From 2529b928181d4b0c47518fbcbc307c3c8e51dbc9 Mon Sep 17 00:00:00 2001
From: Konv Suu <hi@kovsu.com>
Date: Sat, 12 Sep 2026 20:31:10 +0800
Subject: [PATCH] Format `<script>` content in glimmer templates (#20012)

Co-authored-by: fisker <lionkay@gmail.com>
---
 changelog_unreleased/handlebars/20012.md      |  21 ++
 src/language-handlebars/embed.js              |  65 +++++--
 src/language-handlebars/massage-ast/index.js  |   9 +-
 src/language-handlebars/printer-glimmer.js    |  16 +-
 src/language-handlebars/utilities.js          |   8 +-
 .../__snapshots__/format.test.js.snap         | 181 ++++++++++++++++++
 .../__snapshots__/format.test.js.snap         |  16 ++
 .../format.test.js                            |   1 +
 .../embedded-language-formatting-off/test.hbs |   3 +
 .../handlebars/script-tag/format.test.js      |   1 +
 .../handlebars/script-tag/script-tag.hbs      |  31 +++
 .../handlebars/script-tag/type-attribute.hbs  |  21 ++
 .../handlebars/script-tag/with-mustache.hbs   |   8 +
 .../format/handlebars/script-tag/with-src.hbs |   4 +
 14 files changed, 357 insertions(+), 28 deletions(-)
 create mode 100644 changelog_unreleased/handlebars/20012.md
 create mode 100644 tests/format/handlebars/script-tag/__snapshots__/format.test.js.snap
 create mode 100644 tests/format/handlebars/script-tag/embedded-language-formatting-off/__snapshots__/format.test.js.snap
 create mode 100644 tests/format/handlebars/script-tag/embedded-language-formatting-off/format.test.js
 create mode 100644 tests/format/handlebars/script-tag/embedded-language-formatting-off/test.hbs
 create mode 100644 tests/format/handlebars/script-tag/format.test.js
 create mode 100644 tests/format/handlebars/script-tag/script-tag.hbs
 create mode 100644 tests/format/handlebars/script-tag/type-attribute.hbs
 create mode 100644 tests/format/handlebars/script-tag/with-mustache.hbs
 create mode 100644 tests/format/handlebars/script-tag/with-src.hbs

diff --git a/changelog_unreleased/handlebars/20012.md b/changelog_unreleased/handlebars/20012.md
new file mode 100644
index 000000000..67a0176f7
--- /dev/null
+++ b/changelog_unreleased/handlebars/20012.md
@@ -0,0 +1,21 @@
+#### Support embedded `<script>` (#20012 by @kovsu)
+
+<!-- prettier-ignore -->
+```hbs
+{{! Input }}
+<script>
+  const a =    1;
+  console.log( a );
+</script>
+
+{{! Prettier stable }}
+<script>
+  const a = 1; console.log( a );
+</script>
+
+{{! Prettier main }}
+<script>
+  const a = 1;
+  console.log(a);
+</script>
+```
diff --git a/src/language-handlebars/embed.js b/src/language-handlebars/embed.js
index ff41c0beb..4d46e2cab 100644
--- a/src/language-handlebars/embed.js
+++ b/src/language-handlebars/embed.js
@@ -1,4 +1,40 @@
-import { isPlainTextStyleElement } from "./utilities.js";
+import { isPlainTextStyleOrScriptElement } from "./utilities.js";
+
+function getAttribute(node, name) {
+  return node.attributes.find(
+    (attribute) => attribute.type === "AttrNode" && attribute.name === name,
+  );
+}
+
+function getTextValue(attribute) {
+  return attribute.value.type === "TextNode"
+    ? attribute.value.chars
+    : undefined;
+}
+
+function getScriptTextToDocOptions(node) {
+  if (getAttribute(node, "src")) {
+    return;
+  }
+
+  const typeAttribute = getAttribute(node, "type");
+  const type = typeAttribute ? getTextValue(typeAttribute) : undefined;
+
+  if (!typeAttribute || type === "module" || type === "text/javascript") {
+    return {
+      parser: "babel",
+      __embeddedInHtml: true,
+      __babelSourceType: type === "module" ? "module" : "script",
+    };
+  }
+}
+
+function getStyleTextToDocOptions(node) {
+  const langAttribute = getAttribute(node, "lang");
+  if (!langAttribute || getTextValue(langAttribute) === "css") {
+    return { parser: "css" };
+  }
+}
 
 function embed(path /* , options*/) {
   const { node } = path;
@@ -9,30 +45,27 @@ function embed(path /* , options*/) {
 
   const { parent } = path;
 
-  if (!(isPlainTextStyleElement(parent) && parent.children[0] === node)) {
+  if (!(
+    isPlainTextStyleOrScriptElement(parent) && parent.children[0] === node
+  )) {
     return;
   }
 
-  const languageAttribute = parent.attributes.find(
-    (attribute) => attribute.type === "AttrNode" && attribute.name === "lang",
-  );
-  if (
-    languageAttribute &&
-    !(
-      languageAttribute.value.type === "TextNode" &&
-      languageAttribute.value.chars === "css"
-    )
-  ) {
+  const textToDocOptions =
+    parent.tag === "style"
+      ? getStyleTextToDocOptions(parent)
+      : getScriptTextToDocOptions(parent);
+
+  if (!textToDocOptions) {
     return;
   }
 
   return async (textToDoc) => {
-    const context = node.chars;
-    if (!context.trim()) {
+    const content = node.chars;
+    if (!content.trim()) {
       return "";
     }
-    const doc = await textToDoc(context, { parser: "css" });
-    return doc;
+    return await textToDoc(content, textToDocOptions);
   };
 }
 
diff --git a/src/language-handlebars/massage-ast/index.js b/src/language-handlebars/massage-ast/index.js
index 894e17dc9..226439819 100644
--- a/src/language-handlebars/massage-ast/index.js
+++ b/src/language-handlebars/massage-ast/index.js
@@ -1,5 +1,5 @@
 import htmlWhitespace from "../../utilities/html-whitespace.js";
-import { isPlainTextStyleElement } from "../utilities.js";
+import { isPlainTextStyleOrScriptElement } from "../utilities.js";
 
 function massageAstNode(original, cloned, parent) {
   // (Glimmer/HTML) ignore TextNode
@@ -9,8 +9,11 @@ function massageAstNode(original, cloned, parent) {
       return null;
     }
 
-    // CSS will be formatted
-    if (isPlainTextStyleElement(parent) && parent.children[0] === original) {
+    // CSS/JS will be formatted
+    if (
+      isPlainTextStyleOrScriptElement(parent) &&
+      parent.children[0] === original
+    ) {
       cloned.chars = "";
     } else {
       cloned.chars = htmlWhitespace.split(trimmed).join(" ");
diff --git a/src/language-handlebars/printer-glimmer.js b/src/language-handlebars/printer-glimmer.js
index bda72ee3c..f771f50ab 100644
--- a/src/language-handlebars/printer-glimmer.js
+++ b/src/language-handlebars/printer-glimmer.js
@@ -20,7 +20,7 @@ import { locEnd, locStart } from "./loc.js";
 import { massageAstNode } from "./massage-ast/index.js";
 import {
   hasPrettierIgnore,
-  isPlainTextStyleElement,
+  isPlainTextStyleOrScriptElement,
   isVoidElement,
   isWhitespaceNode,
 } from "./utilities.js";
@@ -60,11 +60,11 @@ function print(path, options, print) {
       }
 
       const endingTag = ["</", node.tag, ">"];
-      const isPlainStyle = isPlainTextStyleElement(node);
+      const isPlainStyleOrScript = isPlainTextStyleOrScriptElement(node);
 
       if (
         node.children.length === 0 ||
-        ((!isWhitespaceSensitive || isPlainStyle) &&
+        ((!isWhitespaceSensitive || isPlainStyleOrScript) &&
           node.children.every((node) => isWhitespaceNode(node)))
       ) {
         return [startingTag, endingTag];
@@ -72,7 +72,7 @@ function print(path, options, print) {
 
       const parts = path.map(print, "children");
 
-      if (isPlainStyle || !isWhitespaceSensitive) {
+      if (!isWhitespaceSensitive || isPlainStyleOrScript) {
         return [startingTag, indent([softline, ...parts]), softline, endingTag];
       }
 
@@ -163,7 +163,8 @@ function print(path, options, print) {
     case "TextNode": {
       // Don't format content:
       // 1. in `<pre>`,
-      // 2. in `<style>`
+      // 2. in `<style>`,
+      // 3. in `<script>`
 
       let text = node.chars;
 
@@ -173,7 +174,10 @@ function print(path, options, print) {
           return replaceEndOfLine(text);
         }
 
-        if (isPlainTextStyleElement(parent)) {
+        if (
+          isPlainTextStyleOrScriptElement(parent) &&
+          parent.children[0] === node
+        ) {
           text = text.replaceAll(/^\n+/g, "");
           text = htmlWhitespace.trimEnd(text);
           text = htmlWhitespace.dedentString(text);
diff --git a/src/language-handlebars/utilities.js b/src/language-handlebars/utilities.js
index fd9c6c796..c1eea8eba 100644
--- a/src/language-handlebars/utilities.js
+++ b/src/language-handlebars/utilities.js
@@ -42,8 +42,10 @@ function isPlainTextElement(node) {
   );
 }
 
-function isPlainTextStyleElement(node) {
-  return isPlainTextElement(node) && node.tag === "style";
+function isPlainTextStyleOrScriptElement(node) {
+  return (
+    isPlainTextElement(node) && (node.tag === "style" || node.tag === "script")
+  );
 }
 
 function isPrettierIgnoreNode(node) {
@@ -67,7 +69,7 @@ function hasPrettierIgnore(path) {
 
 export {
   hasPrettierIgnore,
-  isPlainTextStyleElement,
+  isPlainTextStyleOrScriptElement,
   isVoidElement,
   isWhitespaceNode,
 };
diff --git a/tests/format/handlebars/script-tag/__snapshots__/format.test.js.snap b/tests/format/handlebars/script-tag/__snapshots__/format.test.js.snap
new file mode 100644
index 000000000..c2783a77f
--- /dev/null
+++ b/tests/format/handlebars/script-tag/__snapshots__/format.test.js.snap
@@ -0,0 +1,181 @@
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
+
+exports[`script-tag.hbs format 1`] = `
+====================================options=====================================
+parsers: ["glimmer"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+<script></script>
+
+<script>   </script>
+
+<script type="module">
+  import    a   from   "a"   ;
+</script>
+
+<script>
+  // Should not support TLA in script without \`[type="module"]\`
+  await shouldNotFormat   (   a   );
+</script>
+<script type="module">
+  // TLA
+  await shouldFormat   (   a   );
+</script>
+
+<script type="module">
+<!--Should not support HTML comment in \`script[type="module"]\`
+  shouldNotFormat   (   a   );
+-->
+</script>
+<script>
+<!--html comment
+  shouldFormat   (   a   );
+-->
+</script>
+
+<script>
+  const template = html\`<div><script>shouldFormat   (   )<\\/script></div>\`;
+</script>
+
+=====================================output=====================================
+<script></script>
+
+<script></script>
+
+<script type="module">
+  import a from "a";
+</script>
+
+<script>
+  // Should not support TLA in script without \`[type="module"]\`
+  await shouldNotFormat   (   a   );
+</script>
+<script type="module">
+  // TLA
+  await shouldFormat(a);
+</script>
+
+<script type="module">
+  <!--Should not support HTML comment in \`script[type="module"]\`
+    shouldNotFormat   (   a   );
+  -->
+</script>
+<script>
+  <!--html comment
+  shouldFormat(a);
+  -->
+</script>
+
+<script>
+  const template = html\`<div>
+    <script>
+      shouldFormat();
+    <\\/script>
+  </div>\`;
+</script>
+================================================================================
+`;
+
+exports[`type-attribute.hbs format 1`] = `
+====================================options=====================================
+parsers: ["glimmer"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+<script>
+   shouldFormat   (   );
+</script>
+
+<script type="text/javascript">
+   shouldFormat   (   );
+</script>
+
+<script type>
+   shouldNotFormat   (   );
+</script>
+<script type="">
+   shouldNotFormat   (   );
+</script>
+<script type="unknown">
+   shouldNotFormat   (   );
+</script>
+
+<script type="application/ld+json">
+  {   "should"   :   "not format" }
+</script>
+
+=====================================output=====================================
+<script>
+  shouldFormat();
+</script>
+
+<script type="text/javascript">
+  shouldFormat();
+</script>
+
+<script type>
+  shouldNotFormat   (   );
+</script>
+<script type="">
+  shouldNotFormat   (   );
+</script>
+<script type="unknown">
+  shouldNotFormat   (   );
+</script>
+
+<script type="application/ld+json">
+  {   "should"   :   "not format" }
+</script>
+================================================================================
+`;
+
+exports[`with-mustache.hbs format 1`] = `
+====================================options=====================================
+parsers: ["glimmer"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+<script>
+  shouldNotFormat(   {{foo}} )
+</script>
+<script>
+  shouldNotFormat(   '{{user.name}}' )
+  {{#if debug}}shouldNotFormat(   'debug' ){{/if}}
+</script>
+<script>{{foo}}</script>
+
+=====================================output=====================================
+<script>
+  shouldNotFormat(
+  {{foo}}
+  )
+</script>
+<script>
+  shouldNotFormat( '{{user.name}}' )
+  {{#if debug}}shouldNotFormat( 'debug' ){{/if}}
+</script>
+<script>{{foo}}</script>
+================================================================================
+`;
+
+exports[`with-src.hbs format 1`] = `
+====================================options=====================================
+parsers: ["glimmer"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+<script src="main.js"></script>
+<script src="main.js">shouldNotFormat   (      );</script>
+<script src>shouldNotFormat   (      );</script>
+<script src="">shouldNotFormat   (      );</script>
+
+=====================================output=====================================
+<script src="main.js"></script>
+<script src="main.js">
+  shouldNotFormat   (      );
+</script>
+<script src>
+  shouldNotFormat   (      );
+</script>
+<script src="">
+  shouldNotFormat   (      );
+</script>
+================================================================================
+`;
diff --git a/tests/format/handlebars/script-tag/embedded-language-formatting-off/__snapshots__/format.test.js.snap b/tests/format/handlebars/script-tag/embedded-language-formatting-off/__snapshots__/format.test.js.snap
new file mode 100644
index 000000000..e90abf958
--- /dev/null
+++ b/tests/format/handlebars/script-tag/embedded-language-formatting-off/__snapshots__/format.test.js.snap
@@ -0,0 +1,16 @@
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
+
+exports[`test.hbs - {"embeddedLanguageFormatting":"off"} format 1`] = `
+====================================options=====================================
+embeddedLanguageFormatting: "off"
+parsers: ["glimmer"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+<script>
+   call   (   );
+</script>
+
+=====================================output=====================================
+<script>call   (   );</script>
+================================================================================
+`;
diff --git a/tests/format/handlebars/script-tag/embedded-language-formatting-off/format.test.js b/tests/format/handlebars/script-tag/embedded-language-formatting-off/format.test.js
new file mode 100644
index 000000000..a2d3c8dee
--- /dev/null
+++ b/tests/format/handlebars/script-tag/embedded-language-formatting-off/format.test.js
@@ -0,0 +1 @@
+runFormatTest(import.meta, ["glimmer"], { embeddedLanguageFormatting: "off" });
diff --git a/tests/format/handlebars/script-tag/embedded-language-formatting-off/test.hbs b/tests/format/handlebars/script-tag/embedded-language-formatting-off/test.hbs
new file mode 100644
index 000000000..7c3c52973
--- /dev/null
+++ b/tests/format/handlebars/script-tag/embedded-language-formatting-off/test.hbs
@@ -0,0 +1,3 @@
+<script>
+   call   (   );
+</script>
diff --git a/tests/format/handlebars/script-tag/format.test.js b/tests/format/handlebars/script-tag/format.test.js
new file mode 100644
index 000000000..2dbcbb457
--- /dev/null
+++ b/tests/format/handlebars/script-tag/format.test.js
@@ -0,0 +1 @@
+runFormatTest(import.meta, ["glimmer"]);
diff --git a/tests/format/handlebars/script-tag/script-tag.hbs b/tests/format/handlebars/script-tag/script-tag.hbs
new file mode 100644
index 000000000..d1697a4e3
--- /dev/null
+++ b/tests/format/handlebars/script-tag/script-tag.hbs
@@ -0,0 +1,31 @@
+<script></script>
+
+<script>   </script>
+
+<script type="module">
+  import    a   from   "a"   ;
+</script>
+
+<script>
+  // Should not support TLA in script without `[type="module"]`
+  await shouldNotFormat   (   a   );
+</script>
+<script type="module">
+  // TLA
+  await shouldFormat   (   a   );
+</script>
+
+<script type="module">
+<!--Should not support HTML comment in `script[type="module"]`
+  shouldNotFormat   (   a   );
+-->
+</script>
+<script>
+<!--html comment
+  shouldFormat   (   a   );
+-->
+</script>
+
+<script>
+  const template = html`<div><script>shouldFormat   (   )<\/script></div>`;
+</script>
diff --git a/tests/format/handlebars/script-tag/type-attribute.hbs b/tests/format/handlebars/script-tag/type-attribute.hbs
new file mode 100644
index 000000000..4363987cc
--- /dev/null
+++ b/tests/format/handlebars/script-tag/type-attribute.hbs
@@ -0,0 +1,21 @@
+<script>
+   shouldFormat   (   );
+</script>
+
+<script type="text/javascript">
+   shouldFormat   (   );
+</script>
+
+<script type>
+   shouldNotFormat   (   );
+</script>
+<script type="">
+   shouldNotFormat   (   );
+</script>
+<script type="unknown">
+   shouldNotFormat   (   );
+</script>
+
+<script type="application/ld+json">
+  {   "should"   :   "not format" }
+</script>
diff --git a/tests/format/handlebars/script-tag/with-mustache.hbs b/tests/format/handlebars/script-tag/with-mustache.hbs
new file mode 100644
index 000000000..73ef0a888
--- /dev/null
+++ b/tests/format/handlebars/script-tag/with-mustache.hbs
@@ -0,0 +1,8 @@
+<script>
+  shouldNotFormat(   {{foo}} )
+</script>
+<script>
+  shouldNotFormat(   '{{user.name}}' )
+  {{#if debug}}shouldNotFormat(   'debug' ){{/if}}
+</script>
+<script>{{foo}}</script>
diff --git a/tests/format/handlebars/script-tag/with-src.hbs b/tests/format/handlebars/script-tag/with-src.hbs
new file mode 100644
index 000000000..c9cb0c406
--- /dev/null
+++ b/tests/format/handlebars/script-tag/with-src.hbs
@@ -0,0 +1,4 @@
+<script src="main.js"></script>
+<script src="main.js">shouldNotFormat   (      );</script>
+<script src>shouldNotFormat   (      );</script>
+<script src="">shouldNotFormat   (      );</script>