Reenable support for fallback formatter to join (#2040)

fmtlib · Dec 4, 2020 · 742abd6 · 742abd6
1 parent 33f9a6d
commit 742abd6
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Showing 3 changed files with 37 additions and 11 deletions.
diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -3719,24 +3719,32 @@ struct arg_join : detail::view {
       : begin(b), end(e), sep(s) {}
 };
 
+template <typename Formatter, typename It, typename Sentinel, typename Char,
+          typename FormatContext>
+auto format_join(Formatter& arg_formatter,
+                 const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
+    -> decltype(ctx.out()) {
+  auto it = value.begin;
+  auto out = ctx.out();
+  if (it != value.end) {
+    out = arg_formatter.format(*it++, ctx);
+    while (it != value.end) {
+      out = detail::copy_str<Char>(value.sep.begin(), value.sep.end(), out);
+      ctx.advance_to(out);
+      out = arg_formatter.format(*it++, ctx);
+    }
+  }
+  return out;
+}
+
 template <typename It, typename Sentinel, typename Char>
 struct formatter<arg_join<It, Sentinel, Char>, Char>
     : formatter<typename std::iterator_traits<It>::value_type, Char> {
   template <typename FormatContext>
   auto format(const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
       -> decltype(ctx.out()) {
     using base = formatter<typename std::iterator_traits<It>::value_type, Char>;
-    auto it = value.begin;
-    auto out = ctx.out();
-    if (it != value.end) {
-      out = base::format(*it++, ctx);
-      while (it != value.end) {
-        out = detail::copy_str<Char>(value.sep.begin(), value.sep.end(), out);
-        ctx.advance_to(out);
-        out = base::format(*it++, ctx);
-      }
-    }
-    return out;
+    return format_join(static_cast<base&>(*this), value, ctx);
   }
 };
 

diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
@@ -147,6 +147,19 @@ struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
     return std::copy(buffer.begin(), buffer.end(), ctx.out());
   }
 };
+
+template <typename It, typename Sentinel, typename Char>
+struct fallback_formatter<arg_join<It, Sentinel, Char>, Char>
+    : fallback_formatter<typename std::iterator_traits<It>::value_type, Char> {
+  template <typename FormatContext>
+  auto format(const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
+      -> decltype(ctx.out()) {
+    using base =
+        fallback_formatter<typename std::iterator_traits<It>::value_type, Char>;
+    return format_join(static_cast<base&>(*this), value, ctx);
+  }
+};
+
 }  // namespace detail
 
 template <typename Char>

diff --git a/test/ostream-test.cc b/test/ostream-test.cc
@@ -188,6 +188,11 @@ TEST(OStreamTest, Join) {
   EXPECT_EQ("1, 2, 3", fmt::format("{}", fmt::join(v, v + 3, ", ")));
 }
 
+TEST(OStreamTest, JoinFallbackFormatter) {
+  auto strs = std::vector<TestString>{TestString("foo"), TestString("bar")};
+  EXPECT_EQ("foo, bar", fmt::format("{}", fmt::join(strs, ", ")));
+}
+
 #if FMT_USE_CONSTEXPR
 TEST(OStreamTest, ConstexprString) {
   EXPECT_EQ("42", format(FMT_STRING("{}"), std::string("42")));