Fix enum formatting

This attempt removes the enums from fmt altogether, fmt never sees an enum,
only ints.

2 files changed, 78 insertions, 4 deletions

diff --git a/xbmc/utils/StringUtils.h b/xbmc/utils/StringUtils.h
index e6dca5a04d..1abc071cc5 100644
--- a/xbmc/utils/StringUtils.h
+++ b/xbmc/utils/StringUtils.h
@@ -51,6 +51,25 @@ DEF_TO_STR_VALUE(foo) // outputs "4"
 #define DEF_TO_STR_NAME(x) #x
 #define DEF_TO_STR_VALUE(x) DEF_TO_STR_NAME(x)
 
+template< bool B, class T = void >
+using enable_if_t = typename std::enable_if<B,T>::type;
+
+template< class T > struct remove_rvalue_reference      {typedef T type;};
+template< class T > struct remove_rvalue_reference<T&>  {typedef T& type;};
+template< class T > struct remove_rvalue_reference<T*>  {typedef T* type;};
+template< class T > struct remove_rvalue_reference<T&&> {typedef T type;};
+
+template<typename T, enable_if_t<!std::is_enum<T>::value, int> = 0>
+constexpr auto EnumToInt(T&& arg) noexcept -> typename remove_rvalue_reference<decltype(arg)>::type
+{
+  return arg;
+}
+template<typename T, enable_if_t<std::is_enum<T>::value, int> = 0>
+constexpr auto EnumToInt(T&& arg) noexcept -> int
+{
+  return static_cast<int>(arg);
+}
+
 class StringUtils
 {
 public:
@@ -69,9 +88,9 @@ public:
   static std::string Format(const std::string& fmt, Args&&... args)
   {
     // coverity[fun_call_w_exception : FALSE]
-    auto result = ::fmt::format(fmt, std::forward<Args>(args)...);
+    auto result = ::fmt::format(fmt, EnumToInt(std::forward<Args>(args))...);
     if (result == fmt)
-      result = ::fmt::sprintf(fmt, std::forward<Args>(args)...);
+      result = ::fmt::sprintf(fmt, EnumToInt(std::forward<Args>(args))...);
 
     return result;
   }
@@ -79,9 +98,9 @@ public:
   static std::wstring Format(const std::wstring& fmt, Args&&... args)
   {
     // coverity[fun_call_w_exception : FALSE]
-    auto result = ::fmt::format(fmt, std::forward<Args>(args)...);
+    auto result = ::fmt::format(fmt, EnumToInt(std::forward<Args>(args))...);
     if (result == fmt)
-      result = ::fmt::sprintf(fmt, std::forward<Args>(args)...);
+      result = ::fmt::sprintf(fmt, EnumToInt(std::forward<Args>(args))...);
 
     return result;
   }
diff --git a/xbmc/utils/test/TestStringUtils.cpp b/xbmc/utils/test/TestStringUtils.cpp
index baf1d42783..a25a45a246 100644
--- a/xbmc/utils/test/TestStringUtils.cpp
+++ b/xbmc/utils/test/TestStringUtils.cpp
@@ -11,6 +11,32 @@
 
 #include "gtest/gtest.h"
 
+enum class ECG
+{
+  A,
+  B
+};
+
+enum EG
+{
+  C,
+  D
+};
+
+namespace test_enum
+{
+enum class ECN
+{
+  A = 1,
+  B
+};
+enum EN
+{
+  C = 1,
+  D
+};
+}
+
 TEST(TestStringUtils, Format)
 {
   std::string refstr = "test 25 2.7 ff FF";
@@ -22,6 +48,35 @@ TEST(TestStringUtils, Format)
   EXPECT_STREQ("", varstr.c_str());
 }
 
+TEST(TestStringUtils, FormatEnum)
+{
+  const char* zero = "0";
+  const char* one = "1";
+
+  std::string varstr = StringUtils::Format("{}", ECG::A);
+  EXPECT_STREQ(zero, varstr.c_str());
+
+  varstr = StringUtils::Format("{}", EG::C);
+  EXPECT_STREQ(zero, varstr.c_str());
+
+  varstr = StringUtils::Format("{}", test_enum::ECN::A);
+  EXPECT_STREQ(one, varstr.c_str());
+
+  varstr = StringUtils::Format("{}", test_enum::EN::C);
+  EXPECT_STREQ(one, varstr.c_str());
+}
+
+TEST(TestStringUtils, FormatEnumWidth)
+{
+  const char* one = "01";
+
+  std::string varstr = StringUtils::Format("{:02d}", ECG::B);
+  EXPECT_STREQ(one, varstr.c_str());
+
+  varstr = StringUtils::Format("%02d", EG::D);
+  EXPECT_STREQ(one, varstr.c_str());
+}
+
 TEST(TestStringUtils, ToUpper)
 {
   std::string refstr = "TEST";