feat: add request funcs method for request composition (#910)

Co-authored-by: thinkgo <[email protected]>

client.go

@@ -97,6 +97,9 @@ type (
 	// SuccessHook type is for reacting to request success
 	SuccessHook func(*Client, *Response)
 
+	// RequestFunc type is for extended manipulation of the Request instance
+	RequestFunc func(*Request) *Request
+
 	// TLSClientConfiger interface is to configure TLS Client configuration on custom transport
 	// implemented using [http.RoundTripper]
 	TLSClientConfiger interface {

request.go

@@ -1437,6 +1437,33 @@ func (r *Request) Clone(ctx context.Context) *Request {
 	return rr
 }
 
+// Funcs method gets executed on request composition that passes the
+// current request instance to provided [RequestFunc], which could be
+// used to apply common/reusable logic to the given request instance.
+//
+//	func addRequestContentType(r *Request) *Request {
+//		return r.SetHeader("Content-Type", "application/json").
+//			SetHeader("Accept", "application/json")
+//	}
+//
+//	func addRequestQueryParams(page, size int) func(r *Request) *Request {
+//		return func(r *Request) *Request {
+//			return r.SetQueryParam("page", strconv.Itoa(page)).
+//				SetQueryParam("size", strconv.Itoa(size)).
+//				SetQueryParam("request_no", strconv.Itoa(int(time.Now().Unix())))
+//		}
+//	}
+//
+//	client.R().
+//		Funcs(addRequestContentType, addRequestQueryParams(1, 100)).
+//		Get("https://localhost:8080/foobar")
+func (r *Request) Funcs(funcs ...RequestFunc) *Request {
+	for _, f := range funcs {
+		r = f(r)
+	}
+	return r
+}
+
 func (r *Request) fmtBodyString(sl int) (body string) {
 	body = "***** NO CONTENT *****"
 	if !r.isPayloadSupported() {

request_test.go

@@ -2201,6 +2201,40 @@ func TestRequestSetResultAndSetOutputFile(t *testing.T) {
 	assertEqual(t, `{ "id": "success", "message": "login successful" }`, string(fileContent))
 }
 
+func TestRequestFuncs(t *testing.T) {
+	ts := createGetServer(t)
+	defer ts.Close()
+
+	c := dcnl().
+		SetQueryParam("client_param", "true").
+		SetQueryParams(map[string]string{"req_1": "value1", "req_3": "value3"}).
+		SetDebug(true)
+
+	addRequestQueryParams := func(page, size int) func(r *Request) *Request {
+		return func(r *Request) *Request {
+			return r.SetQueryParam("page", strconv.Itoa(page)).
+				SetQueryParam("size", strconv.Itoa(size)).
+				SetQueryParam("request_no", strconv.Itoa(int(time.Now().Unix())))
+		}
+	}
+
+	addRequestHeaders := func(r *Request) *Request {
+		return r.SetHeader(hdrAcceptKey, "application/json").
+			SetHeader(hdrUserAgentKey, "my-client/v1.0")
+	}
+
+	resp, err := c.R().
+		Funcs(addRequestQueryParams(1, 100), addRequestHeaders).
+		SetHeader(hdrUserAgentKey, "Test Custom User agent").
+		Get(ts.URL + "/")
+
+	assertError(t, err)
+	assertEqual(t, http.StatusOK, resp.StatusCode())
+	assertEqual(t, "HTTP/1.1", resp.Proto())
+	assertEqual(t, "200 OK", resp.Status())
+	assertEqual(t, "TestGet: text response", resp.String())
+}
+
 // This test methods exist for test coverage purpose
 // to validate the getter and setter
 func TestRequestSettingsCoverage(t *testing.T) {