fix(types): allow to specify partial default headers for instance creation (#4185)

Co-authored-by: Jay <jasonsaayman@gmail.com>

index.d.ts

@@ -137,6 +137,10 @@ export interface AxiosDefaults<D = any> extends Omit<AxiosRequestConfig<D>, 'hea
   headers: HeadersDefaults;
 }
 
+export interface CreateAxiosDefaults<D = any> extends Omit<AxiosRequestConfig<D>, 'headers'> {
+  headers?: AxiosRequestHeaders | Partial<HeadersDefaults>;
+}
+
 export interface AxiosResponse<T = any, D = any>  {
   data: T;
   status: number;
@@ -254,7 +258,7 @@ export interface GenericFormData {
 }
 
 export interface AxiosStatic extends AxiosInstance {
-  create(config?: AxiosRequestConfig): AxiosInstance;
+  create(config?: CreateAxiosDefaults): AxiosInstance;
   Cancel: CancelStatic;
   CancelToken: CancelTokenStatic;
   Axios: typeof Axios;

test/typescript/axios.ts

@@ -263,6 +263,11 @@ instance1.defaults.headers.common['Authorization'] = 'token';
 instance1.defaults.headers.post['X-FOO'] = 'bar';
 instance1.defaults.timeout = 2500;
 
+// axios create defaults
+
+axios.create({ headers: { foo: 'bar' } });
+axios.create({ headers: { common: { foo: 'bar' } } });
+
 // Interceptors
 
 const requestInterceptorId: number = axios.interceptors.request.use(