From 952767296dad8cdf157fed27b22e514de3ae37ad Mon Sep 17 00:00:00 2001
From: ownedbywuigi <ownedbywuigi@gmail.com>
Date: Sat, 25 Apr 2026 09:01:45 +0100
Subject: [PATCH] Issue #3057 - Implement new <select> HTML parser rules

---
 .../htmlparser/impl/ElementName.java          |   2 +-
 parser/html/nsHtml5ElementName.cpp            |   2 +-
 parser/html/nsHtml5TreeBuilder.cpp            | 112 ++++++++++++------
 .../htmlparser/tests/mochitest/mochitest.ini  |   1 +
 .../mochitest/test_select_parser_relaxed.html |  54 +++++++++
 5 files changed, 133 insertions(+), 38 deletions(-)
 create mode 100644 parser/htmlparser/tests/mochitest/test_select_parser_relaxed.html

diff --git a/parser/html/java/htmlparser/src/nu/validator/htmlparser/impl/ElementName.java b/parser/html/java/htmlparser/src/nu/validator/htmlparser/impl/ElementName.java
index 4b87d3fde2..4e5e482dae 100644
--- a/parser/html/java/htmlparser/src/nu/validator/htmlparser/impl/ElementName.java
+++ b/parser/html/java/htmlparser/src/nu/validator/htmlparser/impl/ElementName.java
@@ -2162,7 +2162,7 @@ public final class ElementName
     public static final ElementName SELECT = new ElementName("select", "select", 
     // CPPONLY: NS_NewHTMLSelectElement,
     // CPPONLY: NS_NewSVGUnknownElement, 
-    TreeBuilder.SELECT | SPECIAL);
+    TreeBuilder.SELECT | SPECIAL | SCOPING);
     public static final ElementName SCALARPRODUCT = new ElementName("scalarproduct", "scalarproduct", 
     // CPPONLY: NS_NewHTMLUnknownElement,
     // CPPONLY: NS_NewSVGUnknownElement, 
diff --git a/parser/html/nsHtml5ElementName.cpp b/parser/html/nsHtml5ElementName.cpp
index ecdfb102d4..4af8f7f289 100644
--- a/parser/html/nsHtml5ElementName.cpp
+++ b/parser/html/nsHtml5ElementName.cpp
@@ -866,7 +866,7 @@ nsHtml5ElementName::initializeStatics()
   ELT_RECT = new nsHtml5ElementName(nsHtml5Atoms::rect, nsHtml5Atoms::rect, NS_NewHTMLUnknownElement, NS_NewSVGRectElement, nsHtml5TreeBuilder::OTHER);
   ELT_RADIALGRADIENT = new nsHtml5ElementName(nsHtml5Atoms::radialgradient, nsHtml5Atoms::radialGradient, NS_NewHTMLUnknownElement, NS_NewSVGRadialGradientElement, nsHtml5TreeBuilder::OTHER);
   ELT_ROOT = new nsHtml5ElementName(nsHtml5Atoms::root, nsHtml5Atoms::root, NS_NewHTMLUnknownElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::OTHER);
-  ELT_SELECT = new nsHtml5ElementName(nsHtml5Atoms::select, nsHtml5Atoms::select, NS_NewHTMLSelectElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::SELECT | SPECIAL);
+  ELT_SELECT = new nsHtml5ElementName(nsHtml5Atoms::select, nsHtml5Atoms::select, NS_NewHTMLSelectElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::SELECT | SPECIAL | SCOPING);
   ELT_SCALARPRODUCT = new nsHtml5ElementName(nsHtml5Atoms::scalarproduct, nsHtml5Atoms::scalarproduct, NS_NewHTMLUnknownElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::OTHER);
   ELT_SUBSET = new nsHtml5ElementName(nsHtml5Atoms::subset, nsHtml5Atoms::subset, NS_NewHTMLUnknownElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::OTHER);
   ELT_SLOT = new nsHtml5ElementName(nsHtml5Atoms::slot, nsHtml5Atoms::slot, NS_NewHTMLSlotElement, NS_NewSVGUnknownElement, nsHtml5TreeBuilder::OTHER);
diff --git a/parser/html/nsHtml5TreeBuilder.cpp b/parser/html/nsHtml5TreeBuilder.cpp
index 76a2398f52..e7f6b591af 100644
--- a/parser/html/nsHtml5TreeBuilder.cpp
+++ b/parser/html/nsHtml5TreeBuilder.cpp
@@ -1216,6 +1216,14 @@ nsHtml5TreeBuilder::startTag(nsHtml5ElementName* elementName, nsHtml5HtmlAttribu
             }
             case HR: {
               implicitlyCloseP();
+              if (findLastInScope(nsHtml5Atoms::select) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                generateImpliedEndTags();
+                if (!!MOZ_UNLIKELY(mViewSource) &&
+                    (findLastInScope(nsHtml5Atoms::option) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK ||
+                     findLastInScope(nsHtml5Atoms::optgroup) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK)) {
+                  errUnclosedElements(currentPtr, name);
+                }
+              }
               appendVoidElementToCurrentMayFoster(elementName, attributes);
               selfClosing = false;
               attributes = nullptr;
@@ -1229,6 +1237,19 @@ nsHtml5TreeBuilder::startTag(nsHtml5ElementName* elementName, nsHtml5HtmlAttribu
             case IMG:
             case KEYGEN:
             case INPUT: {
+              if (fragment && nsHtml5Atoms::select == contextName) {
+                errStartTagWithSelectOpen(name);
+                NS_HTML5_BREAK(starttagloop);
+              }
+              eltPos = findLastInScope(nsHtml5Atoms::select);
+              if (eltPos != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                errStartTagWithSelectOpen(name);
+                while (currentPtr >= eltPos) {
+                  pop();
+                }
+                resetTheInsertionMode();
+                NS_HTML5_CONTINUE(starttagloop);
+              }
               reconstructTheActiveFormattingElements();
               appendVoidElementToCurrentMayFoster(elementName, attributes, formPointer);
               selfClosing = false;
@@ -1313,33 +1334,54 @@ nsHtml5TreeBuilder::startTag(nsHtml5ElementName* elementName, nsHtml5HtmlAttribu
               NS_HTML5_BREAK(starttagloop);
             }
             case SELECT: {
+              if (fragment && nsHtml5Atoms::select == contextName) {
+                errStartSelectWhereEndSelectExpected();
+                NS_HTML5_BREAK(starttagloop);
+              }
+              eltPos = findLastInScope(nsHtml5Atoms::select);
+              if (eltPos != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                errStartSelectWhereEndSelectExpected();
+                while (currentPtr >= eltPos) {
+                  pop();
+                }
+                NS_HTML5_BREAK(starttagloop);
+              }
               reconstructTheActiveFormattingElements();
               appendToCurrentNodeAndPushElementMayFoster(elementName, attributes, formPointer);
-              switch(mode) {
-                case IN_TABLE:
-                case IN_CAPTION:
-                case IN_COLUMN_GROUP:
-                case IN_TABLE_BODY:
-                case IN_ROW:
-                case IN_CELL: {
-                  mode = IN_SELECT_IN_TABLE;
-                  break;
-                }
-                default: {
-                  mode = IN_SELECT;
-                  break;
-                }
-              }
+              framesetOk = false;
               attributes = nullptr;
               NS_HTML5_BREAK(starttagloop);
             }
-            case OPTGROUP:
             case OPTION: {
-              if (isCurrent(nsHtml5Atoms::option)) {
+              if (findLastInScope(nsHtml5Atoms::select) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                generateImpliedEndTagsExceptFor(nsHtml5Atoms::optgroup);
+                eltPos = findLastInScope(nsHtml5Atoms::option);
+                if (!!MOZ_UNLIKELY(mViewSource) && eltPos != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                  errUnclosedElements(eltPos, name);
+                }
+              } else {
+                if (isCurrent(nsHtml5Atoms::option)) {
+                  pop();
+                }
+              }
+              reconstructTheActiveFormattingElements();
+              appendToCurrentNodeAndPushElement(elementName, attributes);
+              attributes = nullptr;
+              NS_HTML5_BREAK(starttagloop);
+            }
+            case OPTGROUP: {
+              if (findLastInScope(nsHtml5Atoms::select) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+                generateImpliedEndTags();
+                if (!!MOZ_UNLIKELY(mViewSource) &&
+                    (findLastInScope(nsHtml5Atoms::option) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK ||
+                     findLastInScope(nsHtml5Atoms::optgroup) != nsHtml5TreeBuilder::NOT_FOUND_ON_STACK)) {
+                  errUnclosedElements(currentPtr, name);
+                }
+              } else if (isCurrent(nsHtml5Atoms::option)) {
                 pop();
               }
               reconstructTheActiveFormattingElements();
-              appendToCurrentNodeAndPushElementMayFoster(elementName, attributes);
+              appendToCurrentNodeAndPushElement(elementName, attributes);
               attributes = nullptr;
               NS_HTML5_BREAK(starttagloop);
             }
@@ -2697,6 +2739,21 @@ nsHtml5TreeBuilder::endTag(nsHtml5ElementName* elementName)
           case TEMPLATE: {
             break;
           }
+          case SELECT: {
+            eltPos = findLastInScope(name);
+            if (eltPos == nsHtml5TreeBuilder::NOT_FOUND_ON_STACK) {
+              errStrayEndTag(name);
+            } else {
+              generateImpliedEndTags();
+              if (!!MOZ_UNLIKELY(mViewSource) && !isCurrent(name)) {
+                errUnclosedElements(eltPos, name);
+              }
+              while (currentPtr >= eltPos) {
+                pop();
+              }
+            }
+            NS_HTML5_BREAK(endtagloop);
+          }
           case AREA_OR_WBR:
 #ifdef ENABLE_VOID_MENUITEM
           case MENUITEM:
@@ -2712,7 +2769,6 @@ nsHtml5TreeBuilder::endTag(nsHtml5ElementName* elementName)
           case IFRAME:
           case NOEMBED:
           case NOFRAMES:
-          case SELECT:
           case TABLE:
           case TEXTAREA: {
             errStrayEndTag(name);
@@ -3335,23 +3391,7 @@ nsHtml5TreeBuilder::resetTheInsertionMode()
         return;
       }
     }
-    if (nsHtml5Atoms::select == name) {
-      int32_t ancestorIndex = i;
-      while (ancestorIndex > 0) {
-        nsHtml5StackNode* ancestor = stack[ancestorIndex--];
-        if (kNameSpaceID_XHTML == ancestor->ns) {
-          if (nsHtml5Atoms::template_ == ancestor->name) {
-            break;
-          }
-          if (nsHtml5Atoms::table == ancestor->name) {
-            mode = IN_SELECT_IN_TABLE;
-            return;
-          }
-        }
-      }
-      mode = IN_SELECT;
-      return;
-    } else if (nsHtml5Atoms::td == name || nsHtml5Atoms::th == name) {
+    if (nsHtml5Atoms::td == name || nsHtml5Atoms::th == name) {
       mode = IN_CELL;
       return;
     } else if (nsHtml5Atoms::tr == name) {
diff --git a/parser/htmlparser/tests/mochitest/mochitest.ini b/parser/htmlparser/tests/mochitest/mochitest.ini
index dcb30d6e80..0d089e9b02 100644
--- a/parser/htmlparser/tests/mochitest/mochitest.ini
+++ b/parser/htmlparser/tests/mochitest/mochitest.ini
@@ -147,3 +147,4 @@ skip-if = toolkit == 'android' #TIMED_OUT
 # Disable test due to frequent orange on Mac
 #		test_bug534293.html
 [test_bug1209658.html]
+[test_select_parser_relaxed.html]
diff --git a/parser/htmlparser/tests/mochitest/test_select_parser_relaxed.html b/parser/htmlparser/tests/mochitest/test_select_parser_relaxed.html
new file mode 100644
index 0000000000..d78947dc5b
--- /dev/null
+++ b/parser/htmlparser/tests/mochitest/test_select_parser_relaxed.html
@@ -0,0 +1,54 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1933591
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for relaxed select parser rules</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+SimpleTest.waitForExplicitFinish();
+
+function parse(markup) {
+  const host = document.createElement("div");
+  host.innerHTML = markup;
+  return host;
+}
+
+(function testDivAllowedInSelect() {
+  const host = parse("<select><div><option>One</option></div></select>");
+  const select = host.querySelector("select");
+  ok(!!select, "select should parse");
+  is(select.firstElementChild && select.firstElementChild.tagName, "DIV",
+     "div should remain inside select");
+  is(select.querySelector("option").textContent, "One",
+     "option should still be found under nested content");
+})();
+
+(function testTextareaDoesNotCloseSelect() {
+  const host = parse("<select><textarea>abc</textarea><option>One</option></select>");
+  const select = host.querySelector("select");
+  ok(!!select, "select should parse");
+  ok(!!select.querySelector("textarea"), "textarea should remain inside select");
+  ok(!!select.querySelector("option"), "option should remain inside select");
+})();
+
+(function testInputStillClosesSelect() {
+  const host = parse("<select><div><input></div><option>One</option></select>");
+  const select = host.querySelector("select");
+  ok(!!select, "select should parse");
+  ok(!select.querySelector("input"), "input should not remain inside select");
+  ok(!select.querySelector("option"), "option should no longer be inside the closed select");
+  ok(!!host.querySelector("input"), "input should still be inserted in the tree");
+})();
+
+SimpleTest.finish();
+</script>
+</pre>
+</body>
+</html>