From d452be5cb0d30ac68aa15401fdfff4816ead0573 Mon Sep 17 00:00:00 2001
From: fisker Cheung <lionkay@gmail.com>
Date: Mon, 27 Oct 2025 08:46:30 +0800
Subject: [PATCH] Don't force handlebars elements to break in
 `htmlWhitespaceSensitivity: "ignore"` mode (#18133)

---
 changelog_unreleased/handlebars/18133.md      | 14 +++++
 src/language-handlebars/printer-glimmer.js    | 62 ++++++-------------
 .../__snapshots__/format.test.js.snap         |  9 +--
 3 files changed, 37 insertions(+), 48 deletions(-)
 create mode 100644 changelog_unreleased/handlebars/18133.md

diff --git a/changelog_unreleased/handlebars/18133.md b/changelog_unreleased/handlebars/18133.md
new file mode 100644
index 000000000..943cbdc12
--- /dev/null
+++ b/changelog_unreleased/handlebars/18133.md
@@ -0,0 +1,14 @@
+#### Don't force elements to break with `--html-whitespace-sensitivity=ignore` (#18133 by @fisker)
+
+<!-- prettier-ignore -->
+```hbs
+{{! Input }}
+<div> </div>
+
+{{! Prettier stable (--html-whitespace-ensitivity=ignore) }}
+<div>
+</div>
+
+{{! Prettier main (--html-whitespace-ensitivity=ignore) }}
+<div></div>
+```
diff --git a/src/language-handlebars/printer-glimmer.js b/src/language-handlebars/printer-glimmer.js
index 4c5a94365..073c54c01 100644
--- a/src/language-handlebars/printer-glimmer.js
+++ b/src/language-handlebars/printer-glimmer.js
@@ -40,40 +40,36 @@ function print(path, options, print) {
       return group(path.map(print, "body"));
 
     case "ElementNode": {
-      const startingTag = group(printStartingTag(path, print));
+      const isWhitespaceSensitive =
+        options.htmlWhitespaceSensitivity !== "ignore";
 
-      const escapeNextElementNode =
-        options.htmlWhitespaceSensitivity === "ignore" &&
-        path.next?.type === "ElementNode"
+      const startingTag = [
+        !isWhitespaceSensitive && path.previous?.type === "ElementNode"
           ? softline
-          : "";
+          : "",
+        group([printStartingTag(path, print)]),
+      ];
 
       if (isVoidElement(node)) {
-        return [startingTag, escapeNextElementNode];
+        return [startingTag];
       }
 
       const endingTag = ["</", node.tag, ">"];
 
-      if (node.children.length === 0) {
-        return [startingTag, indent(endingTag), escapeNextElementNode];
+      if (
+        node.children.length === 0 ||
+        (!isWhitespaceSensitive &&
+          node.children.every((node) => isWhitespaceNode(node)))
+      ) {
+        return [startingTag, endingTag];
+      }
+      const parts = path.map(print, "children");
+
+      if (!isWhitespaceSensitive) {
+        return [startingTag, indent([softline, ...parts]), softline, endingTag];
       }
 
-      if (options.htmlWhitespaceSensitivity === "ignore") {
-        return [
-          startingTag,
-          indent(printChildren(path, options, print)),
-          hardline,
-          endingTag,
-          escapeNextElementNode,
-        ];
-      }
-
-      return [
-        startingTag,
-        indent(group(printChildren(path, options, print))),
-        endingTag,
-        escapeNextElementNode,
-      ];
+      return [startingTag, indent(group(parts)), endingTag];
     }
 
     case "BlockStatement":
@@ -433,24 +429,6 @@ function printStartingTag(path, print) {
   return ["<", node.tag, indent(attributes), printStartingTagEndMarker(node)];
 }
 
-function printChildren(path, options, print) {
-  const { node } = path;
-  const isEmpty = node.children.every((node) => isWhitespaceNode(node));
-  if (options.htmlWhitespaceSensitivity === "ignore" && isEmpty) {
-    return "";
-  }
-
-  return path.map(({ isFirst }) => {
-    const printedChild = print();
-
-    if (isFirst && options.htmlWhitespaceSensitivity === "ignore") {
-      return [softline, printedChild];
-    }
-
-    return printedChild;
-  }, "children");
-}
-
 function printStartingTagEndMarker(node) {
   if (isVoidElement(node)) {
     return ifBreak([softline, "/>"], [" />", softline]);
diff --git a/tests/format/handlebars/html-whitespace-sensitivity/__snapshots__/format.test.js.snap b/tests/format/handlebars/html-whitespace-sensitivity/__snapshots__/format.test.js.snap
index a7ae19aff..dbbcd5b4a 100644
--- a/tests/format/handlebars/html-whitespace-sensitivity/__snapshots__/format.test.js.snap
+++ b/tests/format/handlebars/html-whitespace-sensitivity/__snapshots__/format.test.js.snap
@@ -209,11 +209,9 @@ expressions. sometimes{{nogaps}}areimportant
   some {{text}}
 </HelloWorld>
 
-<div class="a list of classes">
-</div>
+<div class="a list of classes"></div>
 
-<div class="a list of classes">
-</div>
+<div class="a list of classes"></div>
 
 <span>
   This is your name: {{name}}.
@@ -303,8 +301,7 @@ expressions. sometimes{{nogaps}}areimportant
 
 <table>
   <thead>
-    <tr>
-    </tr>
+    <tr></tr>
   </thead>
 </table>
 ================================================================================