Support compile-time format string compilation (module)

fmtlib · Jun 5, 2021 · 929f2ba · 929f2ba
1 parent bf07456
commit 929f2ba
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Showing 3 changed files with 24 additions and 10 deletions.
diff --git a/include/fmt/compile.h b/include/fmt/compile.h
@@ -11,7 +11,15 @@
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace detail {
+FMT_MODULE_EXPORT_BEGIN
+
+// compile-time support
+namespace ct {
+// A compile-time string which is compiled into fast formatting code.
+class compiled_string {};
+}  // namespace ct
+
+FMT_BEGIN_DETAIL_NAMESPACE
 
 // An output iterator that counts the number of objects written to it and
 // discards them.
@@ -137,11 +145,8 @@ class truncating_iterator<OutputIt, std::true_type>
   truncating_iterator& operator*() { return *this; }
 };
 
-// A compile-time string which is compiled into fast formatting code.
-class compiled_string {};
-
 template <typename S>
-struct is_compiled_string : std::is_base_of<compiled_string, S> {};
+struct is_compiled_string : std::is_base_of<fmt::ct::compiled_string, S> {};
 
 /**
   \rst
@@ -157,15 +162,14 @@ struct is_compiled_string : std::is_base_of<compiled_string, S> {};
   \endrst
  */
 #ifdef __cpp_if_constexpr
-#  define FMT_COMPILE(s) \
-    FMT_STRING_IMPL(s, fmt::detail::compiled_string, explicit)
+#  define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::ct::compiled_string, explicit)
 #else
 #  define FMT_COMPILE(s) FMT_STRING(s)
 #endif
 
 #if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
 template <typename Char, size_t N, fmt::ct::str<Char, N> Str>
-struct udl_compiled_string : compiled_string {
+struct udl_compiled_string : fmt::ct::compiled_string {
   using char_type = Char;
   constexpr operator basic_string_view<char_type>() const {
     return {Str.data, N - 1};
@@ -527,9 +531,8 @@ constexpr auto compile(S format_str) {
   }
 }
 #endif  // __cpp_if_constexpr
-}  // namespace detail
 
-FMT_MODULE_EXPORT_BEGIN
+FMT_END_DETAIL_NAMESPACE
 
 #ifdef __cpp_if_constexpr
 

diff --git a/include/fmt/fmt.h b/include/fmt/fmt.h
@@ -23,6 +23,7 @@
   }()
 
 #define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::compile_string, )
+#define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::ct::compiled_string, explicit)
 
 import fmt;
 

diff --git a/test/module-test.cc b/test/module-test.cc
@@ -277,6 +277,8 @@ TEST(module_test, literals) {
   EXPECT_EQ("42", "{}"_format(42));
   EXPECT_EQ(L"42", fmt::format(L"{answer}", L"answer"_a = 42));
   EXPECT_EQ(L"42", L"{}"_format(42));
+  EXPECT_EQ("", fmt::format(""_cf));
+  EXPECT_EQ("42", fmt::format("{}"_cf, 42));
 }
 
 TEST(module_test, locale) {
@@ -565,3 +567,11 @@ TEST(module_test, compile_time_string) {
   fmt::vformat_to(wbuffer, FMT_STRING(L"{:}"), fmt::make_wformat_args(42));
   EXPECT_EQ(L"42", std::wstring_view(wbuffer));
 }
+
+TEST(module_test, compile_format_string) {
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{0:x}"), 0x42));
+  EXPECT_EQ(L"42", fmt::format(FMT_COMPILE(L"{:}"), 42));
+  using namespace fmt::literals;
+  EXPECT_EQ("4.2", fmt::format(FMT_COMPILE("{arg:3.1f}"), "arg"_a = 4.2));
+  EXPECT_EQ(L" 42", fmt::format(FMT_COMPILE(L"{arg:>3}"), L"arg"_a = L"42"));
+}