Add generic option to control return value for .json and .parse

src/entrypoints/fetch.d.ts

@@ -1,3 +1,3 @@
 interface Body {
-  json(): Promise<unknown>;
+  json<T = unknown>(): Promise<T>;
 }

src/entrypoints/json-parse.d.ts

@@ -5,8 +5,8 @@ interface JSON {
    * @param reviver A function that transforms the results. This function is called for each member of the object.
    * If a member contains nested objects, the nested objects are transformed before the parent object is.
    */
-  parse(
+  parse<T = unknown>(
     text: string,
     reviver?: (this: any, key: string, value: any) => any,
-  ): unknown;
+  ): T;
 }

src/tests/fetch.ts

@@ -7,10 +7,11 @@ doNotExecute(async () => {
 });
 
 doNotExecute(async () => {
-  // Make tests fail when someone tries to PR res.json<T>
+  type Named = { name: string };
 
   const result = await fetch("/").then((res) => {
-    // @ts-expect-error
-    return res.json<string>();
+    return res.json<Named>();
   });
+
+  type tests = [Expect<Equal<typeof result, Named>>];
 });

src/tests/json-parse.ts

@@ -7,8 +7,9 @@ doNotExecute(() => {
 });
 
 doNotExecute(() => {
-  // Make tests fail when someone tries to PR JSON.parse<T>
+  type Named = { name: string };
 
-  // @ts-expect-error
-  const result = JSON.parse<string>("{}");
+  const result = JSON.parse<Named>("{ name: 'ts-reset' }");
+
+  type tests = [Expect<Equal<typeof result, Named>>];
 });