Added custom params serializer support;

index.d.ts

@@ -247,8 +247,13 @@ export interface ParamEncoder {
   (value: any, defaultEncoder: (value: any) => any): any;
 }
 
+export interface CustomParamsSerializer {
+  (params: object, options?: ParamsSerializerOptions): string;
+}
+
 export interface ParamsSerializerOptions extends SerializerOptions {
   encode?: ParamEncoder;
+  serialize?: CustomParamsSerializer;
 }
 
 type MaxUploadRate = number;

lib/core/Axios.js

@@ -47,7 +47,7 @@ class Axios {
 
     config = mergeConfig(this.defaults, config);
 
-    const transitional = config.transitional;
+    const {transitional, paramsSerializer} = config;
 
     if (transitional !== undefined) {
       validator.assertOptions(transitional, {
@@ -57,6 +57,13 @@ class Axios {
       }, false);
     }
 
+    if (paramsSerializer !== undefined) {
+      validator.assertOptions(paramsSerializer, {
+        encode: validators.function,
+        serialize: validators.function
+      }, false)
+    }
+
     // Set config.method
     config.method = (config.method || this.defaults.method || 'get').toLowerCase();
 

lib/helpers/buildURL.js

@@ -44,12 +44,20 @@ export default function buildURL(url, params, options) {
 
   const _encode = options && options.encode || encode;
 
-  const serializerParams = utils.isURLSearchParams(params) ?
-    params.toString() :
-    new AxiosURLSearchParams(params, options).toString(_encode);
+  const serializeFn = options && options.serialize;
 
-  if (serializerParams) {
-    url += (url.indexOf('?') === -1 ? '?' : '&') + serializerParams;
+  let serializedParams;
+
+  if (serializeFn) {
+    serializedParams = serializeFn(params, options);
+  } else {
+    serializedParams = utils.isURLSearchParams(params) ?
+      params.toString() :
+      new AxiosURLSearchParams(params, options).toString(_encode);
+  }
+
+  if (serializedParams) {
+    url += (url.indexOf('?') === -1 ? '?' : '&') + serializedParams;
   }
 
   return url;

test/specs/helpers/buildURL.spec.js

@@ -63,4 +63,20 @@ describe('helpers::buildURL', function () {
   it('should support URLSearchParams', function () {
     expect(buildURL('/foo', new URLSearchParams('bar=baz'))).toEqual('/foo?bar=baz');
   });
+
+  it('should support custom serialize function', function () {
+    const params = {
+      x: 1
+    }
+
+    const options = {
+      serialize: (thisParams, thisOptions) => {
+        expect(thisParams).toEqual(params);
+        expect(thisOptions).toEqual(options);
+        return "rendered"
+      }
+    };
+
+    expect(buildURL('/foo', params, options)).toEqual('/foo?rendered');
+  });
 });

test/typescript/axios.ts

@@ -21,7 +21,8 @@ const config: AxiosRequestConfig = {
   params: { id: 12345 },
   paramsSerializer: {
     indexes: true,
-    encode: (value) => value
+    encode: (value) => value,
+    serialize: (value, options) => String(value)
   },
   data: { foo: 'bar' },
   timeout: 10000,