Add support for ranges of types without formatters to join (#2262)

fmtlib · May 5, 2021 · 0ab30ee · 0ab30ee
1 parent 4f0eadf
commit 0ab30ee
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Showing 2 changed files with 24 additions and 7 deletions.
diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -3633,9 +3633,23 @@ template <typename It, typename Sentinel, typename Char>
 struct formatter<arg_join<It, Sentinel, Char>, Char> {
  private:
   using value_type = typename std::iterator_traits<It>::value_type;
+  using context = buffer_context<Char>;
+  using mapper = detail::arg_mapper<context>;
+
+  template <typename T, FMT_ENABLE_IF(has_formatter<T, context>::value)>
+  static auto map(const T& value) -> const T& {
+    return value;
+  }
+  template <typename T, FMT_ENABLE_IF(!has_formatter<T, context>::value)>
+  static auto map(const T& value) -> decltype(mapper().map(value)) {
+    return mapper().map(value);
+  }
+
   using formatter_type =
-      conditional_t<has_formatter<value_type, buffer_context<Char>>::value,
-                    formatter<value_type, Char>,
+      conditional_t<is_formattable<value_type>::value,
+                    formatter<remove_cvref_t<decltype(
+                                  map(std::declval<const value_type&>()))>,
+                              Char>,
                     detail::fallback_formatter<value_type, Char>>;
 
   formatter_type value_formatter_;
@@ -3652,11 +3666,11 @@ struct formatter<arg_join<It, Sentinel, Char>, Char> {
     auto it = value.begin;
     auto out = ctx.out();
     if (it != value.end) {
-      out = value_formatter_.format(*it++, ctx);
+      out = value_formatter_.format(map(*it++), ctx);
       while (it != value.end) {
         out = detail::copy_str<Char>(value.sep.begin(), value.sep.end(), out);
         ctx.advance_to(out);
-        out = value_formatter_.format(*it++, ctx);
+        out = value_formatter_.format(map(*it++), ctx);
       }
     }
     return out;

diff --git a/test/format-test.cc b/test/format-test.cc
@@ -1609,6 +1609,8 @@ TEST(format_test, bytes) {
   EXPECT_EQ(10, s.size());
 }
 
+enum test_enum { zero, one };
+
 TEST(format_test, join) {
   using fmt::join;
   int v1[3] = {1, 2, 3};
@@ -1632,6 +1634,9 @@ TEST(format_test, join) {
 
   EXPECT_EQ("(1, 2, 3)", fmt::format("({})", join(v1, ", ")));
   EXPECT_EQ("(+01.20, +03.40)", fmt::format("({:+06.2f})", join(v2, ", ")));
+
+  auto v4 = std::vector<test_enum>{zero, one, zero};
+  EXPECT_EQ("0 1 0", fmt::format("{}", join(v4, " ")));
 }
 
 #ifdef __cpp_lib_byte
@@ -1763,9 +1768,7 @@ TEST(format_test, udl_pass_user_defined_object_as_lvalue) {
 }
 #endif  // FMT_USE_USER_DEFINED_LITERALS
 
-enum test_enum { A };
-
-TEST(format_test, enum) { EXPECT_EQ("0", fmt::format("{}", A)); }
+TEST(format_test, enum) { EXPECT_EQ("0", fmt::format("{}", zero)); }
 
 TEST(format_test, formatter_not_specialized) {
   static_assert(!fmt::has_formatter<fmt::formatter<test_enum>,