Start tracking element nesting in external scanner

Co-Authored-By: Ashi Krishan <queerviolet@github.com>

binding.gyp

@@ -8,6 +8,7 @@
       ],
       "sources": [
         "src/parser.c",
+        "src/scanner.cc",
         "src/binding.cc"
       ],
       "cflags_c": [

corpus/main.txt

@@ -6,9 +6,9 @@ Tags
 
 (fragment
   (element
-    (start_tag (tag_name))
+    (start_tag)
     (text)
-    (end_tag (tag_name))))
+    (end_tag)))
 
 ===================================
 Tags with attributes
@@ -17,9 +17,8 @@ Tags with attributes
 ---
 
 (fragment
-  (void_element
-    (void_start_tag
-      (void_tag_name)
+  (element
+    (start_tag
       (attribute
         (attribute_name)
         (attribute_value))
@@ -28,7 +27,7 @@ Tags with attributes
         (quoted_attribute_value (attribute_value)))
       (attribute
         (attribute_name)))
-    (end_tag (tag_name))))
+    (end_tag)))
 
 ===================================
 Nested tags
@@ -42,37 +41,33 @@ Nested tags
 
 (fragment
   (element
-    (start_tag (tag_name))
+    (start_tag)
+    (element
+      (start_tag)
+      (text)
+      (end_tag))
     (text)
     (element
-      (start_tag (tag_name))
+      (start_tag)
       (text)
-      (end_tag (tag_name)))
-    (text)
-    (element
-      (start_tag (tag_name))
-      (text)
-      (end_tag (tag_name)))
-    (text)
-    (end_tag (tag_name))))
+      (end_tag))
+    (end_tag)))
 
 ==================================
 Void tags
 ==================================
-<form><img src="somethign.png"><br><input type=submit value=Ok /></form>
+<form><img src="something.png"><br><input type=submit value=Ok /></form>
 ---
 
 (fragment
   (element
-    (start_tag (tag_name))
-    (void_element
-      (void_start_tag
-        (tag_name)
+    (start_tag)
+    (element
+      (start_tag
         (attribute (attribute_name) (quoted_attribute_value (attribute_value)))))
-    (void_element (void_start_tag (tag_name)))
-    (void_element
+    (element (start_tag))
+    (element
       (self_closing_tag
-        (tag_name)
         (attribute (attribute_name) (attribute_value))
         (attribute (attribute_name) (attribute_value))))
-    (end_tag (tag_name))))
+    (end_tag)))

grammar.js

@@ -1,16 +1,13 @@
-const startTag = ($, tag) => seq(
-  '<',
-  alias(tag, $.tag_name),
-  repeat($.attribute),
-  '>'
-)
-
 module.exports = grammar({
   name: 'html',
 
   externals: $ => [
-    $.tag_name,
-
+    $._open_start_tag,
+    $._close_start_tag,
+    $._self_close_start_tag,
+    $.end_tag,
+    $._implicit_end_tag,
+    $._erroneous_end_tag,
   ],
 
   rules: {
@@ -18,31 +15,29 @@ module.exports = grammar({
 
     _node: $ => choice(
       $.text,
-      $.element,
-      $.void_element
+      $._erroneous_end_tag,
+      $.element
     ),
 
-    element: $ => seq(
+    element: $ => choice(
+      seq(
         $.start_tag,
         repeat($._node),
-      $.end_tag
+        choice($.end_tag, $._implicit_end_tag)
       ),
-
-    void_element: $ => choice(
-      seq($.void_start_tag, optional($.end_tag)),
       $.self_closing_tag
     ),
 
-    start_tag: $ => startTag($, $.tag_name),
-
-    void_start_tag: $ => startTag($, $.void_tag_name),
+    start_tag: $ => seq(
+      $._open_start_tag,
+      repeat($.attribute),
+      $._close_start_tag
+    ),
 
     self_closing_tag: $ => seq(
-      '<',
-      choice($.tag_name, $.void_tag_name),
+      $._open_start_tag,
       repeat($.attribute),
-      '/',
-      '>'
+      $._self_close_start_tag
     ),
 
     attribute: $ => seq(
@@ -63,40 +58,6 @@ module.exports = grammar({
       seq('"', optional(alias(/[^"]+/, $.attribute_value)), '"')
     ),
 
-    end_tag: $ => seq(
-      '</',
-      choice($.tag_name, $.void_tag_name),
-      '>'
-    ),
-
-    tag_name: $ => /[a-zA-Z\-]+/,
-
-    void_tag_name: $ => token(prec(1, choice(
-      'area',
-      'base',
-      'basefont',
-      'bgsound',
-      'br',
-      'col',
-      'command',
-      'embed',
-      'frame',
-      'hr',
-      'image',
-      'img',
-      'input',
-      'isindex',
-      'keygen',
-      'link',
-      'menuitem',
-      'meta',
-      'nextid',
-      'param',
-      'source',
-      'track',
-      'wbr'
-    ))),
-
     text: $ => /[^<>]+/
   }
 });

src/grammar.json

@@ -17,15 +17,18 @@
         },
         {
           "type": "SYMBOL",
-          "name": "element"
+          "name": "_erroneous_end_tag"
         },
         {
           "type": "SYMBOL",
-          "name": "void_element"
+          "name": "element"
         }
       ]
     },
     "element": {
+      "type": "CHOICE",
+      "members": [
+        {
           "type": "SEQ",
           "members": [
             {
@@ -40,17 +43,19 @@
               }
             },
             {
-          "type": "SYMBOL",
-          "name": "end_tag"
-        }
-      ]
-    },
-    "void_element": {
               "type": "CHOICE",
               "members": [
                 {
                   "type": "SYMBOL",
-          "name": "void_start_tag"
+                  "name": "end_tag"
+                },
+                {
+                  "type": "SYMBOL",
+                  "name": "_implicit_end_tag"
+                }
+              ]
+            }
+          ]
         },
         {
           "type": "SYMBOL",
@@ -62,17 +67,8 @@
       "type": "SEQ",
       "members": [
         {
-          "type": "STRING",
-          "value": "<"
-        },
-        {
-          "type": "ALIAS",
-          "content": {
           "type": "SYMBOL",
-            "name": "tag_name"
-          },
-          "named": true,
-          "value": "tag_name"
+          "name": "_open_start_tag"
         },
         {
           "type": "REPEAT",
@@ -82,59 +78,17 @@
           }
         },
         {
-          "type": "STRING",
-          "value": ">"
-        }
-      ]
-    },
-    "void_start_tag": {
-      "type": "SEQ",
-      "members": [
-        {
-          "type": "STRING",
-          "value": "<"
-        },
-        {
-          "type": "ALIAS",
-          "content": {
           "type": "SYMBOL",
-            "name": "void_tag_name"
-          },
-          "named": true,
-          "value": "tag_name"
-        },
-        {
-          "type": "REPEAT",
-          "content": {
-            "type": "SYMBOL",
-            "name": "attribute"
-          }
-        },
-        {
-          "type": "STRING",
-          "value": ">"
+          "name": "_close_start_tag"
         }
       ]
     },
     "self_closing_tag": {
       "type": "SEQ",
-      "members": [
-        {
-          "type": "STRING",
-          "value": "<"
-        },
-        {
-          "type": "CHOICE",
       "members": [
         {
           "type": "SYMBOL",
-              "name": "tag_name"
-            },
-            {
-              "type": "SYMBOL",
-              "name": "void_tag_name"
-            }
-          ]
+          "name": "_open_start_tag"
         },
         {
           "type": "REPEAT",
@@ -144,12 +98,8 @@
           }
         },
         {
-          "type": "STRING",
-          "value": "/"
-        },
-        {
-          "type": "STRING",
-          "value": ">"
+          "type": "SYMBOL",
+          "name": "_self_close_start_tag"
         }
       ]
     },
@@ -271,135 +221,6 @@
         }
       ]
     },
-    "end_tag": {
-      "type": "SEQ",
-      "members": [
-        {
-          "type": "STRING",
-          "value": "<"
-        },
-        {
-          "type": "STRING",
-          "value": "/"
-        },
-        {
-          "type": "SYMBOL",
-          "name": "tag_name"
-        },
-        {
-          "type": "STRING",
-          "value": ">"
-        }
-      ]
-    },
-    "tag_name": {
-      "type": "PATTERN",
-      "value": "[a-zA-Z\\-]+"
-    },
-    "void_tag_name": {
-      "type": "TOKEN",
-      "content": {
-        "type": "PREC",
-        "value": 1,
-        "content": {
-          "type": "CHOICE",
-          "members": [
-            {
-              "type": "STRING",
-              "value": "area"
-            },
-            {
-              "type": "STRING",
-              "value": "base"
-            },
-            {
-              "type": "STRING",
-              "value": "basefont"
-            },
-            {
-              "type": "STRING",
-              "value": "bgsound"
-            },
-            {
-              "type": "STRING",
-              "value": "br"
-            },
-            {
-              "type": "STRING",
-              "value": "col"
-            },
-            {
-              "type": "STRING",
-              "value": "command"
-            },
-            {
-              "type": "STRING",
-              "value": "embed"
-            },
-            {
-              "type": "STRING",
-              "value": "frame"
-            },
-            {
-              "type": "STRING",
-              "value": "hr"
-            },
-            {
-              "type": "STRING",
-              "value": "image"
-            },
-            {
-              "type": "STRING",
-              "value": "img"
-            },
-            {
-              "type": "STRING",
-              "value": "input"
-            },
-            {
-              "type": "STRING",
-              "value": "isindex"
-            },
-            {
-              "type": "STRING",
-              "value": "keygen"
-            },
-            {
-              "type": "STRING",
-              "value": "link"
-            },
-            {
-              "type": "STRING",
-              "value": "menuitem"
-            },
-            {
-              "type": "STRING",
-              "value": "meta"
-            },
-            {
-              "type": "STRING",
-              "value": "nextid"
-            },
-            {
-              "type": "STRING",
-              "value": "param"
-            },
-            {
-              "type": "STRING",
-              "value": "source"
-            },
-            {
-              "type": "STRING",
-              "value": "track"
-            },
-            {
-              "type": "STRING",
-              "value": "wbr"
-            }
-          ]
-        }
-      }
-    },
     "text": {
       "type": "PATTERN",
       "value": "[^<>]+"
@@ -412,6 +233,31 @@
     }
   ],
   "conflicts": [],
-  "externals": [],
+  "externals": [
+    {
+      "type": "SYMBOL",
+      "name": "_open_start_tag"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_close_start_tag"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_self_close_start_tag"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "end_tag"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_implicit_end_tag"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_erroneous_end_tag"
+    }
+  ],
   "inline": []
 }

src/scanner.cc

@@ -0,0 +1,185 @@
+#include <tree_sitter/parser.h>
+#include <algorithm>
+#include <vector>
+#include <string>
+#include <locale>
+
+#include "tag.h"
+
+namespace {
+
+using std::vector;
+using std::string;
+
+enum TokenType {
+  OPEN_START_TAG,
+  CLOSE_START_TAG,
+  SELF_CLOSE_START_TAG,
+  END_TAG,
+  IMPLICIT_END_TAG,
+  ERRONEOUS_END_TAG,
+};
+
+struct Scanner {
+  Scanner() {}
+
+  unsigned serialize(char *buffer) {
+    unsigned i = 0;
+    for (Tag &tag : tags) {
+      buffer[i] = static_cast<char>(tag.type);
+      i++;
+
+      if (tag.type == CUSTOM) {
+        buffer[i++] = tag.custom_tag_name.size();
+        for (char c : tag.custom_tag_name) {
+          buffer[i++] = c;
+        }
+      }
+    }
+
+    return i;
+  }
+
+  void deserialize(const char *buffer, unsigned length) {
+    tags.clear();
+
+    unsigned i = 0;
+    while (i < length) {
+      Tag tag { static_cast<TagType>(buffer[i]), "" };
+      i++;
+      if (tag.type == CUSTOM) {
+        tag.custom_tag_name.resize(buffer[i++]);
+        for (unsigned j = 0; j < tag.custom_tag_name.size(); j++) {
+          tag.custom_tag_name[j] = buffer[i++];
+        }
+      }
+      tags.push_back(tag);
+    }
+  }
+
+  string scan_tag_name(TSLexer *lexer) {
+    string tag_name;
+    while (iswalpha(lexer->lookahead) || lexer->lookahead == '-' || lexer->lookahead == ':') {
+      tag_name += std::toupper(lexer->lookahead);
+      lexer->advance(lexer, false);
+    }
+    return tag_name;
+  }
+
+  bool start_tag(TSLexer *lexer) {
+    auto tag_name = scan_tag_name(lexer);
+    if (tag_name.empty()) return false;
+
+    Tag tag = Tag::for_name(tag_name);
+    tags.push_back(tag);
+
+    lexer->mark_end(lexer);
+    lexer->result_symbol = OPEN_START_TAG;
+    return true;
+  }
+
+  bool end_tag(TSLexer *lexer) {
+    auto tag_name = scan_tag_name(lexer);
+    if (tag_name.empty()) return false;
+
+    lexer->advance(lexer, false);
+
+    Tag tag = Tag::for_name(tag_name);
+
+    // The tag correctly closes the topmost element on the stack
+    if (tag == tags.back()) {
+      tags.pop_back();
+      lexer->mark_end(lexer);
+      lexer->result_symbol = END_TAG;
+      return true;
+    }
+
+    // Otherwise, dig deeper and queue implicit end tags (to be nice in
+    // the case of malformed HTML)
+    if (std::find(tags.begin(), tags.end(), tag) != tags.end()) {
+      tags.pop_back();
+      lexer->result_symbol = IMPLICIT_END_TAG;
+      return true;
+    }
+
+    // You closed a tag you never opened 😭
+    lexer->mark_end(lexer);
+    lexer->result_symbol = ERRONEOUS_END_TAG;
+    return true;
+  }
+
+  bool scan(TSLexer *lexer, const bool *valid_symbols) {
+    while (iswspace(lexer->lookahead)) {
+      lexer->advance(lexer, true);
+    }
+
+    switch (lexer->lookahead) {
+      case '<':
+        if (valid_symbols[OPEN_START_TAG] || valid_symbols[END_TAG]) {
+          lexer->mark_end(lexer);
+          lexer->advance(lexer, false);
+          if (lexer->lookahead == '/') {
+            lexer->advance(lexer, false);
+            return end_tag(lexer);
+          }
+          return start_tag(lexer);
+        }
+        break;
+
+      case '>':
+        if (valid_symbols[CLOSE_START_TAG]) {
+          lexer->advance(lexer, false);
+          lexer->result_symbol = CLOSE_START_TAG;
+          return true;
+        }
+        break;
+
+      case '/':
+        if (valid_symbols[SELF_CLOSE_START_TAG]) {
+          lexer->advance(lexer, false);
+          if (lexer->lookahead == '>') {
+            lexer->advance(lexer, false);
+            tags.pop_back();
+            lexer->result_symbol = SELF_CLOSE_START_TAG;
+            return true;
+          }
+        }
+        break;
+    }
+
+    return false;
+  }
+
+  vector<Tag> tags;
+};
+
+}
+
+extern "C" {
+
+void *tree_sitter_html_external_scanner_create() {
+  return new Scanner();
+}
+
+bool tree_sitter_html_external_scanner_scan(void *payload, TSLexer *lexer,
+                                            const bool *valid_symbols) {
+  Scanner *scanner = static_cast<Scanner *>(payload);
+  return scanner->scan(lexer, valid_symbols);
+}
+
+unsigned tree_sitter_html_external_scanner_serialize(void *payload, char *buffer) {
+  Scanner *scanner = static_cast<Scanner *>(payload);
+  return scanner->serialize(buffer);
+}
+
+void tree_sitter_html_external_scanner_deserialize(void *payload, const char *buffer, unsigned length) {
+  Scanner *scanner = static_cast<Scanner *>(payload);
+  scanner->deserialize(buffer, length);
+}
+
+void tree_sitter_html_external_scanner_destroy(void *payload) {
+  Scanner *scanner = static_cast<Scanner *>(payload);
+  delete scanner;
+}
+
+}

src/tag.h

@@ -0,0 +1,296 @@
+#include <string>
+#include <unordered_map>
+
+using std::string;
+using std::unordered_map;
+
+enum TagType : char {
+  // Void tags
+  AREA,
+  BASE,
+  BASEFONT,
+  BGSOUND,
+  BR,
+  COL,
+  COMMAND,
+  EMBED,
+  FRAME,
+  HR,
+  IMAGE,
+  IMG,
+  INPUT,
+  ISINDEX,
+  KEYGEN,
+  LINK,
+  MENUITEM,
+  META,
+  NEXTID,
+  PARAM,
+  SOURCE,
+  TRACK,
+  WBR,
+  END_OF_VOID_TAGS,
+
+  A,
+  ABBR,
+  ADDRESS,
+  ARTICLE,
+  ASIDE,
+  AUDIO,
+  B,
+  BDI,
+  BDO,
+  BLOCKQUOTE,
+  BODY,
+  BUTTON,
+  CANVAS,
+  CAPTION,
+  CITE,
+  CODE,
+  COLGROUP,
+  DATA,
+  DATALIST,
+  DD,
+  DEL,
+  DETAILS,
+  DFN,
+  DIALOG,
+  DIV,
+  DL,
+  DT,
+  EM,
+  FIELDSET,
+  FIGCAPTION,
+  FIGURE,
+  FOOTER,
+  FORM,
+  H1,
+  H2,
+  H3,
+  H4,
+  H5,
+  H6,
+  HEAD,
+  HEADER,
+  HGROUP,
+  HTML,
+  I,
+  IFRAME,
+  INS,
+  KBD,
+  LABEL,
+  LEGEND,
+  LI,
+  MAIN,
+  MAP,
+  MARK,
+  MATH,
+  MENU,
+  METER,
+  NAV,
+  NOSCRIPT,
+  OBJECT,
+  OL,
+  OPTGROUP,
+  OPTION,
+  OUTPUT,
+  P,
+  PICTURE,
+  PRE,
+  PROGRESS,
+  Q,
+  RB,
+  RP,
+  RT,
+  RTC,
+  RUBY,
+  S,
+  SAMP,
+  SCRIPT,
+  SECTION,
+  SELECT,
+  SLOT,
+  SMALL,
+  SPAN,
+  STRONG,
+  STYLE,
+  SUB,
+  SUMMARY,
+  SUP,
+  SVG,
+  TABLE,
+  TBODY,
+  TD,
+  TEMPLATE,
+  TEXTAREA,
+  TFOOT,
+  TH,
+  THEAD,
+  TIME,
+  TITLE,
+  TR,
+  U,
+  UL,
+  VAR,
+  VIDEO,
+
+  CUSTOM,
+};
+
+static const unordered_map<string, TagType> TAG_TYPES_BY_TAG_NAME = {
+  {"AREA", AREA},
+  {"BASE", BASE},
+  {"BASEFONT", BASEFONT},
+  {"BGSOUND", BGSOUND},
+  {"BR", BR},
+  {"COL", COL},
+  {"COMMAND", COMMAND},
+  {"EMBED", EMBED},
+  {"FRAME", FRAME},
+  {"HR", HR},
+  {"IMAGE", IMAGE},
+  {"IMG", IMG},
+  {"INPUT", INPUT},
+  {"ISINDEX", ISINDEX},
+  {"KEYGEN", KEYGEN},
+  {"LINK", LINK},
+  {"MENUITEM", MENUITEM},
+  {"META", META},
+  {"NEXTID", NEXTID},
+  {"PARAM", PARAM},
+  {"SOURCE", SOURCE},
+  {"TRACK", TRACK},
+  {"WBR", WBR},
+  {"A", A},
+  {"ABBR", ABBR},
+  {"ADDRESS", ADDRESS},
+  {"ARTICLE", ARTICLE},
+  {"ASIDE", ASIDE},
+  {"AUDIO", AUDIO},
+  {"B", B},
+  {"BDI", BDI},
+  {"BDO", BDO},
+  {"BLOCKQUOTE", BLOCKQUOTE},
+  {"BODY", BODY},
+  {"BUTTON", BUTTON},
+  {"CANVAS", CANVAS},
+  {"CAPTION", CAPTION},
+  {"CITE", CITE},
+  {"CODE", CODE},
+  {"COLGROUP", COLGROUP},
+  {"DATA", DATA},
+  {"DATALIST", DATALIST},
+  {"DD", DD},
+  {"DEL", DEL},
+  {"DETAILS", DETAILS},
+  {"DFN", DFN},
+  {"DIALOG", DIALOG},
+  {"DIV", DIV},
+  {"DL", DL},
+  {"DT", DT},
+  {"EM", EM},
+  {"FIELDSET", FIELDSET},
+  {"FIGCAPTION", FIGCAPTION},
+  {"FIGURE", FIGURE},
+  {"FOOTER", FOOTER},
+  {"FORM", FORM},
+  {"H1", H1},
+  {"H2", H2},
+  {"H3", H3},
+  {"H4", H4},
+  {"H5", H5},
+  {"H6", H6},
+  {"HEAD", HEAD},
+  {"HEADER", HEADER},
+  {"HGROUP", HGROUP},
+  {"HTML", HTML},
+  {"I", I},
+  {"IFRAME", IFRAME},
+  {"INS", INS},
+  {"KBD", KBD},
+  {"LABEL", LABEL},
+  {"LEGEND", LEGEND},
+  {"LI", LI},
+  {"MAIN", MAIN},
+  {"MAP", MAP},
+  {"MARK", MARK},
+  {"MATH", MATH},
+  {"MENU", MENU},
+  {"METER", METER},
+  {"NAV", NAV},
+  {"NOSCRIPT", NOSCRIPT},
+  {"OBJECT", OBJECT},
+  {"OL", OL},
+  {"OPTGROUP", OPTGROUP},
+  {"OPTION", OPTION},
+  {"OUTPUT", OUTPUT},
+  {"P", P},
+  {"PICTURE", PICTURE},
+  {"PRE", PRE},
+  {"PROGRESS", PROGRESS},
+  {"Q", Q},
+  {"RB", RB},
+  {"RP", RP},
+  {"RT", RT},
+  {"RTC", RTC},
+  {"RUBY", RUBY},
+  {"S", S},
+  {"SAMP", SAMP},
+  {"SCRIPT", SCRIPT},
+  {"SECTION", SECTION},
+  {"SELECT", SELECT},
+  {"SLOT", SLOT},
+  {"SMALL", SMALL},
+  {"SPAN", SPAN},
+  {"STRONG", STRONG},
+  {"STYLE", STYLE},
+  {"SUB", SUB},
+  {"SUMMARY", SUMMARY},
+  {"SUP", SUP},
+  {"SVG", SVG},
+  {"TABLE", TABLE},
+  {"TBODY", TBODY},
+  {"TD", TD},
+  {"TEMPLATE", TEMPLATE},
+  {"TEXTAREA", TEXTAREA},
+  {"TFOOT", TFOOT},
+  {"TH", TH},
+  {"THEAD", THEAD},
+  {"TIME", TIME},
+  {"TITLE", TITLE},
+  {"TR", TR},
+  {"U", U},
+  {"UL", UL},
+  {"VAR", VAR},
+  {"VIDEO", VIDEO},
+};
+
+struct Tag {
+  TagType type;
+  string custom_tag_name;
+
+  bool operator==(const Tag &other) const {
+    if (type != other.type) return false;
+    if (type == TagType::CUSTOM && custom_tag_name != other.custom_tag_name) return false;
+    return true;
+  }
+
+  inline bool is_void() const {
+    return type < END_OF_VOID_TAGS;
+  }
+
+  // string name() const {
+  //   return type == TagType::CUSTOM
+  //     ? custom_tag_name
+  //     : TAG_TYPES_BY_TAG_NAME.
+  // }
+
+  static Tag for_name(const string &name) {
+    auto type = TAG_TYPES_BY_TAG_NAME.find(name);
+    if (type != TAG_TYPES_BY_TAG_NAME.end()) {
+      return Tag { type->second, "" };
+    }
+
+    return Tag { CUSTOM, name };
+  }
+};

test.html

@@ -1 +1 @@
-<input value=stuff></input>
+<form><img src=something.png><br><input type=submit value=Ok /></form>