From ceed4053952f471fe9fffca0df0d8da220bd5c5a Mon Sep 17 00:00:00 2001
From: auvred <61150013+auvred@users.noreply.github.com>
Date: Fri, 21 Jul 2023 19:43:26 +0300
Subject: [PATCH] Add typing to support `readonly` array properties of AST Node
 (#15127)

* Add typing to support `readonly` array properties of AST Node

* add changelog

* fix changelog

* add test case
---
 changelog_unreleased/api/15127.md | 32 +++++++++++++++++++++++++++++++
 src/index.d.ts                    |  2 +-
 tests/dts/unit/cases/print.ts     |  3 +++
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 changelog_unreleased/api/15127.md

diff --git a/changelog_unreleased/api/15127.md b/changelog_unreleased/api/15127.md
new file mode 100644
index 000000000..4e341bd97
--- /dev/null
+++ b/changelog_unreleased/api/15127.md
@@ -0,0 +1,32 @@
+#### Add typing to support `readonly` array properties of AST Node (#15127 by @auvred)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+
+// Prettier stable
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+//                  ^ Argument of type '"readonlyArray"' is not assignable to parameter of type '"regularArray"'. ts(2345)
+
+// Prettier main
+interface TestNode {
+  readonlyArray: readonly string[];
+}
+
+declare const path: AstPath<TestNode>;
+
+path.map(() => "", "readonlyArray");
+```
diff --git a/src/index.d.ts b/src/index.d.ts
index 0b0c989a8..c36839544 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -33,7 +33,7 @@ type ArrayElement<T> = T extends Array<infer E> ? E : never;
 
 // A union of the properties of the given object that are arrays.
 type ArrayProperties<T> = {
-  [K in keyof T]: NonNullable<T[K]> extends any[] ? K : never;
+  [K in keyof T]: NonNullable<T[K]> extends readonly any[] ? K : never;
 }[keyof T];
 
 // A union of the properties of the given array T that can be used to index it.
diff --git a/tests/dts/unit/cases/print.ts b/tests/dts/unit/cases/print.ts
index 25679963e..fb75c93fb 100644
--- a/tests/dts/unit/cases/print.ts
+++ b/tests/dts/unit/cases/print.ts
@@ -12,6 +12,7 @@ interface Nested2 {
   kind: "2";
   item3: Nested3;
   list3: Nested3[];
+  list5: readonly Nested3[];
 }
 interface Nested3 {
   kind: "3";
@@ -155,5 +156,7 @@ function print(
   // @ts-expect-error
   path.map(print, "item2", "item3");
 
+  path.map(print, "item2", "list5");
+
   return "";
 }