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Simplify the fallback printing logic to have a single sequence of trial printers.

PiperOrigin-RevId: 298621376
pull/2350/head
Abseil Team 5 years ago committed by vslashg
parent 3de76551e0
commit 0bf8ea3065
2 changed files with 160 additions and 259 deletions
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  1. 413
      googletest/include/gtest/gtest-printers.h
  2. 6
      googletest/src/gtest-printers.cc

413
googletest/include/gtest/gtest-printers.h
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@ -119,53 +119,126 @@
namespace testing {
// Definitions in the 'internal' and 'internal2' name spaces are
// subject to change without notice. DO NOT USE THEM IN USER CODE!
namespace internal2 {
// Definitions in the internal* namespaces are subject to change without notice.
// DO NOT USE THEM IN USER CODE!
namespace internal {
// Prints the given number of bytes in the given object to the given
// ostream.
GTEST_API_ void PrintBytesInObjectTo(const unsigned char* obj_bytes,
size_t count,
::std::ostream* os);
template <typename T>
void UniversalPrint(const T& value, ::std::ostream* os);
// For selecting which printer to use when a given type has neither <<
// nor PrintTo().
enum TypeKind {
kProtobuf, // a protobuf type
kConvertibleToInteger, // a type implicitly convertible to BiggestInt
// (e.g. a named or unnamed enum type)
#if GTEST_INTERNAL_HAS_STRING_VIEW
kConvertibleToStringView, // a type implicitly convertible to
// absl::string_view or std::string_view
#endif
kOtherType // anything else
// Used to print an STL-style container when the user doesn't define
// a PrintTo() for it.
struct ContainerPrinter {
template <typename T,
typename = typename std::enable_if<
(sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
!IsRecursiveContainer<T>::value>::type>
static void PrintValue(const T& container, std::ostream* os) {
const size_t kMaxCount = 32; // The maximum number of elements to print.
*os << '{';
size_t count = 0;
for (auto&& elem : container) {
if (count > 0) {
*os << ',';
if (count == kMaxCount) { // Enough has been printed.
*os << " ...";
break;
}
}
*os << ' ';
// We cannot call PrintTo(elem, os) here as PrintTo() doesn't
// handle `elem` being a native array.
internal::UniversalPrint(elem, os);
++count;
}
if (count > 0) {
*os << ' ';
}
*os << '}';
}
};
// TypeWithoutFormatter<T, kTypeKind>::PrintValue(value, os) is called
// by the universal printer to print a value of type T when neither
// operator<< nor PrintTo() is defined for T, where kTypeKind is the
// "kind" of T as defined by enum TypeKind.
template <typename T, TypeKind kTypeKind>
class TypeWithoutFormatter {
public:
// This default version is called when kTypeKind is kOtherType.
static void PrintValue(const T& value, ::std::ostream* os) {
PrintBytesInObjectTo(
static_cast<const unsigned char*>(
reinterpret_cast<const void*>(std::addressof(value))),
sizeof(value), os);
// Used to print a pointer that is neither a char pointer nor a member
// pointer, when the user doesn't define PrintTo() for it. (A member
// variable pointer or member function pointer doesn't really point to
// a location in the address space. Their representation is
// implementation-defined. Therefore they will be printed as raw
// bytes.)
struct FunctionPointerPrinter {
template <typename T, typename = typename std::enable_if<
std::is_function<T>::value>::type>
static void PrintValue(T* p, ::std::ostream* os) {
if (p == nullptr) {
*os << "NULL";
} else {
// T is a function type, so '*os << p' doesn't do what we want
// (it just prints p as bool). We want to print p as a const
// void*.
*os << reinterpret_cast<const void*>(p);
}
}
};
// We print a protobuf using its ShortDebugString() when the string
// doesn't exceed this many characters; otherwise we print it using
// DebugString() for better readability.
const size_t kProtobufOneLinerMaxLength = 50;
struct PointerPrinter {
template <typename T>
static void PrintValue(T* p, ::std::ostream* os) {
if (p == nullptr) {
*os << "NULL";
} else {
// T is not a function type. We just call << to print p,
// relying on ADL to pick up user-defined << for their pointer
// types, if any.
*os << p;
}
}
};
namespace internal_stream {
struct Sentinel;
template <typename Char, typename CharTraits, typename T>
Sentinel* operator<<(::std::basic_ostream<Char, CharTraits>& os, const T& x);
// Check if the user has a user-defined operator<< for their type.
//
// We put this in its own namespace to inject a custom operator<< that allows us
// to probe the type's operator.
//
// Note that this operator<< takes a generic std::basic_ostream<Char,
// CharTraits> type instead of the more restricted std::ostream. If
// we define it to take an std::ostream instead, we'll get an
// "ambiguous overloads" compiler error when trying to print a type
// Foo that supports streaming to std::basic_ostream<Char,
// CharTraits>, as the compiler cannot tell whether
// operator<<(std::ostream&, const T&) or
// operator<<(std::basic_stream<Char, CharTraits>, const Foo&) is more
// specific.
template <typename T>
class TypeWithoutFormatter<T, kProtobuf> {
public:
constexpr bool UseStreamOperator() {
return !std::is_same<decltype(std::declval<std::ostream&>()
<< std::declval<const T&>()),
Sentinel*>::value;
}
} // namespace internal_stream
struct StreamPrinter {
template <typename T, typename = typename std::enable_if<
internal_stream::UseStreamOperator<T>()>::type>
static void PrintValue(const T& value, ::std::ostream* os) {
*os << value;
}
};
struct ProtobufPrinter {
// We print a protobuf using its ShortDebugString() when the string
// doesn't exceed this many characters; otherwise we print it using
// DebugString() for better readability.
static const size_t kProtobufOneLinerMaxLength = 50;
template <typename T, typename = typename std::enable_if<
internal::IsAProtocolMessage<T>::value>::type>
static void PrintValue(const T& value, ::std::ostream* os) {
std::string pretty_str = value.ShortDebugString();
if (pretty_str.length() > kProtobufOneLinerMaxLength) {
@ -175,9 +248,7 @@ class TypeWithoutFormatter<T, kProtobuf> {
}
};
template <typename T>
class TypeWithoutFormatter<T, kConvertibleToInteger> {
public:
struct ConvertibleToIntegerPrinter {
// Since T has no << operator or PrintTo() but can be implicitly
// converted to BiggestInt, we print it as a BiggestInt.
//
@ -185,112 +256,64 @@ class TypeWithoutFormatter<T, kConvertibleToInteger> {
// case printing it as an integer is the desired behavior. In case
// T is not an enum, printing it as an integer is the best we can do
// given that it has no user-defined printer.
static void PrintValue(const T& value, ::std::ostream* os) {
const internal::BiggestInt kBigInt = value;
*os << kBigInt;
static void PrintValue(internal::BiggestInt value, ::std::ostream* os) {
*os << value;
}
};
struct ConvertibleToStringViewPrinter {
#if GTEST_INTERNAL_HAS_STRING_VIEW
template <typename T>
class TypeWithoutFormatter<T, kConvertibleToStringView> {
public:
// Since T has neither operator<< nor PrintTo() but can be implicitly
// converted to absl::string_view, we print it as a absl::string_view
// (or std::string_view).
//
// Note: the implementation is further below, as it depends on
// internal::PrintTo symbol which is defined later in the file.
static void PrintValue(const T& value, ::std::ostream* os);
};
static void PrintValue(internal::StringView value, ::std::ostream* os) {
internal::UniversalPrint(value, os);
}
#endif
};
// Prints the given value to the given ostream. If the value is a
// protocol message, its debug string is printed; if it's an enum or
// of a type implicitly convertible to BiggestInt, it's printed as an
// integer; otherwise the bytes in the value are printed. This is
// what UniversalPrinter<T>::Print() does when it knows nothing about
// type T and T has neither << operator nor PrintTo().
//
// A user can override this behavior for a class type Foo by defining
// a << operator in the namespace where Foo is defined.
//
// We put this operator in namespace 'internal2' instead of 'internal'
// to simplify the implementation, as much code in 'internal' needs to
// use << in STL, which would conflict with our own << were it defined
// in 'internal'.
//
// Note that this operator<< takes a generic std::basic_ostream<Char,
// CharTraits> type instead of the more restricted std::ostream. If
// we define it to take an std::ostream instead, we'll get an
// "ambiguous overloads" compiler error when trying to print a type
// Foo that supports streaming to std::basic_ostream<Char,
// CharTraits>, as the compiler cannot tell whether
// operator<<(std::ostream&, const T&) or
// operator<<(std::basic_stream<Char, CharTraits>, const Foo&) is more
// specific.
template <typename Char, typename CharTraits, typename T>
::std::basic_ostream<Char, CharTraits>& operator<<(
::std::basic_ostream<Char, CharTraits>& os, const T& x) {
TypeWithoutFormatter<T, (internal::IsAProtocolMessage<T>::value
? kProtobuf
: std::is_convertible<
const T&, internal::BiggestInt>::value
? kConvertibleToInteger
:
#if GTEST_INTERNAL_HAS_STRING_VIEW
std::is_convertible<
const T&, internal::StringView>::value
? kConvertibleToStringView
:
#endif
kOtherType)>::PrintValue(x, &os);
return os;
}
} // namespace internal2
} // namespace testing
// Prints the given number of bytes in the given object to the given
// ostream.
GTEST_API_ void PrintBytesInObjectTo(const unsigned char* obj_bytes,
size_t count,
::std::ostream* os);
struct FallbackPrinter {
template <typename T>
static void PrintValue(const T& value, ::std::ostream* os) {
PrintBytesInObjectTo(
static_cast<const unsigned char*>(
reinterpret_cast<const void*>(std::addressof(value))),
sizeof(value), os);
}
};
// Try every printer in order and return the first one that works.
template <typename T, typename E, typename Printer, typename... Printers>
struct FindFirstPrinter : FindFirstPrinter<T, E, Printers...> {};
// This namespace MUST NOT BE NESTED IN ::testing, or the name look-up
// magic needed for implementing UniversalPrinter won't work.
namespace testing_internal {
template <typename T, typename Printer, typename... Printers>
struct FindFirstPrinter<
T, decltype(Printer::PrintValue(std::declval<const T&>(), nullptr)),
Printer, Printers...> {
using type = Printer;
};
// Used to print a value that is not an STL-style container when the
// user doesn't define PrintTo() for it.
// Select the best printer in the following order:
// - Print containers (they have begin/end/etc).
// - Print function pointers.
// - Print object pointers.
// - Use the stream operator, if available.
// - Print protocol buffers.
// - Print types convertible to BiggestInt.
// - Print types convertible to StringView, if available.
// - Fallback to printing the raw bytes of the object.
template <typename T>
void DefaultPrintNonContainerTo(const T& value, ::std::ostream* os) {
// With the following statement, during unqualified name lookup,
// testing::internal2::operator<< appears as if it was declared in
// the nearest enclosing namespace that contains both
// ::testing_internal and ::testing::internal2, i.e. the global
// namespace. For more details, refer to the C++ Standard section
// 7.3.4-1 [namespace.udir]. This allows us to fall back onto
// testing::internal2::operator<< in case T doesn't come with a <<
// operator.
using ::testing::internal2::operator<<;
// Assuming T is defined in namespace foo, in the next statement,
// the compiler will consider all of:
//
// 1. foo::operator<< (thanks to Koenig look-up),
// 2. ::operator<< (as the current namespace is enclosed in ::),
// 3. testing::internal2::operator<< (thanks to the using statement above).
//
// The operator<< whose type matches T best will be picked.
//
// We deliberately allow #2 to be a candidate, as sometimes it's
// impossible to define #1 (e.g. when foo is ::std, defining
// anything in it is undefined behavior unless you are a compiler
// vendor.).
*os << value;
void PrintWithFallback(const T& value, ::std::ostream* os) {
using Printer = typename FindFirstPrinter<
T, void, ContainerPrinter, FunctionPointerPrinter, PointerPrinter,
StreamPrinter, ProtobufPrinter, ConvertibleToIntegerPrinter,
ConvertibleToStringViewPrinter, FallbackPrinter>::type;
Printer::PrintValue(value, os);
}
} // namespace testing_internal
namespace testing {
namespace internal {
// FormatForComparison<ToPrint, OtherOperand>::Format(value) formats a
// value of type ToPrint that is an operand of a comparison assertion
// (e.g. ASSERT_EQ). OtherOperand is the type of the other operand in
@ -388,85 +411,6 @@ std::string FormatForComparisonFailureMessage(
template <typename T>
class UniversalPrinter;
template <typename T>
void UniversalPrint(const T& value, ::std::ostream* os);
enum DefaultPrinterType {
kPrintContainer,
kPrintPointer,
kPrintFunctionPointer,
kPrintOther,
};
template <DefaultPrinterType type> struct WrapPrinterType {};
// Used to print an STL-style container when the user doesn't define
// a PrintTo() for it.
template <typename C>
void DefaultPrintTo(WrapPrinterType<kPrintContainer> /* dummy */,
const C& container, ::std::ostream* os) {
const size_t kMaxCount = 32; // The maximum number of elements to print.
*os << '{';
size_t count = 0;
for (typename C::const_iterator it = container.begin();
it != container.end(); ++it, ++count) {
if (count > 0) {
*os << ',';
if (count == kMaxCount) { // Enough has been printed.
*os << " ...";
break;
}
}
*os << ' ';
// We cannot call PrintTo(*it, os) here as PrintTo() doesn't
// handle *it being a native array.
internal::UniversalPrint(*it, os);
}
if (count > 0) {
*os << ' ';
}
*os << '}';
}
// Used to print a pointer that is neither a char pointer nor a member
// pointer, when the user doesn't define PrintTo() for it. (A member
// variable pointer or member function pointer doesn't really point to
// a location in the address space. Their representation is
// implementation-defined. Therefore they will be printed as raw
// bytes.)
template <typename T>
void DefaultPrintTo(WrapPrinterType<kPrintPointer> /* dummy */,
T* p, ::std::ostream* os) {
if (p == nullptr) {
*os << "NULL";
} else {
// T is not a function type. We just call << to print p,
// relying on ADL to pick up user-defined << for their pointer
// types, if any.
*os << p;
}
}
template <typename T>
void DefaultPrintTo(WrapPrinterType<kPrintFunctionPointer> /* dummy */,
T* p, ::std::ostream* os) {
if (p == nullptr) {
*os << "NULL";
} else {
// T is a function type, so '*os << p' doesn't do what we want
// (it just prints p as bool). We want to print p as a const
// void*.
*os << reinterpret_cast<const void*>(p);
}
}
// Used to print a non-container, non-pointer value when the user
// doesn't define PrintTo() for it.
template <typename T>
void DefaultPrintTo(WrapPrinterType<kPrintOther> /* dummy */,
const T& value, ::std::ostream* os) {
::testing_internal::DefaultPrintNonContainerTo(value, os);
}
// Prints the given value using the << operator if it has one;
// otherwise prints the bytes in it. This is what
// UniversalPrinter<T>::Print() does when PrintTo() is not specialized
@ -480,36 +424,7 @@ void DefaultPrintTo(WrapPrinterType<kPrintOther> /* dummy */,
// wants).
template <typename T>
void PrintTo(const T& value, ::std::ostream* os) {
// DefaultPrintTo() is overloaded. The type of its first argument
// determines which version will be picked.
//
// Note that we check for container types here, prior to we check
// for protocol message types in our operator<<. The rationale is:
//
// For protocol messages, we want to give people a chance to
// override Google Mock's format by defining a PrintTo() or
// operator<<. For STL containers, other formats can be
// incompatible with Google Mock's format for the container
// elements; therefore we check for container types here to ensure
// that our format is used.
//
// Note that MSVC and clang-cl do allow an implicit conversion from
// pointer-to-function to pointer-to-object, but clang-cl warns on it.
// So don't use ImplicitlyConvertible if it can be helped since it will
// cause this warning, and use a separate overload of DefaultPrintTo for
// function pointers so that the `*os << p` in the object pointer overload
// doesn't cause that warning either.
DefaultPrintTo(
WrapPrinterType <
(sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
!IsRecursiveContainer<T>::value
? kPrintContainer
: !std::is_pointer<T>::value
? kPrintOther
: std::is_function<typename std::remove_pointer<T>::type>::value
? kPrintFunctionPointer
: kPrintPointer > (),
value, os);
internal::PrintWithFallback(value, os);
}
// The following list of PrintTo() overloads tells
@ -900,16 +815,6 @@ Strings UniversalTersePrintTupleFieldsToStrings(const Tuple& value) {
} // namespace internal
#if GTEST_INTERNAL_HAS_STRING_VIEW
namespace internal2 {
template <typename T>
void TypeWithoutFormatter<T, kConvertibleToStringView>::PrintValue(
const T& value, ::std::ostream* os) {
internal::PrintTo(internal::StringView(value), os);
}
} // namespace internal2
#endif
template <typename T>
::std::string PrintToString(const T& value) {
::std::stringstream ss;

6
googletest/src/gtest-printers.cc
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@ -104,7 +104,7 @@ void PrintBytesInObjectToImpl(const unsigned char* obj_bytes, size_t count,
} // namespace
namespace internal2 {
namespace internal {
// Delegates to PrintBytesInObjectToImpl() to print the bytes in the
// given object. The delegation simplifies the implementation, which
@ -116,10 +116,6 @@ void PrintBytesInObjectTo(const unsigned char* obj_bytes, size_t count,
PrintBytesInObjectToImpl(obj_bytes, count, os);
}
} // namespace internal2
namespace internal {
// Depending on the value of a char (or wchar_t), we print it in one
// of three formats:
// - as is if it's a printable ASCII (e.g. 'a', '2', ' '),

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