fix(openapi-fetch): avoid errors parsing empty JSON bodies (200 with no content)

Author: jbarba

.changeset/wet-waves-turn.md

@@ -0,0 +1,5 @@
+---
+"openapi-fetch": patch
+---
+
+Use text() when no content-length is provided to avoid errors parsing empty bodies (200 with no content)

packages/openapi-fetch/src/index.js

@@ -230,18 +230,27 @@ export default function createClient(clientOptions) {
       }
     }
 
+    const contentLength = response.headers.get("Content-Length");
     // handle empty content
-    if (response.status === 204 || request.method === "HEAD" || response.headers.get("Content-Length") === "0") {
+    if (response.status === 204 || request.method === "HEAD" || contentLength === "0") {
       return response.ok ? { data: undefined, response } : { error: undefined, response };
     }
 
     // parse response (falling back to .text() when necessary)
     if (response.ok) {
-      // if "stream", skip parsing entirely
-      if (parseAs === "stream") {
-        return { data: response.body, response };
-      }
-      return { data: await response[parseAs](), response };
+      const parseData = async () => {
+        // if "stream", skip parsing entirely
+        if (parseAs === "stream") return response.body;
+
+        if (parseAs === "json" && !contentLength) {
+          // use text() when no content-length is provided to avoid errors parsing empty bodies (200 with no content)
+          const raw = await response.text();
+          return raw ? JSON.parse(raw) : undefined;
+        }
+
+        return await response[parseAs]();
+      };
+      return { data: await parseData(), response };
     }
 
     // handle errors

packages/openapi-fetch/test/common/request.test.ts

@@ -342,6 +342,7 @@ describe("request", () => {
         clone: () => ({ ...response }),
         headers: new Headers(),
         json: async () => data,
+        text: async () => JSON.stringify(data),
         status: 200,
         ok: true,
       } as Response;

packages/openapi-fetch/test/common/response.test.ts

@@ -138,6 +138,18 @@ describe("response", () => {
   describe("parseAs", () => {
     const client = createObservedClient<paths>({}, async () => Response.json({}));
 
+    test("json with empty response", async () => {
+      const client = createObservedClient<paths>({}, async () => new Response());
+      const { data, error } = (await client.GET("/empty-json", {
+        parseAs: "json",
+      })) satisfies { data?: undefined };
+      if (error) {
+        throw new Error("parseAs json: error");
+      }
+
+      expect(data).toBe(undefined);
+    });
+
     test("text", async () => {
       const { data, error } = (await client.GET("/resources", {
         parseAs: "text",

packages/openapi-fetch/test/common/schemas/common.d.ts

@@ -727,6 +727,22 @@ export interface paths {
         patch?: never;
         trace?: never;
     };
+    "/empty-json": {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        get: operations["getEmptyJsonResponse"];
+        put?: never;
+        post?: never;
+        delete?: never;
+        options?: never;
+        head?: never;
+        patch?: never;
+        trace?: never;
+    };
 }
 export type webhooks = Record<string, never>;
 export interface components {
@@ -779,4 +795,30 @@ export interface operations {
             };
         };
     };
+    getEmptyJsonResponse: {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        requestBody?: never;
+        responses: {
+            /** @description Empty JSON Response */
+            200: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content?: never;
+            };
+            default: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": components["schemas"]["Error"];
+                };
+            };
+        };
+    };
 }

packages/openapi-fetch/test/common/schemas/common.yaml

@@ -421,6 +421,17 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/Error"
+  /empty-json:
+    get:
+      operationId: getEmptyJsonResponse
+      responses:
+        200:
+          description: Empty JSON Response
+        default:
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
 components:
   schemas:
     Error: