From dd5e24eabeab1f75ad573c79781e5fd408bcfad3 Mon Sep 17 00:00:00 2001
From: Konv Suu <hi@kovsu.com>
Date: Tue, 14 Jul 2026 17:33:39 +0800
Subject: [PATCH] Preserve quotes for `TSMethodSignature` nodes named `new`
 (#19621)

---
 changelog_unreleased/typescript/19621.md      | 19 ++++
 src/language-js/print/key.js                  |  4 +
 .../__snapshots__/format.test.js.snap         | 90 +++++++++++++++++++
 .../typescript/quote-props/issue-19618.ts     |  9 ++
 4 files changed, 122 insertions(+)
 create mode 100644 changelog_unreleased/typescript/19621.md
 create mode 100644 tests/format/typescript/quote-props/issue-19618.ts

diff --git a/changelog_unreleased/typescript/19621.md b/changelog_unreleased/typescript/19621.md
new file mode 100644
index 000000000..912283777
--- /dev/null
+++ b/changelog_unreleased/typescript/19621.md
@@ -0,0 +1,19 @@
+#### Preserve quotes for methods named `new` (#19621 by @kovsu)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+interface Container {
+  "new"(id: string): number;
+}
+
+// Prettier stable
+interface Container {
+  new(id: string): number;
+}
+
+// Prettier main
+interface Container {
+  "new"(id: string): number;
+}
+```
diff --git a/src/language-js/print/key.js b/src/language-js/print/key.js
index 06d6576b3..d7220523f 100644
--- a/src/language-js/print/key.js
+++ b/src/language-js/print/key.js
@@ -99,6 +99,10 @@ function isKeySafeToUnquote(node, options) {
     return false;
   }
 
+  if (node.type === "TSMethodSignature" && value === "new") {
+    return false;
+  }
+
   // Safe to unquote as identifier
   if (
     // With `--strictPropertyInitialization`, TS treats properties with quoted names differently than unquoted ones.
diff --git a/tests/format/typescript/quote-props/__snapshots__/format.test.js.snap b/tests/format/typescript/quote-props/__snapshots__/format.test.js.snap
index c16f0e764..c7a81ca3f 100644
--- a/tests/format/typescript/quote-props/__snapshots__/format.test.js.snap
+++ b/tests/format/typescript/quote-props/__snapshots__/format.test.js.snap
@@ -240,6 +240,96 @@ interface I2 {
 ================================================================================
 `;
 
+exports[`issue-19618.ts - {"quoteProps":"as-needed"} format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+quoteProps: "as-needed"
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  'new'(id: string): number;
+  'method'(): void;
+};
+
+=====================================output=====================================
+interface Container {
+  "new"(id: string): number;
+  method(): void;
+}
+
+type ContainerType = {
+  "new"(id: string): number;
+  method(): void;
+};
+
+================================================================================
+`;
+
+exports[`issue-19618.ts - {"quoteProps":"consistent"} format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+quoteProps: "consistent"
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  'new'(id: string): number;
+  'method'(): void;
+};
+
+=====================================output=====================================
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  "new"(id: string): number;
+  "method"(): void;
+};
+
+================================================================================
+`;
+
+exports[`issue-19618.ts - {"quoteProps":"preserve"} format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+quoteProps: "preserve"
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  'new'(id: string): number;
+  'method'(): void;
+};
+
+=====================================output=====================================
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  "new"(id: string): number;
+  "method"(): void;
+};
+
+================================================================================
+`;
+
 exports[`type-literal.ts - {"quoteProps":"as-needed"} format 1`] = `
 ====================================options=====================================
 parsers: ["typescript"]
diff --git a/tests/format/typescript/quote-props/issue-19618.ts b/tests/format/typescript/quote-props/issue-19618.ts
new file mode 100644
index 000000000..c0b71e365
--- /dev/null
+++ b/tests/format/typescript/quote-props/issue-19618.ts
@@ -0,0 +1,9 @@
+interface Container {
+  "new"(id: string): number;
+  "method"(): void;
+}
+
+type ContainerType = {
+  'new'(id: string): number;
+  'method'(): void;
+};