Shell: Make <return> go to a new line when the command is incomplete

"incomplete" meaning that it has a syntax error that can be recovered
from by continuing the input.

Shell/AST.cpp

@@ -2481,6 +2481,10 @@ StringPartCompose::~StringPartCompose()
 void SyntaxError::dump(int level) const
 {
     Node::dump(level);
+    print_indented("(Error text)", level + 1);
+    print_indented(m_syntax_error_text, level + 2);
+    print_indented("(Can be recovered from)", level + 1);
+    print_indented(String::formatted("{}", m_is_continuable), level + 2);
 }
 
 RefPtr<Value> SyntaxError::run(RefPtr<Shell>)
@@ -2494,9 +2498,10 @@ void SyntaxError::highlight_in_editor(Line::Editor& editor, Shell&, HighlightMet
     editor.stylize({ m_position.start_offset, m_position.end_offset }, { Line::Style::Foreground(Line::Style::XtermColor::Red), Line::Style::Bold });
 }
 
-SyntaxError::SyntaxError(Position position, String error)
+SyntaxError::SyntaxError(Position position, String error, bool is_continuable)
     : Node(move(position))
     , m_syntax_error_text(move(error))
+    , m_is_continuable(is_continuable)
 {
     m_is_syntax_error = true;
 }

Shell/AST.h

@@ -418,8 +418,10 @@ public:
     const Position& position() const { return m_position; }
     void set_is_syntax_error(const SyntaxError& error_node)
     {
-        m_is_syntax_error = true;
-        m_syntax_error_node = error_node;
+        if (!m_is_syntax_error) {
+            m_is_syntax_error = true;
+            m_syntax_error_node = error_node;
+        }
     }
     virtual const SyntaxError& syntax_error_node() const
     {
@@ -1174,11 +1176,12 @@ private:
 
 class SyntaxError final : public Node {
 public:
-    SyntaxError(Position, String);
+    SyntaxError(Position, String, bool is_continuable = false);
     virtual ~SyntaxError();
     virtual void visit(NodeVisitor& visitor) override { visitor.visit(this); }
 
     const String& error_text() const { return m_syntax_error_text; }
+    bool is_continuable() const { return m_is_continuable; }
 
 private:
     NODE(SyntaxError);
@@ -1190,6 +1193,7 @@ private:
     virtual const SyntaxError& syntax_error_node() const override;
 
     String m_syntax_error_text;
+    bool m_is_continuable { false };
 };
 
 class Tilde final : public Node {

Shell/Parser.cpp

@@ -150,7 +150,7 @@ RefPtr<AST::Node> Parser::parse()
         auto syntax_error_node = create<AST::SyntaxError>("Unexpected tokens past the end");
         if (!toplevel)
             toplevel = move(syntax_error_node);
-        else
+        else if (!toplevel->is_syntax_error())
             toplevel->set_is_syntax_error(*syntax_error_node);
     }
 
@@ -276,7 +276,7 @@ RefPtr<AST::Node> Parser::parse_variable_decls()
             if (!command)
                 restore_to(*start);
             else if (!expect(')'))
-                command->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating close paren"));
+                command->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating close paren", true));
             expression = command;
         }
     }
@@ -350,7 +350,7 @@ RefPtr<AST::Node> Parser::parse_function_decl()
         RefPtr<AST::Node> syntax_error;
         {
             auto obrace_error_start = push_start();
-            syntax_error = create<AST::SyntaxError>("Expected an open brace '{' to start a function body");
+            syntax_error = create<AST::SyntaxError>("Expected an open brace '{' to start a function body", true);
         }
         if (!expect('{')) {
             return create<AST::FunctionDeclaration>(
@@ -368,7 +368,7 @@ RefPtr<AST::Node> Parser::parse_function_decl()
         RefPtr<AST::SyntaxError> syntax_error;
         {
             auto cbrace_error_start = push_start();
-            syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a function body");
+            syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a function body", true);
         }
         if (!expect('}')) {
             if (body)
@@ -409,7 +409,7 @@ RefPtr<AST::Node> Parser::parse_or_logical_sequence()
 
     auto right_and_sequence = parse_and_logical_sequence();
     if (!right_and_sequence)
-        right_and_sequence = create<AST::SyntaxError>("Expected an expression after '||'");
+        right_and_sequence = create<AST::SyntaxError>("Expected an expression after '||'", true);
 
     return create<AST::Or>(
         and_sequence.release_nonnull(),
@@ -433,7 +433,7 @@ RefPtr<AST::Node> Parser::parse_and_logical_sequence()
 
     auto right_and_sequence = parse_and_logical_sequence();
     if (!right_and_sequence)
-        right_and_sequence = create<AST::SyntaxError>("Expected an expression after '&&'");
+        right_and_sequence = create<AST::SyntaxError>("Expected an expression after '&&'", true);
 
     return create<AST::And>(
         pipe_sequence.release_nonnull(),
@@ -533,7 +533,7 @@ RefPtr<AST::Node> Parser::parse_for_loop()
         consume_while(is_whitespace);
         auto in_error_start = push_start();
         if (!expect("in")) {
-            auto syntax_error = create<AST::SyntaxError>("Expected 'in' after a variable name in a 'for' loop");
+            auto syntax_error = create<AST::SyntaxError>("Expected 'in' after a variable name in a 'for' loop", true);
             return create<AST::ForLoop>(move(variable_name), move(syntax_error), nullptr); // ForLoop Var Iterated Block
         }
         in_start_position = AST::Position { in_error_start->offset, m_offset, in_error_start->line, line() };
@@ -545,7 +545,7 @@ RefPtr<AST::Node> Parser::parse_for_loop()
         auto iter_error_start = push_start();
         iterated_expression = parse_expression();
         if (!iterated_expression) {
-            auto syntax_error = create<AST::SyntaxError>("Expected an expression in 'for' loop");
+            auto syntax_error = create<AST::SyntaxError>("Expected an expression in 'for' loop", true);
             return create<AST::ForLoop>(move(variable_name), move(syntax_error), nullptr, move(in_start_position)); // ForLoop Var Iterated Block
         }
     }
@@ -554,7 +554,7 @@ RefPtr<AST::Node> Parser::parse_for_loop()
     {
         auto obrace_error_start = push_start();
         if (!expect('{')) {
-            auto syntax_error = create<AST::SyntaxError>("Expected an open brace '{' to start a 'for' loop body");
+            auto syntax_error = create<AST::SyntaxError>("Expected an open brace '{' to start a 'for' loop body", true);
             return create<AST::ForLoop>(move(variable_name), iterated_expression.release_nonnull(), move(syntax_error), move(in_start_position)); // ForLoop Var Iterated Block
         }
     }
@@ -565,7 +565,7 @@ RefPtr<AST::Node> Parser::parse_for_loop()
         auto cbrace_error_start = push_start();
         if (!expect('}')) {
             auto error_start = push_start();
-            auto syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a 'for' loop body");
+            auto syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a 'for' loop body", true);
             if (body)
                 body->set_is_syntax_error(*syntax_error);
             else
@@ -592,7 +592,7 @@ RefPtr<AST::Node> Parser::parse_if_expr()
         auto cond_error_start = push_start();
         condition = parse_or_logical_sequence();
         if (!condition)
-            condition = create<AST::SyntaxError>("Expected a logical sequence after 'if'");
+            condition = create<AST::SyntaxError>("Expected a logical sequence after 'if'", true);
     }
 
     auto parse_braced_toplevel = [&]() -> RefPtr<AST::Node> {
@@ -600,7 +600,7 @@ RefPtr<AST::Node> Parser::parse_if_expr()
         {
             auto obrace_error_start = push_start();
             if (!expect('{')) {
-                body = create<AST::SyntaxError>("Expected an open brace '{' to start an 'if' true branch");
+                body = create<AST::SyntaxError>("Expected an open brace '{' to start an 'if' true branch", true);
             }
         }
 
@@ -611,7 +611,7 @@ RefPtr<AST::Node> Parser::parse_if_expr()
             auto cbrace_error_start = push_start();
             if (!expect('}')) {
                 auto error_start = push_start();
-                RefPtr<AST::SyntaxError> syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end an 'if' true branch");
+                RefPtr<AST::SyntaxError> syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end an 'if' true branch", true);
                 if (body)
                     body->set_is_syntax_error(*syntax_error);
                 else
@@ -659,7 +659,7 @@ RefPtr<AST::Node> Parser::parse_subshell()
         auto cbrace_error_start = push_start();
         if (!expect('}')) {
             auto error_start = push_start();
-            RefPtr<AST::SyntaxError> syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a subshell");
+            RefPtr<AST::SyntaxError> syntax_error = create<AST::SyntaxError>("Expected a close brace '}' to end a subshell", true);
             if (body)
                 body->set_is_syntax_error(*syntax_error);
             else
@@ -684,7 +684,7 @@ RefPtr<AST::Node> Parser::parse_match_expr()
     auto match_expression = parse_expression();
     if (!match_expression) {
         return create<AST::MatchExpr>(
-            create<AST::SyntaxError>("Expected an expression after 'match'"),
+            create<AST::SyntaxError>("Expected an expression after 'match'", true),
             String {}, Optional<AST::Position> {}, Vector<AST::MatchEntry> {});
     }
 
@@ -701,7 +701,7 @@ RefPtr<AST::Node> Parser::parse_match_expr()
             auto node = create<AST::MatchExpr>(
                 match_expression.release_nonnull(),
                 String {}, move(as_position), Vector<AST::MatchEntry> {});
-            node->set_is_syntax_error(create<AST::SyntaxError>("Expected whitespace after 'as' in 'match'"));
+            node->set_is_syntax_error(create<AST::SyntaxError>("Expected whitespace after 'as' in 'match'", true));
             return node;
         }
 
@@ -710,7 +710,7 @@ RefPtr<AST::Node> Parser::parse_match_expr()
             auto node = create<AST::MatchExpr>(
                 match_expression.release_nonnull(),
                 String {}, move(as_position), Vector<AST::MatchEntry> {});
-            node->set_is_syntax_error(create<AST::SyntaxError>("Expected an identifier after 'as' in 'match'"));
+            node->set_is_syntax_error(create<AST::SyntaxError>("Expected an identifier after 'as' in 'match'", true));
             return node;
         }
     }
@@ -721,7 +721,7 @@ RefPtr<AST::Node> Parser::parse_match_expr()
         auto node = create<AST::MatchExpr>(
             match_expression.release_nonnull(),
             move(match_name), move(as_position), Vector<AST::MatchEntry> {});
-        node->set_is_syntax_error(create<AST::SyntaxError>("Expected an open brace '{' to start a 'match' entry list"));
+        node->set_is_syntax_error(create<AST::SyntaxError>("Expected an open brace '{' to start a 'match' entry list", true));
         return node;
     }
 
@@ -743,7 +743,7 @@ RefPtr<AST::Node> Parser::parse_match_expr()
         auto node = create<AST::MatchExpr>(
             match_expression.release_nonnull(),
             move(match_name), move(as_position), move(entries));
-        node->set_is_syntax_error(create<AST::SyntaxError>("Expected a close brace '}' to end a 'match' entry list"));
+        node->set_is_syntax_error(create<AST::SyntaxError>("Expected a close brace '}' to end a 'match' entry list", true));
         return node;
     }
 
@@ -761,7 +761,7 @@ AST::MatchEntry Parser::parse_match_entry()
 
     auto pattern = parse_match_pattern();
     if (!pattern)
-        return { {}, {}, {}, {}, create<AST::SyntaxError>("Expected a pattern in 'match' body") };
+        return { {}, {}, {}, {}, create<AST::SyntaxError>("Expected a pattern in 'match' body", true) };
 
     patterns.append(pattern.release_nonnull());
 
@@ -775,7 +775,7 @@ AST::MatchEntry Parser::parse_match_entry()
         consume_while(is_any_of(" \t\n"));
         auto pattern = parse_match_pattern();
         if (!pattern) {
-            error = create<AST::SyntaxError>("Expected a pattern to follow '|' in 'match' body");
+            error = create<AST::SyntaxError>("Expected a pattern to follow '|' in 'match' body", true);
             break;
         }
         consume_while(is_any_of(" \t\n"));
@@ -808,7 +808,7 @@ AST::MatchEntry Parser::parse_match_entry()
 
             if (!expect(')')) {
                 if (!error)
-                    error = create<AST::SyntaxError>("Expected a close paren ')' to end the identifier list of pattern 'as'");
+                    error = create<AST::SyntaxError>("Expected a close paren ')' to end the identifier list of pattern 'as'", true);
             }
         }
         consume_while(is_any_of(" \t\n"));
@@ -816,14 +816,14 @@ AST::MatchEntry Parser::parse_match_entry()
 
     if (!expect('{')) {
         if (!error)
-            error = create<AST::SyntaxError>("Expected an open brace '{' to start a match entry body");
+            error = create<AST::SyntaxError>("Expected an open brace '{' to start a match entry body", true);
     }
 
     auto body = parse_toplevel();
 
     if (!expect('}')) {
         if (!error)
-            error = create<AST::SyntaxError>("Expected a close brace '}' to end a match entry body");
+            error = create<AST::SyntaxError>("Expected a close brace '}' to end a match entry body", true);
     }
 
     if (body && error)
@@ -864,7 +864,7 @@ RefPtr<AST::Node> Parser::parse_redirection()
                     // Eat a character and hope the problem goes away
                     consume();
                 }
-                path = create<AST::SyntaxError>("Expected a path after redirection");
+                path = create<AST::SyntaxError>("Expected a path after redirection", true);
             }
             return create<AST::WriteAppendRedirection>(pipe_fd, path.release_nonnull()); // Redirection WriteAppend
         }
@@ -898,7 +898,7 @@ RefPtr<AST::Node> Parser::parse_redirection()
                 // Eat a character and hope the problem goes away
                 consume();
             }
-            path = create<AST::SyntaxError>("Expected a path after redirection");
+            path = create<AST::SyntaxError>("Expected a path after redirection", true);
         }
         return create<AST::WriteRedirection>(pipe_fd, path.release_nonnull()); // Redirection Write
     }
@@ -922,7 +922,7 @@ RefPtr<AST::Node> Parser::parse_redirection()
                 // Eat a character and hope the problem goes away
                 consume();
             }
-            path = create<AST::SyntaxError>("Expected a path after redirection");
+            path = create<AST::SyntaxError>("Expected a path after redirection", true);
         }
         if (mode == Read)
             return create<AST::ReadRedirection>(pipe_fd, path.release_nonnull()); // Redirection Read
@@ -1075,10 +1075,10 @@ RefPtr<AST::Node> Parser::parse_string()
         consume();
         auto inner = parse_doublequoted_string_inner();
         if (!inner)
-            inner = create<AST::SyntaxError>("Unexpected EOF in string");
+            inner = create<AST::SyntaxError>("Unexpected EOF in string", true);
         if (!expect('"')) {
             inner = create<AST::DoubleQuotedString>(move(inner));
-            inner->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating double quote"));
+            inner->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating double quote", true));
             return inner;
         }
         return create<AST::DoubleQuotedString>(move(inner)); // Double Quoted String
@@ -1092,7 +1092,7 @@ RefPtr<AST::Node> Parser::parse_string()
             is_error = true;
         auto result = create<AST::StringLiteral>(move(text)); // String Literal
         if (is_error)
-            result->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating single quote"));
+            result->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating single quote", true));
         return move(result);
     }
 
@@ -1229,16 +1229,16 @@ RefPtr<AST::Node> Parser::parse_evaluate()
         consume();
         auto inner = parse_pipe_sequence();
         if (!inner)
-            inner = create<AST::SyntaxError>("Unexpected EOF in list");
+            inner = create<AST::SyntaxError>("Unexpected EOF in list", true);
         if (!expect(')'))
-            inner->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating close paren"));
+            inner->set_is_syntax_error(*create<AST::SyntaxError>("Expected a terminating close paren", true));
 
         return create<AST::Execute>(inner.release_nonnull(), true);
     }
     auto inner = parse_expression();
 
     if (!inner) {
-        inner = create<AST::SyntaxError>("Expected a command");
+        inner = create<AST::SyntaxError>("Expected a command", true);
     } else {
         if (inner->is_list()) {
             auto execute_inner = create<AST::Execute>(inner.release_nonnull(), true);
@@ -1408,7 +1408,7 @@ RefPtr<AST::Node> Parser::parse_brace_expansion()
 
     if (auto spec = parse_brace_expansion_spec()) {
         if (!expect('}'))
-            spec->set_is_syntax_error(create<AST::SyntaxError>("Expected a close brace '}' to end a brace expansion"));
+            spec->set_is_syntax_error(create<AST::SyntaxError>("Expected a close brace '}' to end a brace expansion", true));
 
         return spec;
     }
@@ -1431,7 +1431,7 @@ RefPtr<AST::Node> Parser::parse_brace_expansion_spec()
                 return create<AST::Range>(start_expr.release_nonnull(), end_expr.release_nonnull());
             }
 
-            return create<AST::Range>(start_expr.release_nonnull(), create<AST::SyntaxError>("Expected an expression to end range brace expansion with"));
+            return create<AST::Range>(start_expr.release_nonnull(), create<AST::SyntaxError>("Expected an expression to end range brace expansion with", true));
         }
     }
 

Shell/Shell.cpp

@@ -1402,11 +1402,9 @@ bool Shell::read_single_line()
     if (line_result.is_error()) {
         if (line_result.error() == Line::Editor::Error::Eof || line_result.error() == Line::Editor::Error::Empty) {
             // Pretend the user tried to execute builtin_exit()
-            m_complete_line_builder.clear();
             run_command("exit");
             return read_single_line();
         } else {
-            m_complete_line_builder.clear();
             Core::EventLoop::current().quit(1);
             return false;
         }
@@ -1417,14 +1415,9 @@ bool Shell::read_single_line()
     if (line.is_empty())
         return true;
 
-    if (!m_complete_line_builder.is_empty())
-        m_complete_line_builder.append("\n");
-    m_complete_line_builder.append(line);
+    run_command(line);
 
-    run_command(m_complete_line_builder.string_view());
-
-    m_editor->add_to_history(m_complete_line_builder.build());
-    m_complete_line_builder.clear();
+    m_editor->add_to_history(line);
     return true;
 }
 
@@ -1599,6 +1592,14 @@ Shell::Shell(Line::Editor& editor)
     directory_stack.append(cwd);
     m_editor->load_history(get_history_path());
     cache_path();
+
+    m_editor->register_key_input_callback('\n', [](Line::Editor& editor) {
+        auto ast = Parser(editor.line()).parse();
+        if (ast && ast->is_syntax_error() && ast->syntax_error_node().is_continuable())
+            return true;
+
+        return EDITOR_INTERNAL_FUNCTION(finish)(editor);
+    });
 }
 
 Shell::~Shell()

Shell/Shell.h

@@ -244,7 +244,6 @@ private:
 #undef __ENUMERATE_SHELL_BUILTIN
     };
 
-    StringBuilder m_complete_line_builder;
     bool m_should_ignore_jobs_on_next_exit { false };
     pid_t m_pid { 0 };
 
@@ -267,6 +266,8 @@ private:
     RefPtr<Line::Editor> m_editor;
 
     bool m_default_constructed { false };
+
+    mutable bool m_last_continuation_state { false }; // false == not needed.
 };
 
 static constexpr bool is_word_character(char c)

Shell/main.cpp

@@ -61,6 +61,7 @@ int main(int argc, char** argv)
     });
 
     editor = Line::Editor::construct();
+    editor->initialize();
 
     auto shell = Shell::Shell::construct(*editor);
     s_shell = shell.ptr();
@@ -81,7 +82,6 @@ int main(int argc, char** argv)
     }
 #endif
 
-    editor->initialize();
     shell->termios = editor->termios();
     shell->default_termios = editor->default_termios();