Patch fails with error decoding patch: json: cannot unmarshal object into Go value of type []handlers.jsonPatchOp

[yubinnng]

Describe the bug

I would like to patch a resource with a request body in JSON Merge Patch, RFC 7386 format. However, even if I specify the Content-Type application/merge-patch+json in a PromiseMiddlewareWrapper, add it into a ServerConfiguration and then use the configuration in the client method k8sApi.patchNamespacedPod({xxx}, configuration), the error still occurs:

ApiException [Error]: HTTP-Code: 400
Message: Unknown API Status Code!
Body: "{\"kind\":\"Status\",\"apiVersion\":\"v1\",\"metadata\":{},\"status\":\"Failure\",\"message\":\"error decoding patch: json: cannot unmarshal object into Go value of type []handlers.jsonPatchOp\",\"reason\":\"BadRequest\",\"code\":400}\n"
Headers: {"audit-id":"f2f1b40e-9d4a-49cf-af2b-989bed7de17e","cache-control":"no-cache, private","connection":"close","content-length":"211","content-type":"application/json","date":"Tue, 14 Jan 2025 02:17:01 GMT","x-kubernetes-pf-flowschema-uid":"93068417-329d-4e0f-9768-8a2b6794f954","x-kubernetes-pf-prioritylevel-uid":"f7dc9ee7-016c-48fa-afc3-77112540d77f"}
    at CoreV1ApiResponseProcessor.patchNamespacedPodWithHttpInfo (/Users/I584817/Downloads/js-examples/node_modules/@kubernetes/client-node/dist/gen/apis/CoreV1Api.js:15722:15)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
    at async file:///Users/XXX/Downloads/js-examples/merge-patch-example.js:46:5 {
  code: 400,
  body: '{"kind":"Status","apiVersion":"v1","metadata":{},"status":"Failure","message":"error decoding patch: json: cannot unmarshal object into Go value of type []handlers.jsonPatchOp","reason":"BadRequest","code":400}\n',
  headers: {
    'audit-id': 'f2f1b40e-9d4a-49cf-af2b-989bed7de17e',
    'cache-control': 'no-cache, private',
    connection: 'close',
    'content-length': '211',
    'content-type': 'application/json',
    date: 'Tue, 14 Jan 2025 02:17:01 GMT',
    'x-kubernetes-pf-flowschema-uid': '93068417-329d-4e0f-9768-8a2b6794f954',
    'x-kubernetes-pf-prioritylevel-uid': 'f7dc9ee7-016c-48fa-afc3-77112540d77f'
  }
}

Please find my code in the example code below.

I tried to debug, and it seems that the pre function in the PromiseMiddlewareWrapper does not be executed.

I saw a Patch related issue [release-1.x] Patch namespace secret trigger an error due to unsupported media type, but it does not solve this issue.

Client Version
1.0.0

Server Version
1.31.0

To Reproduce

Save the below example code into file merge-patch-example.js, then execute the following commands.

npm i @kubernetes/client-node
node merge-patch-example.js

Expected behavior
The server should not raise any error.

Example Code

import * as k8s from '@kubernetes/client-node';
import { PromiseMiddlewareWrapper } from '@kubernetes/client-node/dist/gen/middleware.js';

const kc = new k8s.KubeConfig();
kc.loadFromDefault();

const k8sApi = kc.makeApiClient(k8s.CoreV1Api);

const namespace = 'default';

try {
    const res = await k8sApi.listNamespacedPod({ namespace });
    const body = {
        metadata: {
            labels: {
                foo: 'bar2'
            }
        }
    };
    const headerPatchMiddleware = new PromiseMiddlewareWrapper({
        pre: async (requestContext) => {
            requestContext.setHeaderParam('Content-type', 'application/merge-patch+json');
            return requestContext;
        },
        post: async (responseContext) => responseContext,
    });
    let currentContext = kc.getCurrentContext();
    let currentCluster = kc.getCluster(currentContext);
    if (currentCluster === undefined || currentCluster === null) {
        throw new Error('Cluster is undefined');
    }
    let server = currentCluster.server;
    if (server === undefined) {
        throw new Error('Server is undefined');
    }

    const baseServerConfig = new k8s.ServerConfiguration(server, {});
    const configuration = k8s.createConfiguration({
        middleware: [headerPatchMiddleware],
        baseServer: baseServerConfig,
        authMethods: {
            default: kc,
        },
    });

    await k8sApi
        .patchNamespacedPod(
            { name: res?.items?.[0].metadata?.name ?? '', namespace, body: body },
            configuration,
        )
    console.log('Merged.');
} catch (err) {
    console.error('Error: ');
    console.error(err);
}

Environment (please complete the following information):

• OS: MacOS
• Node.js version 22.13.0
• Cloud runtime: Local Minikube

[yubinnng]