet::id, \
+            absl::str_format_internal::FormatConversionCharSetInternal::id);
+  ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(X_VAL, );
+#undef X_VAL
+}
+
 }  // namespace