Make json() throw on empty responses

Author: sindresorhus

readme.md

@@ -91,7 +91,7 @@ import ky from 'https://esm.sh/ky';
 
 The `input` and `options` are the same as [`fetch`](https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch), with additional `options` available (see below).
 
-Returns a [`Response` object](https://developer.mozilla.org/en-US/docs/Web/API/Response) with [`Body` methods](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#body) added for convenience. So you can, for example, call `ky.get(input).json()` directly without having to await the `Response` first. When called like that, an appropriate `Accept` header will be set depending on the body method used. Unlike the `Body` methods of `window.fetch`, these will throw an `HTTPError` if the response status is not in the range of `200...299`. Also, `.json()` will return `undefined` if body is empty or the response status is `204` instead of throwing a parse error due to an empty body.
+Returns a [`Response` object](https://developer.mozilla.org/en-US/docs/Web/API/Response) with [`Body` methods](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#body) added for convenience. So you can, for example, call `ky.get(input).json()` directly without having to await the `Response` first. When called like that, an appropriate `Accept` header will be set depending on the body method used. Unlike the `Body` methods of `window.fetch`, these will throw an `HTTPError` if the response status is not in the range of `200...299`. Also, `.json()` throws if the body is empty or the response status is `204`.
 
 Available body shortcuts: `.json()`, `.text()`, `.formData()`, `.arrayBuffer()`, `.blob()`, and `.bytes()`. The `.bytes()` shortcut is only present when the runtime supports `Response.prototype.bytes()`.
 

source/core/Ky.ts

@@ -265,9 +265,13 @@ export class Ky {
 					return response[type]();
 				}
 
-				const text = response.status === 204 ? '' : await response.text();
+				const text = await response.text();
 				if (text === '') {
-					return schema === undefined ? undefined : validateJsonWithSchema(undefined, schema);
+					if (schema !== undefined) {
+						return validateJsonWithSchema(undefined, schema);
+					}
+
+					return JSON.parse(text);
 				}
 
 				const jsonValue = initHookOptions.parseJson
@@ -535,7 +539,14 @@ export class Ky {
 		const request = this.#getResponseRequest(response);
 
 		if (this.#options.parseJson) {
-			response.json = async () => this.#options.parseJson!(await response.text(), {request, response});
+			response.json = async () => {
+				const text = await response.text();
+				if (text === '') {
+					return JSON.parse(text);
+				}
+
+				return this.#options.parseJson!(text, {request, response});
+			};
 		}
 
 		return response;

source/types/ResponsePromise.ts

@@ -1,5 +1,5 @@
 /**
-Returns a `Response` object with `Body` methods added for convenience. So you can, for example, call `ky.get(input).json()` directly without having to await the `Response` first. When called like that, an appropriate `Accept` header will be set depending on the body method used. Unlike the `Body` methods of `window.fetch`, these will throw an `HTTPError` if the response status is not in the range of `200...299`. Also, `.json()` will return `undefined` if body is empty or the response status is `204` instead of throwing a parse error due to an empty body.
+Returns a `Response` object with `Body` methods added for convenience. So you can, for example, call `ky.get(input).json()` directly without having to await the `Response` first. When called like that, an appropriate `Accept` header will be set depending on the body method used. Unlike the `Body` methods of `window.fetch`, these will throw an `HTTPError` if the response status is not in the range of `200...299`. Also, `.json()` throws if the body is empty or the response status is `204`.
 */
 import {type KyResponse} from './response.js';
 import type {StandardSchemaV1, StandardSchemaV1InferOutput} from './standard-schema.js';
@@ -44,7 +44,7 @@ export type ResponsePromise<T = unknown> = {
 		const result2 = await ky<Result>(…).json();
 		```
 		*/
-		<JsonType = T>(): Promise<JsonType | undefined>;
+		<JsonType = T>(): Promise<JsonType>;
 
 		/**
 		Get the response body as JSON and validate it with a Standard Schema.

test/main.ts

@@ -261,7 +261,7 @@ test('.json() when response is chunked', async t => {
 
 	const responseJson = await ky.get<['one', 'two']>(server.url).json();
 
-	expectTypeOf(responseJson).toEqualTypeOf<['one', 'two'] | undefined>();
+	expectTypeOf(responseJson).toEqualTypeOf<['one', 'two']>();
 
 	t.deepEqual(responseJson, ['one', 'two']);
 });
@@ -287,10 +287,12 @@ test('.json() with empty body', async t => {
 		response.end();
 	});
 
-	const responseJson = await ky.get<{foo: string}>(server.url).json();
-	expectTypeOf(responseJson).toEqualTypeOf<{foo: string} | undefined>();
+	const promise = ky.get<{foo: string}>(server.url).json();
+	expectTypeOf(promise).toEqualTypeOf<Promise<{foo: string}>>();
 
-	t.is(responseJson, undefined);
+	await t.throwsAsync(promise, {
+		message: /Unexpected end of JSON input/,
+	});
 });
 
 test('.json() with 204 response and empty body', async t => {
@@ -302,9 +304,9 @@ test('.json() with 204 response and empty body', async t => {
 		response.status(204).end();
 	});
 
-	const responseJson = await ky(server.url).json();
-
-	t.is(responseJson, undefined);
+	await t.throwsAsync(ky(server.url).json(), {
+		message: /Unexpected end of JSON input/,
+	});
 });
 
 test('.json() with 204 response does not call parseJson', async t => {
@@ -314,14 +316,15 @@ test('.json() with 204 response does not call parseJson', async t => {
 	});
 
 	let parseJsonCalled = false;
-	const result = await ky(server.url, {
-		parseJson(text) {
+	await t.throwsAsync(ky(server.url, {
+		parseJson() {
 			parseJsonCalled = true;
-			return JSON.parse(text);
+			return undefined;
 		},
-	}).json();
+	}).json(), {
+		message: /Unexpected end of JSON input/,
+	});
 
-	t.is(result, undefined);
 	t.false(parseJsonCalled);
 });
 
@@ -332,14 +335,15 @@ test('.json() with empty body does not call parseJson', async t => {
 	});
 
 	let parseJsonCalled = false;
-	const result = await ky(server.url, {
-		parseJson(text) {
+	await t.throwsAsync(ky(server.url, {
+		parseJson() {
 			parseJsonCalled = true;
-			return JSON.parse(text);
+			return undefined;
 		},
-	}).json();
+	}).json(), {
+		message: /Unexpected end of JSON input/,
+	});
 
-	t.is(result, undefined);
 	t.false(parseJsonCalled);
 });
 
@@ -579,6 +583,50 @@ test('.json(schema) validates 204 responses as undefined', async t => {
 	t.deepEqual(error?.issues, issues);
 });
 
+test('.json(schema) with empty body does not call parseJson before validation', async t => {
+	const server = await createHttpTestServer(t);
+	server.get('/', (_request, response) => {
+		response.end();
+	});
+
+	let parseJsonCalled = false;
+	const schema = createSchema<string>(value => ({
+		value: value === undefined ? 'empty:undefined' : 'non-empty',
+	}));
+
+	const responseJson = await ky.get(server.url, {
+		parseJson(text) {
+			parseJsonCalled = true;
+			return JSON.parse(text);
+		},
+	}).json(schema);
+
+	t.false(parseJsonCalled);
+	t.is(responseJson, 'empty:undefined');
+});
+
+test('.json(schema) with 204 response does not call parseJson before validation', async t => {
+	const server = await createHttpTestServer(t);
+	server.get('/', (_request, response) => {
+		response.status(204).end();
+	});
+
+	let parseJsonCalled = false;
+	const schema = createSchema<string>(value => ({
+		value: value === undefined ? 'empty:undefined' : 'non-empty',
+	}));
+
+	const responseJson = await ky.get(server.url, {
+		parseJson(text) {
+			parseJsonCalled = true;
+			return JSON.parse(text);
+		},
+	}).json(schema);
+
+	t.false(parseJsonCalled);
+	t.is(responseJson, 'empty:undefined');
+});
+
 test('.json(schema) with invalid JSON body throws parse error before validation', async t => {
 	const server = await createHttpTestServer(t);
 	server.get('/', (_request, response) => {
@@ -2144,6 +2192,27 @@ test('parseJson option with response.json()', async t => {
 	});
 });
 
+test('parseJson option with response.json() does not run on empty body', async t => {
+	const server = await createHttpTestServer(t);
+	server.get('/', (_request, response) => {
+		response.end();
+	});
+
+	let parseJsonCalled = false;
+	const response = await ky.get(server.url, {
+		parseJson() {
+			parseJsonCalled = true;
+			return undefined;
+		},
+	});
+
+	await t.throwsAsync(response.json(), {
+		message: /Unexpected end of JSON input/,
+	});
+
+	t.false(parseJsonCalled);
+});
+
 test('parseJson option with promise.json() shortcut', async t => {
 	const json = {hello: 'world'};