Shell: Add support for regex match patterns

We previously allowed globs as match pattern, but for more complex
matching needs, it's nice to have regular expressions.
And as the existing "name a part of the match" concept maps nicely to
named capture groups, we can simply reuse the same code and make groups
with names available in the match body.

Userland/Shell/AST.cpp

@@ -2117,8 +2117,15 @@ void MatchExpr::dump(int level) const
             builder.append(')');
         }
         print_indented(builder.string_view(), level + 2);
-        for (auto& node : entry.options)
-            node.dump(level + 3);
+        entry.options.visit(
+            [&](NonnullRefPtrVector<Node> const& options) {
+                for (auto& option : options)
+                    option.dump(level + 3);
+            },
+            [&](Vector<Regex<ECMA262>> const& options) {
+                for (auto& option : options)
+                    print_indented(String::formatted("(regex: {})", option.pattern_value), level + 3);
+            });
         print_indented("(execute)", level + 2);
         if (entry.body)
             entry.body->dump(level + 3);
@@ -2136,6 +2143,21 @@ RefPtr<Value> MatchExpr::run(RefPtr<Shell> shell)
     auto list = value->resolve_as_list(shell);
 
     auto list_matches = [&](auto&& pattern, auto& spans) {
+        if constexpr (IsSame<RemoveCVReference<decltype(pattern)>, Regex<ECMA262>>) {
+            if (list.size() != 1)
+                return false;
+            auto& subject = list.first();
+            auto match = pattern.match(subject);
+            if (!match.success)
+                return false;
+
+            spans.ensure_capacity(match.n_capture_groups);
+            for (size_t i = 0; i < match.n_capture_groups; ++i) {
+                auto& capture = match.capture_group_matches[0][i];
+                spans.append(capture.view.to_string());
+            }
+            return true;
+        } else {
             if (pattern.size() != list.size())
                 return false;
 
@@ -2148,9 +2170,13 @@ RefPtr<Value> MatchExpr::run(RefPtr<Shell> shell)
             }
 
             return true;
+        }
     };
 
-    auto resolve_pattern = [&](auto& option) {
+    auto resolve_pattern = [&](auto& option) -> decltype(auto) {
+        if constexpr (IsSame<RemoveCVReference<decltype(option)>, Regex<ECMA262>>) {
+            return option;
+        } else {
             Vector<String> pattern;
             if (option.is_glob()) {
                 pattern.append(static_cast<const Glob*>(&option)->text());
@@ -2169,6 +2195,7 @@ RefPtr<Value> MatchExpr::run(RefPtr<Shell> shell)
             }
 
             return pattern;
+        }
     };
 
     auto frame = shell->push_frame(String::formatted("match ({})", this));
@@ -2176,7 +2203,8 @@ RefPtr<Value> MatchExpr::run(RefPtr<Shell> shell)
         shell->set_local_variable(m_expr_name, value, true);
 
     for (auto& entry : m_entries) {
-        for (auto& option : entry.options) {
+        auto result = entry.options.visit([&](auto& options) -> Variant<IterationDecision, RefPtr<Value>> {
+            for (auto& option : options) {
                 Vector<String> spans;
                 if (list_matches(resolve_pattern(option), spans)) {
                     if (entry.body) {
@@ -2189,11 +2217,17 @@ RefPtr<Value> MatchExpr::run(RefPtr<Shell> shell)
                             }
                         }
                         return entry.body->run(shell);
-                } else {
-                    return make_ref_counted<AST::ListValue>({});
-                }
+                    }
+                    return RefPtr<Value>(make_ref_counted<AST::ListValue>({}));
                 }
             }
+            return IterationDecision::Continue;
+        });
+        if (result.has<IterationDecision>() && result.get<IterationDecision>() == IterationDecision::Break)
+            break;
+
+        if (result.has<RefPtr<Value>>())
+            return move(result).get<RefPtr<Value>>();
     }
 
     shell->raise_error(Shell::ShellError::EvaluatedSyntaxError, "Non-exhaustive match rules!", position());
@@ -2211,8 +2245,12 @@ void MatchExpr::highlight_in_editor(Line::Editor& editor, Shell& shell, Highligh
 
     for (auto& entry : m_entries) {
         metadata.is_first_in_list = false;
-        for (auto& option : entry.options)
+        entry.options.visit(
+            [&](NonnullRefPtrVector<Node>& node_options) {
+                for (auto& option : node_options)
                     option.highlight_in_editor(editor, shell, metadata);
+            },
+            [](auto&) {});
 
         metadata.is_first_in_list = true;
         if (entry.body)

Userland/Shell/AST.h

@@ -17,6 +17,7 @@
 #include <AK/Types.h>
 #include <AK/Vector.h>
 #include <LibLine/Editor.h>
+#include <LibRegex/Regex.h>
 
 namespace Shell::AST {
 
@@ -1051,7 +1052,7 @@ private:
 };
 
 struct MatchEntry {
-    NonnullRefPtrVector<Node> options;
+    Variant<NonnullRefPtrVector<Node>, Vector<Regex<ECMA262>>> options;
     Optional<Vector<String>> match_names;
     Optional<Position> match_as_position;
     Vector<Position> pipe_positions;

Userland/Shell/Formatter.cpp

@@ -583,12 +583,24 @@ void Formatter::visit(const AST::MatchExpr* node)
                 insert_separator();
             first_entry = false;
             auto first = true;
-            for (auto& option : entry.options) {
+            entry.options.visit(
+                [&](NonnullRefPtrVector<AST::Node> const& patterns) {
+                    for (auto& option : patterns) {
                         if (!first)
                             current_builder().append(" | ");
                         first = false;
                         option.visit(*this);
                     }
+                },
+                [&](Vector<Regex<ECMA262>> const& patterns) {
+                    for (auto& option : patterns) {
+                        if (!first)
+                            current_builder().append(" | ");
+                        first = false;
+                        auto node = make_ref_counted<AST::BarewordLiteral>(AST::Position {}, option.pattern_value);
+                        node->visit(*this);
+                    }
+                });
 
             current_builder().append(' ');
             if (entry.match_names.has_value() && !entry.match_names.value().is_empty()) {

Userland/Shell/NodeVisitor.cpp

@@ -141,8 +141,10 @@ void NodeVisitor::visit(const AST::MatchExpr* node)
 {
     node->matched_expr()->visit(*this);
     for (auto& entry : node->entries()) {
-        for (auto& option : entry.options)
+        if (auto* ptr = entry.options.get_pointer<NonnullRefPtrVector<Node>>()) {
+            for (auto& option : *ptr)
                 option.visit(*this);
+        }
         if (entry.body)
             entry.body->visit(*this);
     }

Userland/Shell/Parser.cpp

@@ -84,9 +84,9 @@ bool Parser::expect(StringView expected)
 }
 
 template<typename A, typename... Args>
-NonnullRefPtr<A> Parser::create(Args... args)
+NonnullRefPtr<A> Parser::create(Args&&... args)
 {
-    return adopt_ref(*new A(AST::Position { m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() }, args...));
+    return adopt_ref(*new A(AST::Position { m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() }, forward<Args>(args)...));
 }
 
 [[nodiscard]] OwnPtr<Parser::ScopedOffset> Parser::push_start()
@@ -892,10 +892,10 @@ RefPtr<AST::Node> Parser::parse_match_expr()
     for (;;) {
         auto entry = parse_match_entry();
         consume_while(is_any_of(" \t\n"));
-        if (entry.options.is_empty())
+        if (entry.options.visit([](auto& x) { return x.is_empty(); }))
             break;
 
-        entries.append(entry);
+        entries.append(move(entry));
     }
 
     consume_while(is_any_of(" \t\n"));
@@ -916,15 +916,32 @@ AST::MatchEntry Parser::parse_match_entry()
     auto rule_start = push_start();
 
     NonnullRefPtrVector<AST::Node> patterns;
+    Vector<Regex<ECMA262>> regexps;
     Vector<AST::Position> pipe_positions;
     Optional<Vector<String>> match_names;
     Optional<AST::Position> match_as_position;
+    enum {
+        Regex,
+        Glob,
+    } pattern_kind;
 
-    auto pattern = parse_match_pattern();
-    if (!pattern)
-        return { {}, {}, {}, {}, create<AST::SyntaxError>("Expected a pattern in 'match' body", true) };
+    consume_while(is_any_of(" \t\n"));
 
-    patterns.append(pattern.release_nonnull());
+    auto regex_pattern = parse_regex_pattern();
+    if (regex_pattern.has_value()) {
+        if (auto error = regex_pattern.value().parser_result.error; error != regex::Error::NoError)
+            return { NonnullRefPtrVector<AST::Node> {}, {}, {}, {}, create<AST::SyntaxError>(regex::get_error_string(error), false) };
+
+        pattern_kind = Regex;
+        regexps.append(regex_pattern.release_value());
+    } else {
+        auto glob_pattern = parse_match_pattern();
+        if (!glob_pattern)
+            return { NonnullRefPtrVector<AST::Node> {}, {}, {}, {}, create<AST::SyntaxError>("Expected a pattern in 'match' body", true) };
+
+        pattern_kind = Glob;
+        patterns.append(glob_pattern.release_nonnull());
+    }
 
     consume_while(is_any_of(" \t\n"));
 
@@ -934,14 +951,28 @@ AST::MatchEntry Parser::parse_match_entry()
     while (expect('|')) {
         pipe_positions.append({ previous_pipe_start_position, m_offset, previous_pipe_start_line, line() });
         consume_while(is_any_of(" \t\n"));
+        switch (pattern_kind) {
+        case Regex: {
+            auto pattern = parse_regex_pattern();
+            if (!pattern.has_value()) {
+                error = create<AST::SyntaxError>("Expected a regex pattern to follow '|' in 'match' body", true);
+                break;
+            }
+            regexps.append(pattern.release_value());
+            break;
+        }
+        case Glob: {
             auto pattern = parse_match_pattern();
             if (!pattern) {
                 error = create<AST::SyntaxError>("Expected a pattern to follow '|' in 'match' body", true);
                 break;
             }
-        consume_while(is_any_of(" \t\n"));
-
             patterns.append(pattern.release_nonnull());
+            break;
+        }
+        }
+
+        consume_while(is_any_of(" \t\n"));
 
         previous_pipe_start_line = line();
         previous_pipe_start_position = m_offset;
@@ -951,7 +982,7 @@ AST::MatchEntry Parser::parse_match_entry()
 
     auto as_start_position = m_offset;
     auto as_start_line = line();
-    if (expect("as")) {
+    if (pattern_kind == Glob && expect("as")) {
         match_as_position = AST::Position { as_start_position, m_offset, as_start_line, line() };
         consume_while(is_any_of(" \t\n"));
         if (!expect('(')) {
@@ -975,6 +1006,31 @@ AST::MatchEntry Parser::parse_match_entry()
         consume_while(is_any_of(" \t\n"));
     }
 
+    if (pattern_kind == Regex) {
+        Vector<String> names;
+        for (auto& regex : regexps) {
+            if (names.is_empty()) {
+                for (auto& name : regex.parser_result.capture_groups)
+                    names.append(name);
+            } else {
+                size_t index = 0;
+                for (auto& name : regex.parser_result.capture_groups) {
+                    if (names.size() <= index) {
+                        names.append(name);
+                        continue;
+                    }
+
+                    if (names[index] != name) {
+                        if (!error)
+                            error = create<AST::SyntaxError>("Alternative regex patterns must have the same capture groups", false);
+                        break;
+                    }
+                }
+            }
+        }
+        match_names = move(names);
+    }
+
     if (!expect('{')) {
         if (!error)
             error = create<AST::SyntaxError>("Expected an open brace '{' to start a match entry body", true);
@@ -992,7 +1048,10 @@ AST::MatchEntry Parser::parse_match_entry()
     else if (error)
         body = error;
 
+    if (pattern_kind == Glob)
         return { move(patterns), move(match_names), move(match_as_position), move(pipe_positions), move(body) };
+
+    return { move(regexps), move(match_names), move(match_as_position), move(pipe_positions), move(body) };
 }
 
 RefPtr<AST::Node> Parser::parse_match_pattern()
@@ -1000,6 +1059,36 @@ RefPtr<AST::Node> Parser::parse_match_pattern()
     return parse_expression();
 }
 
+Optional<Regex<ECMA262>> Parser::parse_regex_pattern()
+{
+    auto rule_start = push_start();
+
+    auto start = m_offset;
+    if (!expect("(?:") && !expect("(?<"))
+        return {};
+
+    size_t open_parens = 1;
+    while (open_parens > 0) {
+        if (at_end())
+            break;
+
+        if (next_is("("))
+            ++open_parens;
+        else if (next_is(")"))
+            --open_parens;
+        consume();
+    }
+
+    if (open_parens != 0) {
+        restore_to(*rule_start);
+        return {};
+    }
+
+    auto end = m_offset;
+    auto pattern = m_input.substring_view(start, end - start);
+    return Regex<ECMA262>(pattern);
+}
+
 RefPtr<AST::Node> Parser::parse_redirection()
 {
     auto rule_start = push_start();

Userland/Shell/Parser.h

@@ -25,7 +25,7 @@ public:
 
     RefPtr<AST::Node> parse();
     /// Parse the given string *as* an expression
-    /// that is to forefully enclose it in double-quotes.
+    /// that is to forcefully enclose it in double-quotes.
     RefPtr<AST::Node> parse_as_single_expression();
     NonnullRefPtrVector<AST::Node> parse_as_multiple_expressions();
 
@@ -77,6 +77,7 @@ private:
     RefPtr<AST::Node> parse_match_expr();
     AST::MatchEntry parse_match_entry();
     RefPtr<AST::Node> parse_match_pattern();
+    Optional<Regex<ECMA262>> parse_regex_pattern();
     RefPtr<AST::Node> parse_redirection();
     RefPtr<AST::Node> parse_list_expression();
     RefPtr<AST::Node> parse_expression();
@@ -98,7 +99,7 @@ private:
     bool parse_heredoc_entries();
 
     template<typename A, typename... Args>
-    NonnullRefPtr<A> create(Args... args);
+    NonnullRefPtr<A> create(Args&&... args);
 
     void set_end_condition(OwnPtr<Function<bool()>> condition) { m_end_condition = move(condition); }
     bool at_end() const
@@ -228,11 +229,16 @@ subshell :: '{' toplevel '}'
 match_expr :: 'match' ws+ expression ws* ('as' ws+ identifier)? '{' match_entry* '}'
 
 match_entry :: match_pattern ws* (as identifier_list)? '{' toplevel '}'
+             | regex_pattern ws* '{' toplevel '}'
 
 identifier_list :: '(' (identifier ws*)* ')'
 
+regex_pattern :: regex_pattern (ws* '|' ws* regex_pattern)*
+
 match_pattern          :: expression (ws* '|' ws* expression)*
 
+regex_pattern :: '(?:' .* ')' { enclosed string must contain balanced parentheses }
+
 command :: redirection command
          | list_expression command?