Report nice error when without MIDI connection

include/musique.hh

@@ -112,6 +112,16 @@ namespace errors
 		std::string name;
 	};
 
+	/// When user tries to invoke some MIDI action but haven't established MIDI connection
+	struct Operation_Requires_Midi_Connection
+	{
+		/// If its input or output connection missing
+		bool is_input;
+
+		/// Name of the operation that was beeing invoked
+		std::string name;
+	};
+
 	/// Collection of messages that are considered internal and should not be printed to the end user.
 	namespace internal
 	{
@@ -136,6 +146,7 @@ namespace errors
 		Literal_As_Identifier,
 		Missing_Variable,
 		Not_Callable,
+		Operation_Requires_Midi_Connection,
 		Undefined_Operator,
 		Unexpected_Empty_Source,
 		Unexpected_Keyword,
@@ -952,7 +963,7 @@ struct Interpreter
 	void leave_scope();
 
 	/// Play note resolving any missing parameters with context via `midi_connection` member.
-	void play(Chord);
+	Result<void> play(Chord);
 
 	/// Add to global interpreter scope all builtin function definitions
 	///

include/musique_internal.hh

@@ -1,6 +1,8 @@
 #ifndef Musique_Internal_HH
 #define Musique_Internal_HH
 
+#include <musique.hh>
+
 /// Binary operation may be vectorized when there are two argument which one is indexable and other is not
 static inline bool may_be_vectorized(std::vector<Value> const& args)
 {
@@ -60,4 +62,7 @@ struct Interpreter::Incoming_Midi_Callbacks
 	}
 };
 
+enum class Midi_Connection_Type { Output, Input };
+Result<void> ensure_midi_connection_available(Interpreter&, Midi_Connection_Type, std::string_view operation_name);
+
 #endif

lib/midi

@@ -1 +1 @@
-Subproject commit ed5d959e60fd021ae4e545e0b39fe90cd1ec35a1
+Subproject commit f42b663f0d08fc629c7deb26cd32ee06fba76d83

src/builtin_functions.cc

@@ -5,7 +5,6 @@
 #include <memory>
 #include <iostream>
 
-
 void Interpreter::register_callbacks()
 {
 	assert(callbacks == nullptr, "This field should be uninitialized");
@@ -80,7 +79,7 @@ static inline Result<void> play_notes(Interpreter &interpreter, T args)
 			break;
 
 		case Value::Type::Music:
-			interpreter.play(arg.chord);
+			Try(interpreter.play(arg.chord));
 			break;
 
 		default:
@@ -294,9 +293,11 @@ error:
 	global.force_define("oct", &ctx_read_write_property<&Context::octave>);
 
 	global.force_define("par", +[](Interpreter &i, std::vector<Value> args) -> Result<Value> {
+		Try(ensure_midi_connection_available(i, Midi_Connection_Type::Output, "par"));
+
 		assert(args.size() >= 1, "par only makes sense for at least one argument"); // TODO(assert)
 		if (args.size() == 1) {
-			i.play(std::move(args.front()).chord);
+			Try(i.play(std::move(args.front()).chord));
 			return Value{};
 		}
 
@@ -309,7 +310,7 @@ error:
 		}
 
 		for (auto it = std::next(args.begin()); it != args.end(); ++it) {
-			i.play(std::move(*it).chord);
+			Try(i.play(std::move(*it).chord));
 		}
 
 		for (auto const& note : chord.notes) {

src/errors.cc

@@ -134,6 +134,7 @@ void unreachable(Location loc)
 std::ostream& operator<<(std::ostream& os, Error const& err)
 {
 	std::string_view short_description = visit(Overloaded {
+		[](errors::Operation_Requires_Midi_Connection const&)   { return "Operation requires MIDI connection"; },
 		[](errors::Missing_Variable const&)                     { return "Cannot find variable"; },
 		[](errors::Failed_Numeric_Parsing const&)               { return "Failed to parse a number"; },
 		[](errors::Not_Callable const&)                         { return "Value not callable"; },
@@ -154,13 +155,29 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 	error_heading(os, err.location, Error_Level::Error, short_description);
 
 	auto const loc = err.location;
+	auto const print_error_line = [&] {
+		if (loc->filename != "") {
+			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+		}
+	};
+
 	visit(Overloaded {
+		[&](errors::Operation_Requires_Midi_Connection const& err) {
+			os << "I cannot '" << err.name << "' due to lack of MIDI " << (err.is_input ? "input" : "output") << "connection\n";
+			os << "\n";
+
+			print_error_line();
+
+			os << "You can connect to given MIDI device by specifing port when running musique command like:\n";
+			os << (err.is_input ? "  --input" : "  --output") << " PORT\n";
+			os << "You can list all available ports with --list flag\n";
+		},
 		[&](errors::Missing_Variable const& err) {
 			os << "I encountered '" << err.name << "' that looks like variable but\n";
 			os << "I can't find it in surrounding scope or in one of parent's scopes\n";
 			os << "\n";
 
-			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+			print_error_line();
 
 			os << "\n";
 			os << "Variables can only be references in scope (block) where they been created\n";
@@ -172,7 +189,7 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			os << "  Character printed: '" << utf8::Print{err.invalid_character} << "'\n";
 			os << "\n";
 
-			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+			print_error_line();
 
 			os << "Musique only accepts characters that are unicode letters or ascii numbers and punctuation\n";
 		},
@@ -182,7 +199,7 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			constexpr auto Min = std::numeric_limits<decltype(Number::num)>::min();
 			os << "I tried to parse numeric literal, but I failed.\n\n";
 
-			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+			print_error_line();
 
 			if (err.reason == std::errc::result_out_of_range) {
 				os << "\nDeclared number is outside of valid range of numbers that can be represented.\n";
@@ -195,7 +212,7 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			os << "  Token type: " << ut.type << '\n';
 			os << "  Token source: " << ut.source << "\n\n";
 
-			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+			print_error_line();
 
 			os << pretty::begin_comment << "\nThis error is considered an internal one. It should not be displayed to the end user.\n";
 			os << "\n";
@@ -206,7 +223,7 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 		[&](errors::Expected_Expression_Separator_Before const& err) {
 			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);
+			print_error_line();
 
 			if (err.what == "var") {
 				os << "\nIf you want to create variable inside expression try wrapping them inside parentheses like this:\n";
@@ -217,7 +234,7 @@ std::ostream& operator<<(std::ostream& os, Error 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\n";
 
-			Lines::the.print(os, std::string(loc->filename), loc->line, loc->line);
+			print_error_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";

src/interpreter.cc

@@ -202,9 +202,9 @@ void Interpreter::leave_scope()
 	env = env->leave();
 }
 
-void Interpreter::play(Chord chord)
+Result<void> Interpreter::play(Chord chord)
 {
-	assert(midi_connection, "To play midi Interpreter requires instance of MIDI connection");
+	Try(ensure_midi_connection_available(*this, Midi_Connection_Type::Output, "play"));
 
 	auto &ctx = context_stack.back();
 
@@ -229,4 +229,37 @@ void Interpreter::play(Chord chord)
 		}
 		midi_connection->send_note_off(0, *note.into_midi_note(), 127);
 	}
+
+	return {};
+}
+
+Result<void> ensure_midi_connection_available(Interpreter &i, Midi_Connection_Type m, std::string_view operation_name)
+{
+	switch (m) {
+	break; case Midi_Connection_Type::Output:
+		if (i.midi_connection == nullptr || !i.midi_connection->supports_output()) {
+			return Error {
+				.details = errors::Operation_Requires_Midi_Connection {
+					.is_input = false,
+					.name = std::string(operation_name),
+				},
+				.location = {}
+			};
+		}
+
+	break; case Midi_Connection_Type::Input:
+		if (i.midi_connection == nullptr || !i.midi_connection->supports_input()) {
+			return Error {
+				.details = errors::Operation_Requires_Midi_Connection {
+					.is_input = false,
+					.name = std::string(operation_name),
+				},
+				.location = {}
+			};
+		}
+	break; default:
+		unreachable();
+	}
+
+	return {};
 }