From 230bba53a9f71bc7e22923b0f10d605bb67411f0 Mon Sep 17 00:00:00 2001
From: fisker Cheung <lionkay@gmail.com>
Date: Tue, 27 May 2025 10:46:57 +0800
Subject: [PATCH] Forbid new line before arrow (#17516)

---
 src/language-js/parse/babel.js                |  1 -
 .../__snapshots__/format.test.js.snap         | 51 ------------
 .../newline-before-arrow/format.test.js       |  8 --
 .../__snapshots__/format.test.js.snap         | 80 +++++++++++++++++++
 .../js/newline-before-arrow/format.test.js    | 11 +++
 .../newline-before-arrow.js                   |  0
 6 files changed, 91 insertions(+), 60 deletions(-)
 delete mode 100644 tests/format/js/arrows/newline-before-arrow/__snapshots__/format.test.js.snap
 delete mode 100644 tests/format/js/arrows/newline-before-arrow/format.test.js
 create mode 100644 tests/format/misc/errors/js/newline-before-arrow/__snapshots__/format.test.js.snap
 create mode 100644 tests/format/misc/errors/js/newline-before-arrow/format.test.js
 rename tests/format/{js/arrows => misc/errors/js}/newline-before-arrow/newline-before-arrow.js (100%)

diff --git a/src/language-js/parse/babel.js b/src/language-js/parse/babel.js
index 894c8c58b..312c328e7 100644
--- a/src/language-js/parse/babel.js
+++ b/src/language-js/parse/babel.js
@@ -187,7 +187,6 @@ const allowedReasonCodes = new Set([
   "UnterminatedJsxContent",
   "UnexpectedReservedWord",
   "ModuleAttributesWithDuplicateKeys",
-  "LineTerminatorBeforeArrow",
   "InvalidEscapeSequenceTemplate",
   "NonAbstractClassHasAbstractMethod",
   "OptionalTypeBeforeRequired",
diff --git a/tests/format/js/arrows/newline-before-arrow/__snapshots__/format.test.js.snap b/tests/format/js/arrows/newline-before-arrow/__snapshots__/format.test.js.snap
deleted file mode 100644
index a9553bd32..000000000
--- a/tests/format/js/arrows/newline-before-arrow/__snapshots__/format.test.js.snap
+++ /dev/null
@@ -1,51 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`newline-before-arrow.js [acorn] format 1`] = `
-"Unexpected token (2:1)
-  1 | async x
-> 2 | => x
-    | ^
-  3 |
-Cause: Unexpected token (2:0)"
-`;
-
-exports[`newline-before-arrow.js [espree] format 1`] = `
-"Unexpected token => (2:1)
-  1 | async x
-> 2 | => x
-    | ^
-  3 |
-Cause: Unexpected token =>"
-`;
-
-exports[`newline-before-arrow.js [meriyah] format 1`] = `
-"No line break is allowed after '=>' (2:1)
-  1 | async x
-> 2 | => x
-    | ^^
-  3 |
-Cause: [2:0-2:2]: No line break is allowed after '=>'"
-`;
-
-exports[`newline-before-arrow.js [oxc] format 1`] = `
-"Line terminator not permitted before arrow (2:1)
-  1 | async x
-> 2 | => x
-    | ^^
-  3 |"
-`;
-
-exports[`newline-before-arrow.js format 1`] = `
-====================================options=====================================
-parsers: ["babel"]
-printWidth: 80
-                                                                                | printWidth
-=====================================input======================================
-async x
-=> x
-
-=====================================output=====================================
-async (x) => x;
-
-================================================================================
-`;
diff --git a/tests/format/js/arrows/newline-before-arrow/format.test.js b/tests/format/js/arrows/newline-before-arrow/format.test.js
deleted file mode 100644
index ac9301599..000000000
--- a/tests/format/js/arrows/newline-before-arrow/format.test.js
+++ /dev/null
@@ -1,8 +0,0 @@
-runFormatTest(import.meta, ["babel"], {
-  errors: {
-    acorn: ["newline-before-arrow.js"],
-    espree: ["newline-before-arrow.js"],
-    meriyah: ["newline-before-arrow.js"],
-    oxc: ["newline-before-arrow.js"],
-  },
-});
diff --git a/tests/format/misc/errors/js/newline-before-arrow/__snapshots__/format.test.js.snap b/tests/format/misc/errors/js/newline-before-arrow/__snapshots__/format.test.js.snap
new file mode 100644
index 000000000..41c61f39c
--- /dev/null
+++ b/tests/format/misc/errors/js/newline-before-arrow/__snapshots__/format.test.js.snap
@@ -0,0 +1,80 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`newline-before-arrow.js [acorn] format 1`] = `
+"Unexpected token (2:1)
+  1 | async x
+> 2 | => x
+    | ^
+  3 |
+Cause: Unexpected token (2:0)"
+`;
+
+exports[`newline-before-arrow.js [babel] format 1`] = `
+"No line break is allowed before '=>'. (2:3)
+  1 | async x
+> 2 | => x
+    |   ^
+  3 |
+Cause: No line break is allowed before '=>'. (2:2)"
+`;
+
+exports[`newline-before-arrow.js [babel-ts] format 1`] = `
+"No line break is allowed before '=>'. (2:3)
+  1 | async x
+> 2 | => x
+    |   ^
+  3 |
+Cause: No line break is allowed before '=>'. (2:2)"
+`;
+
+exports[`newline-before-arrow.js [babel-ts] format 2`] = `
+"No line break is allowed before '=>'. (2:3)
+  1 | async x
+> 2 | => x
+    |   ^
+  3 |
+Cause: No line break is allowed before '=>'. (2:2)"
+`;
+
+exports[`newline-before-arrow.js [espree] format 1`] = `
+"Unexpected token => (2:1)
+  1 | async x
+> 2 | => x
+    | ^
+  3 |
+Cause: Unexpected token =>"
+`;
+
+exports[`newline-before-arrow.js [flow] format 1`] = `
+"Illegal newline before arrow (2:1)
+  1 | async x
+> 2 | => x
+    | ^^
+  3 |"
+`;
+
+exports[`newline-before-arrow.js [meriyah] format 1`] = `
+"No line break is allowed after '=>' (2:1)
+  1 | async x
+> 2 | => x
+    | ^^
+  3 |
+Cause: [2:0-2:2]: No line break is allowed after '=>'"
+`;
+
+exports[`newline-before-arrow.js [oxc] format 1`] = `
+"Line terminator not permitted before arrow (2:1)
+  1 | async x
+> 2 | => x
+    | ^^
+  3 |"
+`;
+
+exports[`newline-before-arrow.js [typescript] format 1`] = `
+"Unexpected keyword or identifier. (1:1)
+> 1 | async x
+    | ^
+  2 | => x
+  3 |
+Cause: Unexpected keyword or identifier."
+`;
diff --git a/tests/format/misc/errors/js/newline-before-arrow/format.test.js b/tests/format/misc/errors/js/newline-before-arrow/format.test.js
new file mode 100644
index 000000000..c72ea76ae
--- /dev/null
+++ b/tests/format/misc/errors/js/newline-before-arrow/format.test.js
@@ -0,0 +1,11 @@
+runFormatTest(import.meta, [
+  "babel",
+  "typescript",
+  "flow",
+  "babel-ts",
+  "acorn",
+  "espree",
+  "meriyah",
+  "babel-ts",
+  "oxc",
+]);
diff --git a/tests/format/js/arrows/newline-before-arrow/newline-before-arrow.js b/tests/format/misc/errors/js/newline-before-arrow/newline-before-arrow.js
similarity index 100%
rename from tests/format/js/arrows/newline-before-arrow/newline-before-arrow.js
rename to tests/format/misc/errors/js/newline-before-arrow/newline-before-arrow.js