fix(http): keep the existing query string when adding params on web

core/src/core-plugins.ts

@@ -404,7 +404,8 @@ export class CapacitorHttpPluginWeb extends WebPlugin implements CapacitorHttpPl
   async request(options: HttpOptions): Promise<HttpResponse> {
     const requestInit = buildRequestInit(options, options.webFetchExtra);
     const urlParams = buildUrlParams(options.params, options.shouldEncodeUrlParams);
-    const url = urlParams ? `${options.url}?${urlParams}` : options.url;
+    const separator = options.url.includes('?') ? '&' : '?';
+    const url = urlParams ? `${options.url}${separator}${urlParams}` : options.url;
 
     const response = await fetch(url, requestInit);
     const contentType = response.headers.get('content-type') || '';

core/src/tests/http.spec.ts

@@ -0,0 +1,42 @@
+/**
+ * @jest-environment jsdom
+ */
+
+import { CapacitorHttpPluginWeb } from '../core-plugins';
+
+describe('CapacitorHttpPluginWeb', () => {
+  const originalFetch = (globalThis as any).fetch;
+  let fetchMock: jest.Mock;
+
+  beforeEach(() => {
+    fetchMock = jest.fn(async (url: string) => ({
+      ok: true,
+      status: 200,
+      url,
+      headers: {
+        get: () => 'text/plain',
+        forEach: () => undefined,
+      },
+      text: async () => 'ok',
+    }));
+    (globalThis as any).fetch = fetchMock;
+  });
+
+  afterEach(() => {
+    (globalThis as any).fetch = originalFetch;
+  });
+
+  it('appends params to a url without a query string', async () => {
+    const http = new CapacitorHttpPluginWeb();
+    await http.get({ url: 'https://example.com/api', params: { b: '2' } });
+
+    expect(fetchMock.mock.calls[0][0]).toEqual('https://example.com/api?b=2');
+  });
+
+  it('keeps the existing query string when adding params', async () => {
+    const http = new CapacitorHttpPluginWeb();
+    await http.get({ url: 'https://example.com/api?a=1', params: { b: '2' } });
+
+    expect(fetchMock.mock.calls[0][0]).toEqual('https://example.com/api?a=1&b=2');
+  });
+});