Use TypeScript 6 across all projects

Author: duncanbeevers

packages/openapi-fetch/package.json

@@ -71,7 +71,7 @@
     "openapi-typescript-codegen": "0.30.0",
     "openapi-typescript-fetch": "2.2.1",
     "superagent": "10.3.0",
-    "typescript": "5.9.3",
+    "typescript": "catalog:",
     "undici": "7.25.0",
     "vite": "catalog:"
   }

packages/openapi-fetch/test/helpers.ts

@@ -27,14 +27,12 @@ export function createObservedClient<T extends {}, M extends MediaType = MediaTy
  * Convert a Headers object to a plain object for easier comparison
  */
 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);
+  // Headers is iterable at runtime in both TS 5 and TS 6, but the lib type only
+  // declares Iterable in TS 6's lib.dom. Double-cast bridges the gap.
+  const entries =
+    headers instanceof Headers ? Array.from(headers as unknown as Iterable<[string, string]>) : Object.entries(headers);
   const result: Record<string, string> = {};
-  for (const [k, v] of iter) {
+  for (const [k, v] of entries) {
     result[k] = v;
   }
   return result;

packages/openapi-fetch/test/no-strict-null-checks/tsconfig.json

@@ -1,6 +1,7 @@
 {
   "extends": "../../tsconfig.json",
   "compilerOptions": {
+    "rootDir": "../..",
     "strictNullChecks": false
   },
   "include": ["."],

packages/openapi-fetch/tsconfig.json

@@ -2,7 +2,6 @@
   "compilerOptions": {
     "allowSyntheticDefaultImports": true,
     "declaration": true,
-    "downlevelIteration": false,
     "esModuleInterop": true,
     "lib": ["ESNext", "DOM"],
     "module": "NodeNext",