From b69e6dcead82f0e15751346ee2c3aadfcbfde9a5 Mon Sep 17 00:00:00 2001
From: vitaut <victor.zverovich@gmail.com>
Date: Tue, 19 Apr 2016 08:56:31 -0700
Subject: [PATCH] Make BasicArgFormatter public and add ArgFormatter

This allows providing custom argument formatters without relying on
internal APIs (#235).
---
 cppformat/format.h  | 59 +++++++++++++++++++++++++--------------------
 test/format-test.cc | 18 +++++++++++++-
 2 files changed, 50 insertions(+), 27 deletions(-)

diff --git a/cppformat/format.h b/cppformat/format.h
index 4e26d828..ccd928fc 100644
--- a/cppformat/format.h
+++ b/cppformat/format.h
@@ -372,17 +372,15 @@ class BasicWriter;
 typedef BasicWriter<char> Writer;
 typedef BasicWriter<wchar_t> WWriter;
 
-namespace internal {
 template <typename Char>
-class BasicArgFormatter;
-}
+class ArgFormatter;
 
 template <typename CharType,
-          typename ArgFormatter = internal::BasicArgFormatter<CharType> >
+          typename ArgFormatter = fmt::ArgFormatter<CharType> >
 class BasicFormatter;
 
-template <typename Char, typename T>
-void format(BasicFormatter<Char> &f, const Char *&format_str, const T &value);
+template <typename Char, typename ArgFormatter, typename T>
+void format(BasicFormatter<Char, ArgFormatter> &f, const Char *&format_str, const T &value);
 
 /**
   \rst
@@ -1842,24 +1840,6 @@ class ArgFormatterBase : public ArgVisitor<Impl, void> {
   }
 };
 
-// An argument formatter.
-template <typename Char>
-class BasicArgFormatter :
-    public ArgFormatterBase<BasicArgFormatter<Char>, Char> {
- private:
-  BasicFormatter<Char> &formatter_;
-  const Char *format_;
-
- public:
-  BasicArgFormatter(BasicFormatter<Char> &f, FormatSpec &s, const Char *fmt)
-  : ArgFormatterBase<BasicArgFormatter<Char>, Char>(f.writer(), s),
-    formatter_(f), format_(fmt) {}
-
-  void visit_custom(Arg::CustomValue c) {
-    c.format(&formatter_, c.value, &format_);
-  }
-};
-
 class FormatterBase {
  private:
   ArgList args_;
@@ -1927,6 +1907,32 @@ class PrintfFormatter : private FormatterBase {
 };
 }  // namespace internal
 
+// An argument formatter.
+template <typename Impl, typename Char>
+class BasicArgFormatter : public internal::ArgFormatterBase<Impl, Char> {
+ private:
+  BasicFormatter<Char, Impl> &formatter_;
+  const Char *format_;
+
+ public:
+  BasicArgFormatter(BasicFormatter<Char, Impl> &f,
+                    FormatSpec &s, const Char *fmt)
+  : internal::ArgFormatterBase<Impl, Char>(f.writer(), s),
+    formatter_(f), format_(fmt) {}
+
+  void visit_custom(internal::Arg::CustomValue c) {
+    c.format(&formatter_, c.value, &format_);
+  }
+};
+
+// The default argument formatter.
+template <typename Char>
+class ArgFormatter : public BasicArgFormatter<ArgFormatter<Char>, Char> {
+ public:
+  ArgFormatter(BasicFormatter<Char> &f, FormatSpec &s, const Char *fmt)
+  : BasicArgFormatter<ArgFormatter<Char>, Char>(f, s, fmt) {}
+};
+
 /** This template formats data and writes the output to a writer. */
 template <typename CharType, typename ArgFormatter>
 class BasicFormatter : private internal::FormatterBase {
@@ -3009,8 +3015,9 @@ typedef BasicArrayWriter<char> ArrayWriter;
 typedef BasicArrayWriter<wchar_t> WArrayWriter;
 
 // Formats a value.
-template <typename Char, typename T>
-void format(BasicFormatter<Char> &f, const Char *&format_str, const T &value) {
+template <typename Char, typename ArgFormatter, typename T>
+void format(BasicFormatter<Char, ArgFormatter> &f,
+            const Char *&format_str, const T &value) {
   internal::MemoryBuffer<Char, internal::INLINE_BUFFER_SIZE> buffer;
 
   internal::FormatBuf<Char> format_buf(buffer);
diff --git a/test/format-test.cc b/test/format-test.cc
index 121a7be6..b15c8aac 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1671,7 +1671,7 @@ TEST(FormatTest, EmptyCustomOutput) {
 }
 
 class MockArgFormatter :
-    public fmt::internal::ArgFormatterBase<MockArgFormatter, char>  {
+    public fmt::internal::ArgFormatterBase<MockArgFormatter, char> {
  public:
   typedef fmt::internal::ArgFormatterBase<MockArgFormatter, char> Base;
 
@@ -1694,3 +1694,19 @@ FMT_VARIADIC(void, custom_format, const char *)
 TEST(FormatTest, CustomArgFormatter) {
   custom_format("{}", 42);
 }
+
+struct TestArgFormatter : fmt::BasicArgFormatter<TestArgFormatter, char> {
+  TestArgFormatter(fmt::BasicFormatter<char, TestArgFormatter> &f,
+                   fmt::FormatSpec &s, const char *fmt)
+    : fmt::BasicArgFormatter<TestArgFormatter, char>(f, s, fmt) {}
+};
+
+TEST(ArgFormatterTest, CustomArg) {
+  fmt::MemoryWriter writer;
+  typedef fmt::BasicFormatter<char, TestArgFormatter> Formatter;
+  Formatter formatter(fmt::ArgList(), writer);
+  fmt::FormatSpec spec;
+  TestArgFormatter af(formatter, spec, "}");
+  af.visit(fmt::internal::MakeArg<Formatter>(TestEnum()));
+  EXPECT_EQ("TestEnum", writer.str());
+}