Added formatter for exceptions.

source/mijin/util/exception.hpp

@@ -4,8 +4,11 @@
 #ifndef MIJIN_UTIL_EXCEPTION_HPP_INCLUDED
 #define MIJIN_UTIL_EXCEPTION_HPP_INCLUDED 1
 
+#include <format>
 #include <stdexcept>
+#include <typeinfo>
 
+#include "../detect.hpp"
 #include "../debug/stacktrace.hpp"
 
 namespace mijin
@@ -73,5 +76,76 @@ void walkExceptionCause(const std::exception_ptr& cause, TFunc func)
         }
     }
 }
+
+template<typename TFunc>
+void walkException(const std::exception& exc, TFunc func)
+{
+    func(exc);
+}
+
+template<typename TFunc>
+void walkException(const mijin::Exception& exc, TFunc func)
+{
+    func(exc);
+    walkExceptionCause(exc.getCause(), func);
+}
 } // namespace mijin
+
+template<typename TChar>
+struct std::formatter<mijin::Exception, TChar>
+{
+    using char_t = TChar;
+
+    template<class TContext>
+    constexpr TContext::iterator parse(TContext& ctx)
+    {
+        auto it = ctx.begin();
+        auto end = ctx.end();
+
+        if (it != end && *it != MIJIN_SMART_QUOTE(char_t, '}'))
+        {
+            throw std::format_error("invalid format");
+        }
+
+        return it;
+    }
+
+    template<typename TContext>
+    TContext::iterator format(const mijin::Exception& exception, TContext& ctx) const
+    {
+        using namespace std::literals;
+
+        auto it = ctx.out();
+        bool first = true;
+        mijin::walkException(exception, [&]<typename T>(const T& exc)
+        {
+            if constexpr (!std::is_same_v<T, std::nullptr_t>)
+            {
+                if (!first) {
+                    it = std::ranges::copy(MIJIN_SMART_QUOTE(char_t, "\nCaused by:\n"sv), it).out;
+                }
+                first = false;
+#if MIJIN_RTTI
+                it = std::ranges::copy(std::basic_string_view(typeid(exc).name()), it).out;
+                it = std::ranges::copy(MIJIN_SMART_QUOTE(char_t, ": "sv), it).out;
+#endif
+                it = std::ranges::copy(std::basic_string_view(exc.what()), it).out;
+                if constexpr (std::is_same_v<T, mijin::Exception>)
+                {
+                    if (const mijin::Result<mijin::Stacktrace>& trace = exc.getStacktrace(); trace.isSuccess())
+                    {
+                        *it = MIJIN_SMART_QUOTE(char_t, '\n');
+                        ++it;
+                        it = std::format_to(it, MIJIN_SMART_QUOTE(char_t, "{}"), trace.getValue());
+                    }
+                }
+            }
+            else
+            {
+                it = std::ranges::copy(MIJIN_SMART_QUOTE(char_t, "<unknown exception>"sv), it).out;
+            }
+        });
+        return it;
+    }
+};
 #endif // MIJIN_UTIL_EXCEPTION_HPP_INCLUDED