Fix JSON parsing error on empty response bodies without Content-Length header

.changeset/tame-dolives-brake.md

@@ -0,0 +1,5 @@
+---
+"@hey-api/openapi-ts": patch
+---
+
+**plugin(@hey-api/client-next)**: fix: JSON parsing error on empty response bodies without Content-Length header

.changeset/tame-olives-brake.md

@@ -0,0 +1,5 @@
+---
+"@hey-api/openapi-ts": patch
+---
+
+**plugin(@hey-api/client-fetch)**: fix: JSON parsing error on empty response bodies without Content-Length header

.changeset/tame-solives-brake.md

@@ -0,0 +1,5 @@
+---
+"@hey-api/openapi-ts": patch
+---
+
+**plugin(@hey-api/client-ky)**: fix: JSON parsing error on empty response bodies without Content-Length header

examples/openapi-ts-fastify/src/client/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-fetch/src/client/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-ky/src/client/client/client.gen.ts

@@ -251,10 +251,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-next/src/client/client/client.gen.ts

@@ -144,10 +144,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return {
             data: response.body,

examples/openapi-ts-openai/src/client/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-pinia-colada/src/client/client/client.gen.ts

@@ -164,10 +164,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]()
           break
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text()
+          data = text ? JSON.parse(text) : {}
+          break
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-tanstack-react-query/src/client/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-tanstack-svelte-query/src/client/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

examples/openapi-ts-tanstack-vue-query/src/client/client/client.gen.ts

@@ -164,10 +164,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]()
           break
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text()
+          data = text ? JSON.parse(text) : {}
+          break
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/custom-client/src/__tests__/client.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
 
 import { createClient } from '../client';
 
@@ -48,3 +48,66 @@ describe('buildUrl', () => {
     expect(client.buildUrl(options)).toBe(url);
   });
 });
+
+describe('zero-length body handling', () => {
+  const client = createClient({ baseUrl: 'https://example.com' });
+
+  it('returns empty object for zero-length JSON response', async () => {
+    const mockResponse = new Response(null, {
+      headers: {
+        'Content-Length': '0',
+        'Content-Type': 'application/json',
+      },
+      status: 200,
+    });
+
+    const mockFetch = vi.fn().mockResolvedValue(mockResponse);
+
+    const result = await client.request({
+      fetch: mockFetch,
+      method: 'GET',
+      url: '/test',
+    });
+
+    expect(result.data).toEqual({});
+  });
+
+  it('returns empty object for empty JSON response without Content-Length header (status 200)', async () => {
+    // Simulates a server returning an empty body with status 200 and no Content-Length header
+    // This is the scenario described in the issue where response.json() throws
+    const mockResponse = new Response('', {
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      status: 200,
+    });
+
+    const mockFetch = vi.fn().mockResolvedValue(mockResponse);
+
+    const result = await client.request({
+      fetch: mockFetch,
+      method: 'GET',
+      url: '/test',
+    });
+
+    expect(result.data).toEqual({});
+  });
+
+  it('returns empty object for empty response without Content-Length header and no Content-Type (defaults to JSON)', async () => {
+    // Tests the auto-detection behavior when no Content-Type is provided
+    const mockResponse = new Response('', {
+      status: 200,
+    });
+
+    const mockFetch = vi.fn().mockResolvedValue(mockResponse);
+
+    const result = await client.request({
+      fetch: mockFetch,
+      method: 'GET',
+      url: '/test',
+    });
+
+    // When parseAs is 'auto' and no Content-Type header exists, it should handle empty body gracefully
+    expect(result.data).toBeDefined();
+  });
+});

packages/custom-client/src/client.ts

@@ -111,10 +111,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return {
             data: response.body,

packages/openapi-ts-tests/__snapshots__/plugins/@tanstack/meta/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/body-response-text-plain/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/form-data/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/plugins/@hey-api/client-fetch/sdk-nested-classes-instance/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/plugins/@hey-api/client-fetch/sdk-nested-classes/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/plugins/@hey-api/sdk/default/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body

packages/openapi-ts-tests/main/test/__snapshots__/2.0.x/plugins/@hey-api/sdk/instance/client/client.gen.ts

@@ -182,10 +182,16 @@ export const createClient = (config: Config = {}): Client => {
         case 'arrayBuffer':
         case 'blob':
         case 'formData':
-        case 'json':
         case 'text':
           data = await response[parseAs]();
           break;
+        case 'json': {
+          // Some servers return 200 with no Content-Length and empty body.
+          // response.json() would throw; read as text and parse if non-empty.
+          const text = await response.text();
+          data = text ? JSON.parse(text) : {};
+          break;
+        }
         case 'stream':
           return opts.responseStyle === 'data'
             ? response.body