// Formatting library for C++ - std::ostream support tests
//
// Copyright (c) 2012 - present, Victor Zverovich
// All rights reserved.
// For the license information refer to format.h.
#include <fstream>
#include "fmt/format.h"
using fmt::runtime;
struct test {};
// Test that there is no issues with specializations when fmt/ostream.h is
// included after fmt/format.h.
namespace fmt {
template <> struct formatter<test> : formatter<int> {
auto format(const test&, format_context& ctx) -> decltype(ctx.out()) {
return formatter<int>::format(42, ctx);
}
};
} // namespace fmt
#include <sstream>
#include "fmt/compile.h"
#include "fmt/ostream.h"
#include "fmt/ranges.h"
#include "gmock/gmock.h"
#include "gtest-extra.h"
#include "util.h"
auto operator<<(std::ostream& os, const date& d) -> std::ostream& {
os << d.year() << '-' << d.month() << '-' << d.day();
return os;
auto operator<<(std::wostream& os, const date& d) -> std::wostream& {
os << d.year() << L'-' << d.month() << L'-' << d.day();
// Make sure that overloaded comma operators do no harm to is_streamable.
struct type_with_comma_op {};
template <typename T> void operator,(type_with_comma_op, const T&);
template <typename T> type_with_comma_op operator<<(T&, const date&);
enum streamable_enum {};
auto operator<<(std::ostream& os, streamable_enum) -> std::ostream& {
return os << "streamable_enum";
enum unstreamable_enum {};
auto format_as(unstreamable_enum e) -> int { return e; }
struct empty_test {};
auto operator<<(std::ostream& os, empty_test) -> std::ostream& {
return os << "";
template <> struct formatter<test_string> : ostream_formatter {};
template <> struct formatter<date> : ostream_formatter {};
template <> struct formatter<streamable_enum> : ostream_formatter {};
template <> struct formatter<empty_test> : ostream_formatter {};
TEST(ostream_test, enum) {
EXPECT_EQ("streamable_enum", fmt::format("{}", streamable_enum()));
EXPECT_EQ("0", fmt::format("{}", unstreamable_enum()));
TEST(ostream_test, format) {
EXPECT_EQ("a string", fmt::format("{0}", test_string("a string")));
EXPECT_EQ("The date is 2012-12-9",
fmt::format("The date is {0}", date(2012, 12, 9)));
TEST(ostream_test, format_specs) {
using fmt::format_error;
EXPECT_EQ("def ", fmt::format("{0:<5}", test_string("def")));
EXPECT_EQ(" def", fmt::format("{0:>5}", test_string("def")));
EXPECT_EQ(" def ", fmt::format("{0:^5}", test_string("def")));
EXPECT_EQ("def**", fmt::format("{0:*<5}", test_string("def")));
EXPECT_THROW_MSG((void)fmt::format(runtime("{0:+}"), test_string()),
format_error, "format specifier requires numeric argument");
EXPECT_THROW_MSG((void)fmt::format(runtime("{0:-}"), test_string()),
EXPECT_THROW_MSG((void)fmt::format(runtime("{0: }"), test_string()),
EXPECT_THROW_MSG((void)fmt::format(runtime("{0:#}"), test_string()),
EXPECT_THROW_MSG((void)fmt::format(runtime("{0:05}"), test_string()),
EXPECT_EQ("test ", fmt::format("{0:13}", test_string("test")));
EXPECT_EQ("test ", fmt::format("{0:{1}}", test_string("test"), 13));
EXPECT_EQ("te", fmt::format("{0:.2}", test_string("test")));
EXPECT_EQ("te", fmt::format("{0:.{1}}", test_string("test"), 2));
TEST(ostream_test, empty_custom_output) {
EXPECT_EQ("", fmt::format("{}", empty_test()));
TEST(ostream_test, print) {
std::ostringstream os;
fmt::print(os, "Don't {}!", "panic");
EXPECT_EQ("Don't panic!", os.str());
TEST(ostream_test, write_to_ostream) {
fmt::memory_buffer buffer;
const char* foo = "foo";
buffer.append(foo, foo + std::strlen(foo));
fmt::detail::write_buffer(os, buffer);
EXPECT_EQ("foo", os.str());
TEST(ostream_test, write_to_ostream_max_size) {
auto max_size = fmt::detail::max_value<size_t>();
auto max_streamsize = fmt::detail::max_value<std::streamsize>();
if (max_size <= fmt::detail::to_unsigned(max_streamsize)) return;
struct test_buffer final : fmt::detail::buffer<char> {
explicit test_buffer(size_t size)
: fmt::detail::buffer<char>(nullptr, size, size) {}
void grow(size_t) override {}
} buffer(max_size);
struct mock_streambuf : std::streambuf {
MOCK_METHOD2(xsputn, std::streamsize(const void* s, std::streamsize n));
auto xsputn(const char* s, std::streamsize n) -> std::streamsize override {
const void* v = s;
return xsputn(v, n);
} streambuf;
struct test_ostream : std::ostream {
explicit test_ostream(mock_streambuf& output_buffer)
: std::ostream(&output_buffer) {}
} os(streambuf);
testing::InSequence sequence;
const char* data = nullptr;
using ustreamsize = std::make_unsigned<std::streamsize>::type;
ustreamsize size = max_size;
do {
auto n = std::min(size, fmt::detail::to_unsigned(max_streamsize));
EXPECT_CALL(streambuf, xsputn(data, static_cast<std::streamsize>(n)))
.WillOnce(testing::Return(max_streamsize));
data += n;
size -= n;
} while (size != 0);
TEST(ostream_test, join) {
int v[3] = {1, 2, 3};
EXPECT_EQ("1, 2, 3", fmt::format("{}", fmt::join(v, v + 3, ", ")));
TEST(ostream_test, join_fallback_formatter) {
auto strs = std::vector<test_string>{test_string("foo"), test_string("bar")};
EXPECT_EQ("foo, bar", fmt::format("{}", fmt::join(strs, ", ")));
#if FMT_USE_CONSTEXPR
TEST(ostream_test, constexpr_string) {
EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), std::string("42")));
EXPECT_EQ("a string",
fmt::format(FMT_STRING("{0}"), test_string("a string")));
#endif
namespace fmt_test {
struct abc {};
template <typename Output> auto operator<<(Output& out, abc) -> Output& {
return out << "abc";
} // namespace fmt_test
template <typename T> struct test_template {};
template <typename T>
auto operator<<(std::ostream& os, test_template<T>) -> std::ostream& {
return os << 1;
template <typename T> struct formatter<test_template<T>> : formatter<int> {
auto format(test_template<T>, format_context& ctx) -> decltype(ctx.out()) {
return formatter<int>::format(2, ctx);
template <> struct formatter<fmt_test::abc> : ostream_formatter {};
TEST(ostream_test, template) {
EXPECT_EQ("2", fmt::format("{}", test_template<int>()));
TEST(ostream_test, format_to_n) {
char buffer[4];
buffer[3] = 'x';
auto result = fmt::format_to_n(buffer, 3, "{}", fmt_test::abc());
EXPECT_EQ(3u, result.size);
EXPECT_EQ(buffer + 3, result.out);
EXPECT_EQ("abcx", fmt::string_view(buffer, 4));
result = fmt::format_to_n(buffer, 3, "x{}y", fmt_test::abc());
EXPECT_EQ(5u, result.size);
EXPECT_EQ("xabx", fmt::string_view(buffer, 4));
template <typename T> struct convertible {
T value;
explicit convertible(const T& val) : value(val) {}
operator T() const { return value; }
TEST(ostream_test, disable_builtin_ostream_operators) {
EXPECT_EQ("42", fmt::format("{:d}", convertible<unsigned short>(42)));
EXPECT_EQ("foo", fmt::format("{}", convertible<const char*>("foo")));
struct streamable_and_convertible_to_bool {
operator bool() const { return true; }
std::ostream& operator<<(std::ostream& os, streamable_and_convertible_to_bool) {
return os << "foo";
TEST(ostream_test, format_convertible_to_bool) {
// operator<< is intentionally not used because of potential ODR violations.
EXPECT_EQ(fmt::format("{}", streamable_and_convertible_to_bool()), "true");
struct streamable_and_convertible_to_string_view {
operator fmt::string_view() const { return "foo"; }
std::ostream& operator<<(std::ostream& os,
streamable_and_convertible_to_string_view) {
return os << "bar";
TEST(ostream_test, format_convertible_to_string_vew) {
EXPECT_EQ(fmt::format("{}", streamable_and_convertible_to_string_view()),
"foo");
struct copyfmt_test {};
std::ostream& operator<<(std::ostream& os, copyfmt_test) {
std::ios ios(nullptr);
ios.copyfmt(os);
template <> struct formatter<copyfmt_test> : ostream_formatter {};
TEST(ostream_test, copyfmt) {
EXPECT_EQ("foo", fmt::format("{}", copyfmt_test()));
TEST(ostream_test, to_string) {
EXPECT_EQ("abc", fmt::to_string(fmt_test::abc()));
TEST(ostream_test, range) {
EXPECT_EQ("[foo, bar]", fmt::format("{}", strs));
struct abstract {
virtual ~abstract() = default;
virtual void f() = 0;
friend auto operator<<(std::ostream& os, const abstract&) -> std::ostream& {
template <> struct formatter<abstract> : ostream_formatter {};
void format_abstract_compiles(const abstract& a) {
fmt::format(FMT_COMPILE("{}"), a);
TEST(ostream_test, is_formattable) {
EXPECT_TRUE(fmt::is_formattable<std::string>());
EXPECT_TRUE(fmt::is_formattable<fmt::detail::std_string_view<char>>());
struct streamable_and_unformattable {};
auto operator<<(std::ostream& os, streamable_and_unformattable)
-> std::ostream& {
TEST(ostream_test, streamed) {
EXPECT_FALSE(fmt::is_formattable<streamable_and_unformattable>());
EXPECT_EQ(fmt::format("{}", fmt::streamed(streamable_and_unformattable())),
TEST(ostream_test, closed_ofstream) {
std::ofstream ofs;
fmt::print(ofs, "discard");