Relevant code printing when error reporting

Makefile

@@ -14,6 +14,7 @@ Obj=                 \
 		errors.o         \
 		interpreter.o    \
 		lexer.o          \
+		lines.o          \
 		location.o       \
 		number.o         \
 		parser.o         \

src/errors.cc

@@ -125,36 +125,47 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 
 	error_heading(os, err.location, Error_Level::Error, short_description);
 
+	auto const loc = err.location;
 	visit(Overloaded {
-		[&os](errors::Unrecognized_Character const& err) {
+		[&](errors::Unrecognized_Character const& err) {
 			os << "I encountered character in the source code that was not supposed to be here.\n";
 			os << "  Character Unicode code: U+" << std::hex << err.invalid_character << '\n';
 			os << "  Character printed: '" << utf8::Print{err.invalid_character} << "'\n";
 			os << "\n";
+
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+
 			os << "Musique only accepts characters that are unicode letters or ascii numbers and punctuation\n";
 		},
 
-		[&os](errors::Failed_Numeric_Parsing const& err) {
+		[&](errors::Failed_Numeric_Parsing const& err) {
 			constexpr auto Max = std::numeric_limits<decltype(Number::num)>::max();
 			constexpr auto Min = std::numeric_limits<decltype(Number::num)>::min();
-			os << "I tried to parse numeric literal, but I failed.";
+			os << "I tried to parse numeric literal, but I failed.\n\n";
+
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+
 			if (err.reason == std::errc::result_out_of_range) {
-				os << " Declared number is outside of valid range of numbers that can be represented.\n";
+				os << "\nDeclared number is outside of valid range of numbers that can be represented.\n";
-				os << "  Only numbers in range [" << Min << ", " << Max << "] are supported\n";
+				os << "Only numbers in range [" << Min << ", " << Max << "] are supported\n";
 			}
 		},
 
-		[&os](errors::internal::Unexpected_Token const& ut) {
+		[&](errors::internal::Unexpected_Token const& ut) {
 			os << "I encountered unexpected token during " << ut.when << '\n';
 			os << "  Token type: " << ut.type << '\n';
-			os << "  Token source: " << ut.source << '\n';
+			os << "  Token source: " << ut.source << "\n\n";
+
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
 
 			os << pretty::begin_comment << "\nThis error is considered an internal one. It should not be displayed to the end user.\n" << pretty::end;
 			encourage_contact(os);
 		},
 
-		[&os](errors::Expected_Expression_Separator_Before const& err) {
+		[&](errors::Expected_Expression_Separator_Before const& err) {
-			os << "I failed to parse following code, due to missing semicolon before it!\n";
+			os << "I failed to parse following code, due to missing semicolon before it!\n\n";
+
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
 
 			if (err.what == "var") {
 				os << "\nIf you want to create variable inside expression try wrapping them inside parentheses like this:\n";
@@ -162,9 +173,10 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			}
 		},
 
-		[&os](errors::Literal_As_Identifier const& err) {
+		[&](errors::Literal_As_Identifier const& err) {
-			os << "I expected an identifier in " << err.context << ", but found" << (err.type_name.empty() ? "" : " ") << err.type_name << " value = '" << err.source << "'\n";
+			os << "I expected an identifier in " << err.context << ", but found" << (err.type_name.empty() ? "" : " ") << err.type_name << " value = '" << err.source << "'\n\n";
 
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
 
 			if (err.type_name == "chord") {
 				os << "\nTry renaming to different name or appending with something that is not part of chord literal like 'x'\n";
@@ -176,10 +188,10 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			}
 		},
 
-		[&os](errors::Not_Callable const&)                     { unimplemented(); },
+		[&](errors::Not_Callable const&)                     { unimplemented(); },
-		[&os](errors::Undefined_Operator const&)               { unimplemented(); },
+		[&](errors::Undefined_Operator const&)               { unimplemented(); },
-		[&os](errors::Unexpected_Keyword const&)               { unimplemented(); },
+		[&](errors::Unexpected_Keyword const&)               { unimplemented(); },
-		[&os](errors::Unexpected_Empty_Source const&)          { unimplemented(); }
+		[&](errors::Unexpected_Empty_Source const&)          { unimplemented(); }
 	}, err.details);
 
 	return os;

src/lines.cc

@@ -0,0 +1,36 @@
+#include <musique.hh>
+
+#include <iomanip>
+
+Lines Lines::the;
+
+void Lines::add_file(std::string filename, std::string_view source)
+{
+	auto file = lines.insert({ filename, {} });
+	auto &lines_in_file = file.first->second;
+
+	while (not source.empty()) {
+		auto end = source.find('\n');
+		if (end == std::string_view::npos) {
+			lines_in_file.push_back({ source.data(), end });
+			break;
+		} else {
+			lines_in_file.push_back({ source.data(), end });
+			source.remove_prefix(end+1);
+		}
+	}
+}
+
+void Lines::add_line(std::string const& filename, std::string_view source)
+{
+	lines[filename].push_back(source);
+}
+
+void Lines::print(std::ostream &os, std::string const& filename, unsigned first_line, unsigned last_line) const
+{
+	auto const& file = lines.at(filename);
+	for (auto i = first_line; i <= last_line; ++i) {
+		os << std::setw(3) << std::right << i << " | " << file[i-1] << '\n';
+	}
+	os << std::flush;
+}

src/main.cc

@@ -166,11 +166,13 @@ static Result<void> Main(std::span<char const*> args)
 
 	for (auto const& [is_file, argument] : runnables) {
 		if (!is_file) {
+			Lines::the.add_line("<arguments>", argument);
 			Try(runner.run(argument, "<arguments>"));
 			continue;
 		}
-		auto const path = argument;
+		auto path = argument;
 		if (path == "-") {
+			path = "<stdin>";
 			eternal_sources.emplace_back(std::istreambuf_iterator<char>(std::cin), std::istreambuf_iterator<char>());
 		} else {
 			if (not fs::exists(path)) {
@@ -181,6 +183,7 @@ static Result<void> Main(std::span<char const*> args)
 			eternal_sources.emplace_back(std::istreambuf_iterator<char>(source_file), std::istreambuf_iterator<char>());
 		}
 
+		Lines::the.add_file(std::string(path), eternal_sources.back());
 		Try(runner.run(eternal_sources.back(), path));
 	}
 
@@ -216,6 +219,7 @@ static Result<void> Main(std::span<char const*> args)
 				continue;
 			}
 
+			Lines::the.add_line("<repl>", raw);
 			auto result = runner.run(raw, "<repl>", true);
 			if (not result.has_value()) {
 				std::cout << std::flush;

src/musique.hh

@@ -392,6 +392,23 @@ std::ostream& operator<<(std::ostream& os, Token const& tok);
 /// Token type debug printing
 std::ostream& operator<<(std::ostream& os, Token::Type type);
 
+struct Lines
+{
+	static Lines the;
+
+	/// Region of lines in files
+	std::unordered_map<std::string, std::vector<std::string_view>> lines;
+
+	/// Add lines from file
+	void add_file(std::string filename, std::string_view source);
+
+	/// Add single line into file (REPL usage)
+	void add_line(std::string const& filename, std::string_view source);
+
+	/// Print selected region
+	void print(std::ostream& os, std::string const& file, unsigned first_line, unsigned last_line) const;
+};
+
 /// Explicit marker of the end of file
 struct End_Of_File {};