AK+LibXML+JSSpecCompiler: Move LineTrackingLexer to AK

This is a simple extension of GenericLexer, and is used in more than
just LibXML, so let's move it into AK.
The move also resolves a FIXME, which is removed in this commit.

AK/GenericLexer.cpp

@@ -176,6 +176,31 @@ ErrorOr<T> GenericLexer::consume_decimal_integer()
     }
 }
 
+LineTrackingLexer::Position LineTrackingLexer::position_for(size_t index) const
+{
+    auto& [cached_index, cached_line, cached_column] = m_cached_position;
+
+    if (cached_index <= index) {
+        for (size_t i = cached_index; i < index; ++i) {
+            if (m_input[i] == '\n')
+                ++cached_line, cached_column = 0;
+            else
+                ++cached_column;
+        }
+    } else {
+        auto lines_backtracked = m_input.substring_view(index, cached_index - index).count('\n');
+        cached_line -= lines_backtracked;
+        if (lines_backtracked == 0) {
+            cached_column -= cached_index - index;
+        } else {
+            auto current_line_start = m_input.substring_view(0, index).find_last('\n').value_or(0);
+            cached_column = index - current_line_start;
+        }
+    }
+    cached_index = index;
+    return m_cached_position;
+}
+
 template ErrorOr<u8> GenericLexer::consume_decimal_integer<u8>();
 template ErrorOr<i8> GenericLexer::consume_decimal_integer<i8>();
 template ErrorOr<u16> GenericLexer::consume_decimal_integer<u16>();

AK/GenericLexer.h

@@ -234,6 +234,34 @@ private:
 #endif
 };
 
+class LineTrackingLexer : public GenericLexer {
+public:
+    using GenericLexer::GenericLexer;
+
+    struct Position {
+        size_t offset { 0 };
+        size_t line { 0 };
+        size_t column { 0 };
+    };
+
+    LineTrackingLexer(StringView input, Position start_position)
+        : GenericLexer(input)
+        , m_cached_position {
+            .line = start_position.line,
+            .column = start_position.column,
+        }
+    {
+    }
+
+    Position cached_position() const { return m_cached_position; }
+    void restore_cached_offset(Position cached_position) { m_cached_position = cached_position; }
+    Position position_for(size_t) const;
+    Position current_position() const { return position_for(m_index); }
+
+protected:
+    mutable Position m_cached_position;
+};
+
 constexpr auto is_any_of(StringView values)
 {
     return [values](auto c) { return values.contains(c); };
@@ -254,4 +282,5 @@ using AK::GenericLexer;
 using AK::is_any_of;
 using AK::is_path_separator;
 using AK::is_quote;
+using AK::LineTrackingLexer;
 #endif

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/Lexer.cpp

@@ -14,7 +14,7 @@
 namespace JSSpecCompiler {
 
 namespace {
-Optional<Token> consume_number(XML::LineTrackingLexer& lexer, Location& location)
+Optional<Token> consume_number(LineTrackingLexer& lexer, Location& location)
 {
     u64 start = lexer.tell();
 
@@ -73,14 +73,14 @@ void tokenize_string(SpecificationParsingContext& ctx, XML::Node const* node, St
         { "+"sv, TokenType::Plus },
     };
 
-    XML::LineTrackingLexer lexer(view, node->offset);
+    LineTrackingLexer lexer(view, node->offset);
 
     while (!lexer.is_eof()) {
         lexer.ignore_while(is_ascii_space);
 
         // FIXME: This is incorrect since we count text offset after XML reference resolution. To do
         //        this properly, we need support from XML::Parser.
-        Location token_location = ctx.location_from_xml_offset(lexer.offset_for(lexer.tell()));
+        Location token_location = ctx.location_from_xml_offset(lexer.position_for(lexer.tell()));
 
         if (auto result = consume_number(lexer, token_location); result.has_value()) {
             tokens.append(result.release_value());

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/SpecParser.cpp

@@ -50,12 +50,12 @@ Location SpecificationParsingContext::file_scope() const
     return { .filename = m_translation_unit->filename() };
 }
 
-Location SpecificationParsingContext::location_from_xml_offset(XML::Offset offset) const
+Location SpecificationParsingContext::location_from_xml_offset(LineTrackingLexer::Position position) const
 {
     return {
         .filename = m_translation_unit->filename(),
-        .line = offset.line,
+        .line = position.line,
-        .column = offset.column,
+        .column = position.column,
         .logical_location = m_current_logical_scope,
     };
 }

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/SpecParser.h

@@ -37,7 +37,7 @@ public:
     int step_list_nesting_level() const;
 
     Location file_scope() const;
-    Location location_from_xml_offset(XML::Offset offset) const;
+    Location location_from_xml_offset(LineTrackingLexer::Position position) const;
 
 private:
     TranslationUnitRef m_translation_unit;

Userland/Libraries/LibXML/DOM/Node.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/ByteString.h>
+#include <AK/GenericLexer.h>
 #include <AK/HashMap.h>
 #include <AK/Variant.h>
 #include <AK/Vector.h>
@@ -19,12 +20,6 @@ struct Attribute {
     ByteString value;
 };
 
-struct Offset {
-    size_t offset { 0 };
-    size_t line { 0 };
-    size_t column { 0 };
-};
-
 struct Node {
     struct Text {
         StringBuilder builder;
@@ -40,7 +35,7 @@ struct Node {
 
     bool operator==(Node const&) const;
 
-    Offset offset;
+    LineTrackingLexer::Position offset;
     Variant<Text, Comment, Element> content;
     Node* parent { nullptr };
 

Userland/Libraries/LibXML/Parser/Parser.cpp

@@ -66,31 +66,6 @@ consteval static auto set_to_search()
 
 namespace XML {
 
-Offset LineTrackingLexer::offset_for(size_t index) const
-{
-    auto& [cached_index, cached_line, cached_column] = m_cached_offset;
-
-    if (cached_index <= index) {
-        for (size_t i = cached_index; i < index; ++i) {
-            if (m_input[i] == '\n')
-                ++cached_line, cached_column = 0;
-            else
-                ++cached_column;
-        }
-    } else {
-        auto lines_backtracked = m_input.substring_view(index, cached_index - index).count('\n');
-        cached_line -= lines_backtracked;
-        if (lines_backtracked == 0) {
-            cached_column -= cached_index - index;
-        } else {
-            auto current_line_start = m_input.substring_view(0, index).find_last('\n').value_or(0);
-            cached_column = index - current_line_start;
-        }
-    }
-    cached_index = index;
-    return m_cached_offset;
-}
-
 size_t Parser::s_debug_indent_level { 0 };
 
 void Parser::append_node(NonnullOwnPtr<Node> node)
@@ -105,7 +80,7 @@ void Parser::append_node(NonnullOwnPtr<Node> node)
     }
 }
 
-void Parser::append_text(StringView text, Offset offset)
+void Parser::append_text(StringView text, LineTrackingLexer::Position position)
 {
     if (m_listener) {
         m_listener->text(text);
@@ -115,7 +90,7 @@ void Parser::append_text(StringView text, Offset offset)
     if (!m_entered_node) {
         Node::Text node;
         node.builder.append(text);
-        m_root_node = make<Node>(offset, move(node));
+        m_root_node = make<Node>(position, move(node));
         return;
     }
 
@@ -130,7 +105,7 @@ void Parser::append_text(StringView text, Offset offset)
             }
             Node::Text text_node;
             text_node.builder.append(text);
-            node.children.append(make<Node>(offset, move(text_node), m_entered_node));
+            node.children.append(make<Node>(position, move(text_node), m_entered_node));
         },
         [&](auto&) {
             // Can't enter a text or comment node.
@@ -138,7 +113,7 @@ void Parser::append_text(StringView text, Offset offset)
         });
 }
 
-void Parser::append_comment(StringView text, Offset offset)
+void Parser::append_comment(StringView text, LineTrackingLexer::Position position)
 {
     if (m_listener) {
         m_listener->comment(text);
@@ -152,7 +127,7 @@ void Parser::append_comment(StringView text, Offset offset)
 
     m_entered_node->content.visit(
         [&](Node::Element& node) {
-            node.children.append(make<Node>(offset, Node::Comment { text }, m_entered_node));
+            node.children.append(make<Node>(position, Node::Comment { text }, m_entered_node));
         },
         [&](auto&) {
             // Can't enter a text or comment node.
@@ -507,7 +482,7 @@ ErrorOr<void, ParseError> Parser::parse_comment()
     TRY(expect("-->"sv));
 
     if (m_options.preserve_comments)
-        append_comment(text, m_lexer.offset_for(comment_start));
+        append_comment(text, m_lexer.position_for(comment_start));
 
     rollback.disarm();
     return {};
@@ -699,7 +674,7 @@ ErrorOr<NonnullOwnPtr<Node>, ParseError> Parser::parse_empty_element_tag()
     TRY(expect("/>"sv));
 
     rollback.disarm();
-    return make<Node>(m_lexer.offset_for(tag_start), Node::Element { move(name), move(attributes), {} });
+    return make<Node>(m_lexer.position_for(tag_start), Node::Element { move(name), move(attributes), {} });
 }
 
 // 3.1.41. Attribute, https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-Attribute
@@ -851,7 +826,7 @@ ErrorOr<NonnullOwnPtr<Node>, ParseError> Parser::parse_start_tag()
     TRY(expect(">"sv));
 
     rollback.disarm();
-    return make<Node>(m_lexer.offset_for(tag_start), Node::Element { move(name), move(attributes), {} });
+    return make<Node>(m_lexer.position_for(tag_start), Node::Element { move(name), move(attributes), {} });
 }
 
 // 3.1.42 ETag, https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-ETag
@@ -881,7 +856,7 @@ ErrorOr<void, ParseError> Parser::parse_content()
     // content ::= CharData? ((element | Reference | CDSect | PI | Comment) CharData?)*
     auto content_start = m_lexer.tell();
     if (auto result = parse_char_data(); !result.is_error())
-        append_text(result.release_value(), m_lexer.offset_for(content_start));
+        append_text(result.release_value(), m_lexer.position_for(content_start));
 
     while (true) {
         auto node_start = m_lexer.tell();
@@ -890,7 +865,7 @@ ErrorOr<void, ParseError> Parser::parse_content()
             goto try_char_data;
         if (auto result = parse_reference(); !result.is_error()) {
             auto reference = result.release_value();
-            auto reference_offset = m_lexer.offset_for(node_start);
+            auto reference_offset = m_lexer.position_for(node_start);
             if (auto char_reference = reference.get_pointer<ByteString>())
                 append_text(*char_reference, reference_offset);
             else
@@ -899,7 +874,7 @@ ErrorOr<void, ParseError> Parser::parse_content()
         }
         if (auto result = parse_cdata_section(); !result.is_error()) {
             if (m_options.preserve_cdata)
-                append_text(result.release_value(), m_lexer.offset_for(node_start));
+                append_text(result.release_value(), m_lexer.position_for(node_start));
             goto try_char_data;
         }
         if (auto result = parse_processing_instruction(); !result.is_error())
@@ -911,7 +886,7 @@ ErrorOr<void, ParseError> Parser::parse_content()
 
     try_char_data:;
         if (auto result = parse_char_data(); !result.is_error())
-            append_text(result.release_value(), m_lexer.offset_for(node_start));
+            append_text(result.release_value(), m_lexer.position_for(node_start));
     }
 
     rollback.disarm();

Userland/Libraries/LibXML/Parser/Parser.h

@@ -39,29 +39,6 @@ struct Listener {
     virtual void error(ParseError const&) { }
 };
 
-// FIXME: This is also used in JSSpecCompiler, so should probably live in AK or even merged with
-//        AK::GenericLexer.
-class LineTrackingLexer : public GenericLexer {
-public:
-    using GenericLexer::GenericLexer;
-
-    LineTrackingLexer(StringView input, XML::Offset start_offset)
-        : GenericLexer(input)
-        , m_cached_offset {
-            .line = start_offset.line,
-            .column = start_offset.column,
-        }
-    {
-    }
-
-    Offset cached_offset() const { return m_cached_offset; }
-    void restore_cached_offset(Offset cached_offset) { m_cached_offset = cached_offset; }
-    Offset offset_for(size_t) const;
-
-protected:
-    mutable Offset m_cached_offset;
-};
-
 class Parser {
 public:
     struct Options {
@@ -96,8 +73,8 @@ private:
 
     ErrorOr<void, ParseError> parse_internal();
     void append_node(NonnullOwnPtr<Node>);
-    void append_text(StringView, Offset);
+    void append_text(StringView, LineTrackingLexer::Position);
-    void append_comment(StringView, Offset);
+    void append_comment(StringView, LineTrackingLexer::Position);
     void enter_node(Node&);
     void leave_node();
 
@@ -170,9 +147,9 @@ private:
     [[nodiscard]] auto rollback_point(SourceLocation location = SourceLocation::current())
     {
         return ArmedScopeGuard {
-            [this, position = m_lexer.tell(), cached_offset = m_lexer.cached_offset(), location] {
+            [this, position = m_lexer.tell(), cached_position = m_lexer.cached_position(), location] {
                 m_lexer.retreat(m_lexer.tell() - position);
-                m_lexer.restore_cached_offset(cached_offset);
+                m_lexer.restore_cached_offset(cached_position);
                 (void)location;
                 dbgln_if(XML_PARSER_DEBUG, "{:->{}}FAIL @ {} -- \x1b[31m{}\x1b[0m", " ", s_debug_indent_level * 2, location, m_lexer.remaining().substring_view(0, min(16, m_lexer.tell_remaining())).replace("\n"sv, "\\n"sv, ReplaceMode::All));
             }