feat: add TypeScript 6 support

.changeset/widen-typescript-peer-dep.md

@@ -0,0 +1,9 @@
+---
+"openapi-typescript": patch
+"openapi-typescript-helpers": patch
+---
+
+feat: add TypeScript 6 support
+
+- Widen peer dep to `^5.x || ^6.x`
+- Fix `Readable<T>` and `Writable<T>` to preserve built-in objects (Date, RegExp, functions) that now match `extends object` in TS6

packages/openapi-fetch/test/helpers.ts

@@ -24,18 +24,18 @@ export function createObservedClient<T extends {}, M extends MediaType = MediaTy
 }
 
 /**
- * Convert a Headers object to a plain object for easier comparison
+ * Convert a Headers object to a plain object for easier comparison.
+ * Uses Headers.forEach rather than Headers.entries because forEach is in base
+ * lib.dom with an identical signature in both TS 5.x and 6.x, while entries
+ * requires DOM.Iterable in TS 5.x.
  */
 export function headersToObj(headers: Headers | Record<string, string>): Record<string, string> {
-  const iter =
-    headers instanceof Headers
-      ? headers
-          // @ts-expect-error FIXME: this is a missing "lib" in tsconfig.json but dunno what
-          .entries()
-      : Object.entries(headers);
-  const result: Record<string, string> = {};
-  for (const [k, v] of iter) {
-    result[k] = v;
+  if (!(headers instanceof Headers)) {
+    return { ...headers };
   }
+  const result: Record<string, string> = {};
+  headers.forEach((value, key) => {
+    result[key] = value;
+  });
   return result;
 }

packages/openapi-typescript-helpers/package.json

@@ -34,6 +34,6 @@
     "lint:ts": "tsc --noEmit"
   },
   "devDependencies": {
-    "typescript": "5.9.3"
+    "typescript": "6.0.2"
   }
 }

packages/openapi-typescript-helpers/src/index.ts

@@ -223,9 +223,11 @@ export type Readable<T> =
       ? Readable<U>
       : T extends (infer E)[]
         ? Readable<E>[]
-        : T extends object
-          ? { [K in keyof T as NonNullable<T[K]> extends $Write<any> ? never : K]: Readable<T[K]> }
-          : T;
+        : T extends Date | RegExp | ((...args: never[]) => unknown)
+          ? T
+          : T extends object
+            ? { [K in keyof T as NonNullable<T[K]> extends $Write<any> ? never : K]: Readable<T[K]> }
+            : T;
 
 /**
  * Resolve type for writing (requests): strips $Read properties, unwraps $Write
@@ -240,8 +242,10 @@ export type Writable<T> =
       ? Writable<U>
       : T extends (infer E)[]
         ? Writable<E>[]
-        : T extends object
-          ? { [K in keyof T as NonNullable<T[K]> extends $Read<any> ? never : K]: Writable<T[K]> } & {
-              [K in keyof T as NonNullable<T[K]> extends $Read<any> ? K : never]?: never;
-            }
-          : T;
+        : T extends Date | RegExp | ((...args: never[]) => unknown)
+          ? T
+          : T extends object
+            ? { [K in keyof T as NonNullable<T[K]> extends $Read<any> ? never : K]: Writable<T[K]> } & {
+                [K in keyof T as NonNullable<T[K]> extends $Read<any> ? K : never]?: never;
+              }
+            : T;

packages/openapi-typescript/package.json

@@ -59,7 +59,7 @@
     "version": "pnpm run build"
   },
   "peerDependencies": {
-    "typescript": "^5.x"
+    "typescript": "^5.x || ^6.x"
   },
   "dependencies": {
     "@redocly/openapi-core": "^1.34.6",