Add force_multiline_arrays formatting flag and corresponding tests. With this flag set, all arrays will be printed one element per line.

Author: rafal-c

include/toml++/impl/formatter.hpp

@@ -130,6 +130,12 @@ TOML_IMPL_NAMESPACE_START
 			return !!(config_.flags & format_flags::terse_key_value_pairs);
 		}
 
+		TOML_PURE_INLINE_GETTER
+		bool force_multiline_arrays() const noexcept
+		{
+			return !!(config_.flags & format_flags::force_multiline_arrays);
+		}
+
 		TOML_EXPORTED_MEMBER_FUNCTION
 		void attach(std::ostream& stream) noexcept;
 

include/toml++/impl/forward_declarations.hpp

@@ -343,6 +343,9 @@ TOML_NAMESPACE_START // abi namespace
 
 		/// \brief Avoids the use of whitespace around key-value pairs.
 		terse_key_value_pairs = (1ull << 12),
+
+		/// \brief Always print multiline arrays (one element per line).
+		force_multiline_arrays = (1ull << 13),
 	};
 	TOML_MAKE_FLAGS(format_flags);
 

include/toml++/impl/toml_formatter.inl

@@ -179,10 +179,11 @@ TOML_NAMESPACE_START
 		}
 
 		const auto original_indent = indent();
-		const auto multiline	   = TOML_ANON_NAMESPACE::toml_formatter_forces_multiline(
-			  arr,
-			  120u,
-			  indent_columns() * static_cast<size_t>(original_indent < 0 ? 0 : original_indent));
+		const auto multiline	   = force_multiline_arrays()
+							|| TOML_ANON_NAMESPACE::toml_formatter_forces_multiline(
+								   arr,
+								   120u,
+								   indent_columns() * static_cast<size_t>(original_indent < 0 ? 0 : original_indent));
 
 		print_unformatted("["sv);
 

tests/manipulating_tables.cpp

@@ -614,6 +614,94 @@ key8 = [
 ])"sv;
 		CHECK(to_string(input, toml_formatter::default_flags, format_flags::indentation)
 			  == expected_without_indentation);
+
+		// forcing multiline arrays: even short arrays become one-per-line (with array elements indented)
+		constexpr auto expected_forced_multiline = R"(key1 = 'val1'
+key2 = [
+    1,
+    2,
+    3,
+    4,
+    '5'
+]
+key3 = [
+    'this is a really long array',
+    'and should be split over multiple lines',
+    'by the formatter',
+    'unless i dun goofed',
+    'i guess thats what tests are for'
+]
+
+[sub1]
+key4 = 'val'
+
+[sub2]
+key5 = 'val'
+
+    [sub2.sub3]
+    key6 = 'val'
+    key7 = [
+        1,
+        2,
+        3,
+        4,
+        '5'
+    ]
+    key8 = [
+        'this is a really long array',
+        'and should be split over multiple lines',
+        'by the formatter',
+        'unless i dun goofed',
+        'i guess thats what tests are for'
+    ])"sv;
+
+		CHECK(to_string(input, toml_formatter::default_flags | format_flags::force_multiline_arrays)
+			  == expected_forced_multiline);
+
+		// forcing multiline arrays without indenting array elements
+		constexpr auto expected_forced_without_indented_arrays = R"(key1 = 'val1'
+key2 = [
+1,
+2,
+3,
+4,
+'5'
+]
+key3 = [
+'this is a really long array',
+'and should be split over multiple lines',
+'by the formatter',
+'unless i dun goofed',
+'i guess thats what tests are for'
+]
+
+[sub1]
+key4 = 'val'
+
+[sub2]
+key5 = 'val'
+
+    [sub2.sub3]
+    key6 = 'val'
+    key7 = [
+    1,
+    2,
+    3,
+    4,
+    '5'
+    ]
+    key8 = [
+    'this is a really long array',
+    'and should be split over multiple lines',
+    'by the formatter',
+    'unless i dun goofed',
+    'i guess thats what tests are for'
+    ])"sv;
+
+		CHECK(to_string(input,
+						toml_formatter::default_flags | format_flags::force_multiline_arrays,
+						format_flags::indent_array_elements)
+			  == expected_forced_without_indented_arrays);
 	}
 }