added formatter indentation flags (closes #120)

also:
- minor refactoring (esp. GNU attributes)
- added documentation about formatters being free to ignore flags where necessary

.clang-format

@@ -156,12 +156,16 @@ StatementMacros:
   - TOML_ALWAYS_INLINE
   - TOML_API
   - TOML_ATTR
+  - TOML_CONST_GETTER
+  - TOML_CONST_INLINE_GETTER
   - TOML_EXTERNAL_LINKAGE
   - TOML_INTERNAL_LINKAGE
   - TOML_MEMBER_ATTR
   - TOML_NEVER_INLINE
   - TOML_NODISCARD
   - TOML_NODISCARD_CTOR
+  - TOML_PURE_GETTER
+  - TOML_PURE_INLINE_GETTER
   - TOML_RETURNS_BY_THROWING
 TabWidth:        4
 TypenameMacros:

cpp.hint

@@ -1,24 +1,28 @@
+#define TOML_ABI_NAMESPACE_BOOL(...)			static_assert(true)
+#define TOML_ABI_NAMESPACE_END					static_assert(true)
+#define TOML_ABSTRACT_BASE
+#define TOML_ALWAYS_INLINE						inline
+#define TOML_ANON_NAMESPACE_END					static_assert(true)
+#define TOML_ANON_NAMESPACE_START				namespace
 #define TOML_API
 #define TOML_ATTR(...)
-#define TOML_ALWAYS_INLINE						inline
-#define TOML_NEVER_INLINE
-#define TOML_TRIVIAL_ABI
-#define TOML_ABSTRACT_BASE
-#define TOML_EMPTY_BASES
+#define TOML_CONST_GETTER
+#define TOML_CONST_INLINE_GETTER				inline
 #define TOML_CONSTRAINED_TEMPLATE(cond, ...)	template <__VA_ARGS__>
-#define TOML_LIKELY(...)						(__VA_ARGS__)
-#define TOML_UNLIKELY(...)						(__VA_ARGS__)
-#define TOML_NODISCARD
-#define TOML_NODISCARD_CTOR
-#define TOML_RETURNS_BY_THROWING
+#define TOML_EMPTY_BASES
 #define TOML_EXTERN_NOEXCEPT(...)
 #define TOML_EXTERNAL_LINKAGE
+#define TOML_IMPL_NAMESPACE_END					static_assert(true)
+#define TOML_IMPL_NAMESPACE_START				namespace toml::impl
 #define TOML_INTERNAL_LINKAGE					static
-#define TOML_ANON_NAMESPACE_START				namespace
-#define TOML_ANON_NAMESPACE_END					static_assert(true)
-#define TOML_ABI_NAMESPACE_BOOL(...)			static_assert(true)
-#define TOML_ABI_NAMESPACE_END					static_assert(true)
-#define TOML_NAMESPACE_START					namespace toml
+#define TOML_LIKELY(...)						(__VA_ARGS__)
 #define TOML_NAMESPACE_END						static_assert(true)
-#define TOML_IMPL_NAMESPACE_START				namespace toml::impl
-#define TOML_IMPL_NAMESPACE_END					static_assert(true)
+#define TOML_NAMESPACE_START					namespace toml
+#define TOML_NEVER_INLINE
+#define TOML_NODISCARD
+#define TOML_NODISCARD_CTOR
+#define TOML_PURE_GETTER
+#define TOML_PURE_INLINE_GETTER					inline
+#define TOML_RETURNS_BY_THROWING
+#define TOML_TRIVIAL_ABI
+#define TOML_UNLIKELY(...)						(__VA_ARGS__)

include/toml++/impl/default_formatter.h

@@ -81,21 +81,25 @@ TOML_NAMESPACE_START
 		TOML_API
 		void print();
 
+		static constexpr format_flags mandatory_flags = format_flags::none;
+		static constexpr format_flags ignored_flags	  = format_flags::none;
+
 		/// \endcond
 
 	  public:
 		/// \brief	The default flags for a default_formatter.
-		static constexpr format_flags default_flags = format_flags::allow_literal_strings
-													| format_flags::allow_multi_line_strings
-													| format_flags::allow_value_format_flags;
+		static constexpr format_flags default_flags = format_flags::allow_literal_strings	 //
+													| format_flags::allow_multi_line_strings //
+													| format_flags::allow_value_format_flags //
+													| format_flags::indentation;
 
 		/// \brief	Constructs a default formatter and binds it to a TOML object.
 		///
 		/// \param 	source	The source TOML object.
 		/// \param 	flags 	Format option flags.
 		TOML_NODISCARD_CTOR
 		explicit default_formatter(const toml::node& source, format_flags flags = default_flags) noexcept
-			: base{ source, flags }
+			: base{ source, (flags | mandatory_flags) & ~ignored_flags }
 		{}
 
 #if defined(DOXYGEN) || (TOML_PARSER && !TOML_EXCEPTIONS)
@@ -124,7 +128,7 @@ TOML_NAMESPACE_START
 		/// \param 	flags 	Format option flags.
 		TOML_NODISCARD_CTOR
 		explicit default_formatter(const toml::parse_result& result, format_flags flags = default_flags) noexcept
-			: base{ result, flags }
+			: base{ result, (flags | mandatory_flags) & ~ignored_flags }
 		{}
 
 #endif

include/toml++/impl/default_formatter.inl

@@ -260,7 +260,8 @@ TOML_NAMESPACE_START
 			{
 				if (original_indent < 0)
 					base::indent(0);
-				base::increase_indent();
+				if (base::indent_array_elements())
+					base::increase_indent();
 			}
 			else
 				impl::print_to_stream(base::stream(), ' ');
@@ -380,7 +381,8 @@ TOML_NAMESPACE_START
 			if (!skip_self)
 			{
 				print_pending_table_separator();
-				base::increase_indent();
+				if (base::indent_sub_tables())
+					base::increase_indent();
 				base::print_indent();
 				impl::print_to_stream(base::stream(), "["sv);
 				print_key_path();
@@ -391,7 +393,7 @@ TOML_NAMESPACE_START
 			print(child_tbl);
 
 			key_path_.pop_back();
-			if (!skip_self)
+			if (!skip_self && base::indent_sub_tables())
 				base::decrease_indent();
 		}
 
@@ -402,7 +404,8 @@ TOML_NAMESPACE_START
 				continue;
 			auto& arr = *reinterpret_cast<const array*>(&v);
 
-			base::increase_indent();
+			if (base::indent_sub_tables())
+				base::increase_indent();
 			key_path_.push_back(make_key_segment(k));
 
 			for (size_t i = 0; i < arr.size(); i++)
@@ -417,7 +420,8 @@ TOML_NAMESPACE_START
 			}
 
 			key_path_.pop_back();
-			base::decrease_indent();
+			if (base::indent_sub_tables())
+				base::decrease_indent();
 		}
 	}
 

include/toml++/impl/formatter.h

@@ -16,32 +16,30 @@ TOML_IMPL_NAMESPACE_START
 	  private:
 		const toml::node* source_;
 		std::ostream* stream_ = {};
-		format_flags flags_;
-		int indent_;
-		bool naked_newline_;
+		format_flags flags_; //
+		int indent_;		 // these are set in attach()
+		bool naked_newline_; //
 #if TOML_PARSER && !TOML_EXCEPTIONS
 		const parse_result* result_ = {};
 #endif
 
 	  protected:
-		TOML_NODISCARD
-		TOML_ALWAYS_INLINE
+		static constexpr size_t indent_columns			= 4;
+		static constexpr std::string_view indent_string = "    "sv;
+
+		TOML_PURE_INLINE_GETTER
 		const toml::node& source() const noexcept
 		{
 			return *source_;
 		}
 
-		TOML_NODISCARD
-		TOML_ALWAYS_INLINE
+		TOML_PURE_INLINE_GETTER
 		std::ostream& stream() const noexcept
 		{
 			return *stream_;
 		}
 
-		static constexpr size_t indent_columns			= 4;
-		static constexpr std::string_view indent_string = "    "sv;
-
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
 		int indent() const noexcept
 		{
 			return indent_;
@@ -62,31 +60,43 @@ TOML_IMPL_NAMESPACE_START
 			indent_--;
 		}
 
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
+		bool indent_array_elements() const noexcept
+		{
+			return !!(flags_ & format_flags::indent_array_elements);
+		}
+
+		TOML_PURE_INLINE_GETTER
+		bool indent_sub_tables() const noexcept
+		{
+			return !!(flags_ & format_flags::indent_sub_tables);
+		}
+
+		TOML_PURE_INLINE_GETTER
 		bool quote_dates_and_times() const noexcept
 		{
 			return !!(flags_ & format_flags::quote_dates_and_times);
 		}
 
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
 		bool literal_strings_allowed() const noexcept
 		{
 			return !!(flags_ & format_flags::allow_literal_strings);
 		}
 
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
 		bool multi_line_strings_allowed() const noexcept
 		{
 			return !!(flags_ & format_flags::allow_multi_line_strings);
 		}
 
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
 		bool value_format_flags_allowed() const noexcept
 		{
 			return !!(flags_ & format_flags::allow_value_format_flags);
 		}
 
-		TOML_NODISCARD
+		TOML_PURE_INLINE_GETTER
 		bool naked_newline() const noexcept
 		{
 			return naked_newline_;

include/toml++/impl/formatter.inl

@@ -213,18 +213,29 @@ TOML_IMPL_NAMESPACE_START
 		}
 	}
 
+#if TOML_PARSER && !TOML_EXCEPTIONS
+
 	TOML_EXTERNAL_LINKAGE
-	bool formatter::dump_failed_parse_result() noexcept(!TOML_PARSER || TOML_EXCEPTIONS)
+	bool formatter::dump_failed_parse_result() noexcept(false)
 	{
-#if TOML_PARSER && !TOML_EXCEPTIONS
 		if (result_ && !(*result_))
 		{
 			stream() << result_->error();
 			return true;
 		}
-#endif
 		return false;
 	}
+
+#else
+
+	TOML_EXTERNAL_LINKAGE
+	TOML_ATTR(const)
+	bool formatter::dump_failed_parse_result() noexcept(true)
+	{
+		return false;
+	}
+
+#endif
 }
 TOML_IMPL_NAMESPACE_END;
 

include/toml++/impl/forward_declarations.h

@@ -267,7 +267,7 @@ TOML_NAMESPACE_START // abi namespace
 	}
 
 	/// \brief Metadata associated with TOML values.
-	enum class value_flags : uint8_t
+	enum class value_flags : uint16_t
 	{
 		/// \brief None.
 		none,
@@ -284,7 +284,10 @@ TOML_NAMESPACE_START // abi namespace
 	TOML_MAKE_FLAGS(value_flags);
 
 	/// \brief	Format flags for modifying how TOML data is printed to streams.
-	enum class format_flags : uint8_t
+	///
+	/// \note	Formatters may disregard/override any of these flags according to the requirements of their
+	///			output target (e.g. #toml::json_formatter JSON always apply quotes to dates and times).
+	enum class format_flags : uint64_t
 	{
 		/// \brief None.
 		none,
@@ -300,6 +303,15 @@ TOML_NAMESPACE_START // abi namespace
 
 		/// \brief Values with special format flags will be formatted accordingly.
 		allow_value_format_flags = 8,
+
+		/// \brief Apply indentation to tables nested within other tables/arrays.
+		indent_sub_tables = 16,
+
+		/// \brief Apply indentation to array elements when the array is forced to wrap over multiple lines.
+		indent_array_elements = 32,
+
+		/// \brief Combination mask of all indentation-enabling flags.
+		indentation = indent_sub_tables | indent_array_elements,
 	};
 	TOML_MAKE_FLAGS(format_flags);
 

include/toml++/impl/json_formatter.h

@@ -55,19 +55,24 @@ TOML_NAMESPACE_START
 		TOML_API
 		void print();
 
+		static constexpr format_flags mandatory_flags = format_flags::quote_dates_and_times;
+		static constexpr format_flags ignored_flags =
+			format_flags::allow_literal_strings | format_flags::allow_multi_line_strings;
+
 		/// \endcond
 
 	  public:
 		/// \brief	The default flags for a json_formatter.
-		static constexpr format_flags default_flags = format_flags::quote_dates_and_times;
+		static constexpr format_flags default_flags = format_flags::quote_dates_and_times //
+													| format_flags::indentation;
 
 		/// \brief	Constructs a JSON formatter and binds it to a TOML object.
 		///
 		/// \param 	source	The source TOML object.
 		/// \param 	flags 	Format option flags.
 		TOML_NODISCARD_CTOR
 		explicit json_formatter(const toml::node& source, format_flags flags = default_flags) noexcept
-			: base{ source, flags }
+			: base{ source, (flags | mandatory_flags) & ~ignored_flags }
 		{}
 
 #if defined(DOXYGEN) || (TOML_PARSER && !TOML_EXCEPTIONS)
@@ -98,7 +103,7 @@ TOML_NAMESPACE_START
 		/// \param 	flags 	Format option flags.
 		TOML_NODISCARD_CTOR
 		explicit json_formatter(const toml::parse_result& result, format_flags flags = default_flags) noexcept
-			: base{ result, flags }
+			: base{ result, (flags | mandatory_flags) & ~ignored_flags }
 		{}
 
 #endif

include/toml++/impl/json_formatter.inl

@@ -27,7 +27,8 @@ TOML_NAMESPACE_START
 		else
 		{
 			impl::print_to_stream(base::stream(), '{');
-			base::increase_indent();
+			if (base::indent_sub_tables())
+				base::increase_indent();
 			bool first = false;
 			for (auto&& [k, v] : tbl)
 			{
@@ -49,7 +50,8 @@ TOML_NAMESPACE_START
 					default: base::print_value(v, type);
 				}
 			}
-			base::decrease_indent();
+			if (base::indent_sub_tables())
+				base::decrease_indent();
 			base::print_newline(true);
 			base::print_indent();
 			impl::print_to_stream(base::stream(), '}');
@@ -65,7 +67,8 @@ TOML_NAMESPACE_START
 		else
 		{
 			impl::print_to_stream(base::stream(), '[');
-			base::increase_indent();
+			if (base::indent_array_elements())
+				base::increase_indent();
 			for (size_t i = 0; i < arr.size(); i++)
 			{
 				if (i > 0u)
@@ -83,7 +86,8 @@ TOML_NAMESPACE_START
 					default: base::print_value(v, type);
 				}
 			}
-			base::decrease_indent();
+			if (base::indent_array_elements())
+				base::decrease_indent();
 			base::print_newline(true);
 			base::print_indent();
 			impl::print_to_stream(base::stream(), ']');