From 5419a9477fa54297ed5e02b3769374e07e0921f3 Mon Sep 17 00:00:00 2001
From: Anders Kaseorg <andersk@mit.edu>
Date: Fri, 19 Apr 2024 05:52:16 -0700
Subject: [PATCH] =?UTF-8?q?fix(html/codegen):=20Expand=20elements=20before?=
 =?UTF-8?q?=20which=20body=20isn=E2=80=99t=20elided=20(#8877)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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**Description:**

For example, transforming `<body><noscript>` to `<noscript>` would
incorrectly change the meaning so `<noscript>` is parsed as a child of
`<head>`.

Reference: [§13.2.6.4.4 The "in head" insertion
mode](https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-inhead),
[13.2.6.4.6 The "after head" insertion
mode](https://html.spec.whatwg.org/multipage/parsing.html#the-after-head-insertion-mode).

**Related issue:**

- Closes #8876.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
---
 crates/swc_html_codegen/src/lib.rs                 | 14 ++++++++------
 .../tests/fixture/body-noscript/input.html         |  8 ++++++++
 .../tests/fixture/body-noscript/output.html        |  9 +++++++++
 .../tests/fixture/body-noscript/output.min.html    |  6 ++++++
 .../tests/fixture/text/noscript/output.min.html    |  2 +-
 5 files changed, 32 insertions(+), 7 deletions(-)
 create mode 100644 crates/swc_html_codegen/tests/fixture/body-noscript/input.html
 create mode 100644 crates/swc_html_codegen/tests/fixture/body-noscript/output.html
 create mode 100644 crates/swc_html_codegen/tests/fixture/body-noscript/output.min.html
diff --git a/crates/swc_html_codegen/src/lib.rs b/crates/swc_html_codegen/src/lib.rs
index aecbad102a30..b13fd2f83d70 100644
--- a/crates/swc_html_codegen/src/lib.rs
+++ b/crates/swc_html_codegen/src/lib.rs
@@ -234,8 +234,7 @@ where
                 }
                 // A body element's start tag can be omitted if the element is empty, or if the
                 // first thing inside the body element is not ASCII whitespace or a comment, except
-                // if the first thing inside the body element is a meta, link, script, style, or
-                // template element.
+                // if the first thing inside the body element would be parsed differently outside.
                 "body"
                     if n.children.is_empty()
                         || (match n.children.first() {
@@ -253,14 +252,17 @@ where
                             })) if *namespace == Namespace::HTML
                                 && matches!(
                                     &**tag_name,
-                                    "meta"
+                                    "base"
+                                        | "basefont"
+                                        | "bgsound"
+                                        | "frameset"
                                         | "link"
+                                        | "meta"
+                                        | "noframes"
+                                        | "noscript"
                                         | "script"
                                         | "style"
                                         | "template"
-                                        | "bgsound"
-                                        | "basefont"
-                                        | "base"
                                         | "title"
                                 ) =>
                             {
diff --git a/crates/swc_html_codegen/tests/fixture/body-noscript/input.html b/crates/swc_html_codegen/tests/fixture/body-noscript/input.html
new file mode 100644
index 000000000000..574c19c06a49
--- /dev/null
+++ b/crates/swc_html_codegen/tests/fixture/body-noscript/input.html
@@ -0,0 +1,8 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <title>Test</title>
+  </head>
+  <body><noscript>This app requires JavaScript.</noscript></body>
+</html>
diff --git a/crates/swc_html_codegen/tests/fixture/body-noscript/output.html b/crates/swc_html_codegen/tests/fixture/body-noscript/output.html
new file mode 100644
index 000000000000..791a10c915aa
--- /dev/null
+++ b/crates/swc_html_codegen/tests/fixture/body-noscript/output.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="utf-8" />
+    <title>Test</title>
+  </head>
+  <body><noscript>This app requires JavaScript.</noscript>
+
+</body></html>
\ No newline at end of file
diff --git a/crates/swc_html_codegen/tests/fixture/body-noscript/output.min.html b/crates/swc_html_codegen/tests/fixture/body-noscript/output.min.html
new file mode 100644
index 000000000000..16ffc89fe005
--- /dev/null
+++ b/crates/swc_html_codegen/tests/fixture/body-noscript/output.min.html
@@ -0,0 +1,6 @@
+<!doctype html><html lang=en><head>
+    <meta charset=utf-8>
+    <title>Test</title>
+  </head>
+  <body><noscript>This app requires JavaScript.</noscript>
+
diff --git a/crates/swc_html_minifier/tests/fixture/text/noscript/output.min.html b/crates/swc_html_minifier/tests/fixture/text/noscript/output.min.html
index 93f5f479bebd..b539907e7b6b 100644
--- a/crates/swc_html_minifier/tests/fixture/text/noscript/output.min.html
+++ b/crates/swc_html_minifier/tests/fixture/text/noscript/output.min.html
@@ -1,4 +1,4 @@
-<!doctype html><html lang=en><meta charset=UTF-8><meta name=viewport content="width=device-width,user-scalable=no,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0"><meta http-equiv=X-UA-Compatible content="ie=edge"><title>Document</title><noscript>
+<!doctype html><html lang=en><meta charset=UTF-8><meta name=viewport content="width=device-width,user-scalable=no,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0"><meta http-equiv=X-UA-Compatible content="ie=edge"><title>Document</title><body><noscript>
     
     <a href=https://www.mozilla.com/>External Link</a>
 </noscript>
