From 78ff25b5cfed91e047ac7776b95f7108579f00bc Mon Sep 17 00:00:00 2001
From: fisker Cheung <lionkay@gmail.com>
Date: Tue, 13 Jan 2026 20:47:40 +0800
Subject: [PATCH] Don't force array/object with short block comment to break
 (#18617)

---
 changelog_unreleased/javascript/18617.md      | 20 ++++++
 src/language-js/print/array.js                | 30 ++++-----
 src/language-js/print/object.js               | 17 +++--
 tests/config/run-format-test.js               |  1 +
 .../enums/__snapshots__/format.test.js.snap   |  4 +-
 .../__snapshots__/format.test.js.snap         | 16 ++---
 .../in-list/__snapshots__/format.test.js.snap | 63 +++++++++++++++++++
 .../in-list/dangling-comment-in-list.js       | 23 +++++++
 .../format/js/comments/in-list/format.test.js |  1 +
 .../tuple/__snapshots__/format.test.js.snap   | 24 ++-----
 10 files changed, 145 insertions(+), 54 deletions(-)
 create mode 100644 changelog_unreleased/javascript/18617.md
 create mode 100644 tests/format/js/comments/in-list/__snapshots__/format.test.js.snap
 create mode 100644 tests/format/js/comments/in-list/dangling-comment-in-list.js
 create mode 100644 tests/format/js/comments/in-list/format.test.js

diff --git a/changelog_unreleased/javascript/18617.md b/changelog_unreleased/javascript/18617.md
new file mode 100644
index 000000000..400979305
--- /dev/null
+++ b/changelog_unreleased/javascript/18617.md
@@ -0,0 +1,20 @@
+#### Don't force empty array and object with short comments to break (#18617 by @fisker)
+
+<!-- prettier-ignore -->
+```jsx
+// Input
+const array = [/* comment */]
+const object = {/* comment */}
+
+// Prettier stable
+const array = [
+  /* comment */
+];
+const object = {
+  /* comment */
+};
+
+// Prettier main
+const array = [/* comment */];
+const object = {/* comment */};
+```
diff --git a/src/language-js/print/array.js b/src/language-js/print/array.js
index e02bd6683..b0d60bc8e 100644
--- a/src/language-js/print/array.js
+++ b/src/language-js/print/array.js
@@ -28,16 +28,20 @@ import { printTypeAnnotationProperty } from "./type-annotation.js";
 
 /** @import {Doc} from "../../document/index.js" */
 
-function printEmptyArrayElements(path, options, openBracket, closeBracket) {
+function printEmptyArrayElements(path, options) {
   const { node } = path;
-  if (!hasComment(node, CommentCheckFlags.Dangling)) {
-    return [openBracket, closeBracket];
-  }
+
   return group([
-    openBracket,
-    printDanglingComments(path, options, { indent: true }),
-    softline,
-    closeBracket,
+    "[",
+    hasComment(node, CommentCheckFlags.Dangling)
+      ? [
+          indent([softline, printDanglingComments(path, options)]),
+          hasComment(node, CommentCheckFlags.Dangling | CommentCheckFlags.Line)
+            ? hardline
+            : softline,
+        ]
+      : [],
+    "]",
   ]);
 }
 
@@ -52,14 +56,10 @@ function printArray(path, options, print) {
   /** @type{Doc[]} */
   const parts = [];
 
-  const openBracket = "[";
-  const closeBracket = "]";
   const elementsProperty = isTupleType(node) ? "elementTypes" : "elements";
   const elements = node[elementsProperty];
   if (elements.length === 0 && !node.inexact) {
-    parts.push(
-      printEmptyArrayElements(path, options, openBracket, closeBracket),
-    );
+    parts.push(printEmptyArrayElements(path, options));
   } else {
     const lastElem = elements.at(-1);
     const canHaveTrailingComma =
@@ -116,7 +116,7 @@ function printArray(path, options, print) {
     parts.push(
       group(
         [
-          openBracket,
+          "[",
           indent([
             softline,
             shouldUseConciseFormatting
@@ -134,7 +134,7 @@ function printArray(path, options, print) {
             printDanglingComments(path, options),
           ]),
           softline,
-          closeBracket,
+          "]",
         ],
         { shouldBreak, id: groupId },
       ),
diff --git a/src/language-js/print/object.js b/src/language-js/print/object.js
index ce93bca21..3e0ab1334 100644
--- a/src/language-js/print/object.js
+++ b/src/language-js/print/object.js
@@ -134,14 +134,19 @@ function printObject(path, options, print) {
 
   let content;
   if (parts.length === 0) {
-    if (!hasComment(node, CommentCheckFlags.Dangling)) {
-      return ["{}", printTypeAnnotationProperty(path, print)];
-    }
-
     content = group([
       "{",
-      printDanglingComments(path, options, { indent: true }),
-      softline,
+      hasComment(node, CommentCheckFlags.Dangling)
+        ? [
+            indent([softline, printDanglingComments(path, options)]),
+            hasComment(
+              node,
+              CommentCheckFlags.Dangling | CommentCheckFlags.Line,
+            )
+              ? hardline
+              : softline,
+          ]
+        : [],
       "}",
       printOptionalToken(path),
       printTypeAnnotationProperty(path, print),
diff --git a/tests/config/run-format-test.js b/tests/config/run-format-test.js
index 921b00d63..780c39142 100644
--- a/tests/config/run-format-test.js
+++ b/tests/config/run-format-test.js
@@ -27,6 +27,7 @@ const unstableTests = new Map(
     "js/comments/return-statement.js",
     "js/comments/tagged-template-literal.js",
     "js/for/9812-unstable.js",
+    "js/comments/in-list/dangling-comment-in-list.js",
     [
       "js/multiparser-markdown/codeblock.js",
       (options) => options.proseWrap === "always",
diff --git a/tests/format/flow/enums/__snapshots__/format.test.js.snap b/tests/format/flow/enums/__snapshots__/format.test.js.snap
index db6cd6c3d..91fe51a01 100644
--- a/tests/format/flow/enums/__snapshots__/format.test.js.snap
+++ b/tests/format/flow/enums/__snapshots__/format.test.js.snap
@@ -148,9 +148,7 @@ enum E2 of number {
   // D = 100
 }
 
-enum E3 {
-  /*Q*/
-}
+enum E3 {/*Q*/}
 
 enum E4 of string {
   /*Q*/ Foo = "foo",
diff --git a/tests/format/js/comments/__snapshots__/format.test.js.snap b/tests/format/js/comments/__snapshots__/format.test.js.snap
index 69c5002ac..52bb23f5a 100644
--- a/tests/format/js/comments/__snapshots__/format.test.js.snap
+++ b/tests/format/js/comments/__snapshots__/format.test.js.snap
@@ -1580,15 +1580,11 @@ Thing(/* dangling */);
 export /* dangling */{};
 
 =====================================output=====================================
-var a = {
-  /* dangling */
-}
+var a = {/* dangling */}
 var b = {
   // dangling
 }
-var b = [
-  /* dangling */
-]
+var b = [/* dangling */]
 function d() {
   /* dangling */
 }
@@ -1618,15 +1614,11 @@ Thing(/* dangling */);
 export /* dangling */{};
 
 =====================================output=====================================
-var a = {
-  /* dangling */
-};
+var a = {/* dangling */};
 var b = {
   // dangling
 };
-var b = [
-  /* dangling */
-];
+var b = [/* dangling */];
 function d() {
   /* dangling */
 }
diff --git a/tests/format/js/comments/in-list/__snapshots__/format.test.js.snap b/tests/format/js/comments/in-list/__snapshots__/format.test.js.snap
new file mode 100644
index 000000000..4a973e97c
--- /dev/null
+++ b/tests/format/js/comments/in-list/__snapshots__/format.test.js.snap
@@ -0,0 +1,63 @@
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
+
+exports[`dangling-comment-in-list.js format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+array = [/* array */]
+object = {/* object */}
+call = call(/* call argument */)
+fn = function(/* function parameter */) {}
+newFoo = new Foo(/* new argument */)
+
+// TODO[@fisker]: fix the following
+array = [
+/* array */]
+object = {
+/* object */}
+call = call(
+/* call argument */)
+fn = function(
+/* function parameter */) {}
+newFoo = new Foo
+(/* new argument */)
+
+array = [/* array long long long long long long long long long long long long long long */]
+object = {/* object long long long long long long long long long long long long long long */}
+call = call(/* call argument long long long long long long long long long long long long long long */)
+fn = function (/* function long parameter long long long long long long long long long long long long long */) {}
+newFoo = new Foo(/* new argument long long long long long long long long long long long long long long */)
+
+=====================================output=====================================
+array = [/* array */];
+object = {/* object */};
+call = call(/* call argument */);
+fn = function (/* function parameter */) {};
+newFoo = new Foo(/* new argument */);
+
+// TODO[@fisker]: fix the following
+array = [/* array */];
+object = {/* object */};
+call =
+  call();
+  /* call argument */
+fn = function () /* function parameter */ {};
+newFoo = new Foo(/* new argument */);
+
+array = [
+  /* array long long long long long long long long long long long long long long */
+];
+object = {
+  /* object long long long long long long long long long long long long long long */
+};
+call =
+  call(/* call argument long long long long long long long long long long long long long long */);
+fn =
+  function (/* function long parameter long long long long long long long long long long long long long */) {};
+newFoo =
+  new Foo(/* new argument long long long long long long long long long long long long long long */);
+
+================================================================================
+`;
diff --git a/tests/format/js/comments/in-list/dangling-comment-in-list.js b/tests/format/js/comments/in-list/dangling-comment-in-list.js
new file mode 100644
index 000000000..46c665cf1
--- /dev/null
+++ b/tests/format/js/comments/in-list/dangling-comment-in-list.js
@@ -0,0 +1,23 @@
+array = [/* array */]
+object = {/* object */}
+call = call(/* call argument */)
+fn = function(/* function parameter */) {}
+newFoo = new Foo(/* new argument */)
+
+// TODO[@fisker]: fix the following
+array = [
+/* array */]
+object = {
+/* object */}
+call = call(
+/* call argument */)
+fn = function(
+/* function parameter */) {}
+newFoo = new Foo
+(/* new argument */)
+
+array = [/* array long long long long long long long long long long long long long long */]
+object = {/* object long long long long long long long long long long long long long long */}
+call = call(/* call argument long long long long long long long long long long long long long long */)
+fn = function (/* function long parameter long long long long long long long long long long long long long */) {}
+newFoo = new Foo(/* new argument long long long long long long long long long long long long long long */)
diff --git a/tests/format/js/comments/in-list/format.test.js b/tests/format/js/comments/in-list/format.test.js
new file mode 100644
index 000000000..67c251cce
--- /dev/null
+++ b/tests/format/js/comments/in-list/format.test.js
@@ -0,0 +1 @@
+runFormatTest(import.meta, ["babel", "flow", "typescript"]);
diff --git a/tests/format/typescript/tuple/__snapshots__/format.test.js.snap b/tests/format/typescript/tuple/__snapshots__/format.test.js.snap
index c28c7dae0..0f7368aa9 100644
--- a/tests/format/typescript/tuple/__snapshots__/format.test.js.snap
+++ b/tests/format/typescript/tuple/__snapshots__/format.test.js.snap
@@ -36,9 +36,7 @@ type Foo6 = [
 
 
 =====================================output=====================================
-type Foo1 = [
-  /* comment */
-];
+type Foo1 = [/* comment */];
 
 type Foo2 = [
   // comment
@@ -54,9 +52,7 @@ type Foo4 = [
   // comment2
 ];
 
-type Foo5 = [
-  /* comment1 */
-];
+type Foo5 = [/* comment1 */];
 
 type Foo6 = [
   /* comment1 */
@@ -102,9 +98,7 @@ type Foo6 = [
 
 
 =====================================output=====================================
-type Foo1 = [
-  /* comment */
-];
+type Foo1 = [/* comment */];
 
 type Foo2 = [
   // comment
@@ -120,9 +114,7 @@ type Foo4 = [
   // comment2
 ];
 
-type Foo5 = [
-  /* comment1 */
-];
+type Foo5 = [/* comment1 */];
 
 type Foo6 = [
   /* comment1 */
@@ -168,9 +160,7 @@ type Foo6 = [
 
 
 =====================================output=====================================
-type Foo1 = [
-  /* comment */
-];
+type Foo1 = [/* comment */];
 
 type Foo2 = [
   // comment
@@ -186,9 +176,7 @@ type Foo4 = [
   // comment2
 ];
 
-type Foo5 = [
-  /* comment1 */
-];
+type Foo5 = [/* comment1 */];
 
 type Foo6 = [
   /* comment1 */