🔥 feat: Add StreamResponseBody support for the Client

Author: Abhirup-99

client/client.go

@@ -526,6 +526,20 @@ func (c *Client) DisableDebug() *Client {
 	return c
 }
 
+// StreamResponseBody returns the current StreamResponseBody setting.
+func (c *Client) StreamResponseBody() bool {
+	return c.transport.StreamResponseBody()
+}
+
+// SetStreamResponseBody enables or disables response body streaming.
+// When enabled, the response body can be read as a stream using BodyStream()
+// instead of being fully loaded into memory. This is useful for large responses
+// or server-sent events.
+func (c *Client) SetStreamResponseBody(enable bool) *Client {
+	c.transport.SetStreamResponseBody(enable)
+	return c
+}
+
 // SetCookieJar sets the cookie jar for the client.
 func (c *Client) SetCookieJar(cookieJar *CookieJar) *Client {
 	c.cookieJar = cookieJar

client/client_test.go

@@ -2343,3 +2343,65 @@ func Benchmark_Client_Request_Send_ContextCancel(b *testing.B) {
 		require.ErrorIs(b, <-errCh, ErrTimeoutOrCancel)
 	}
 }
+
+func Test_Client_StreamResponseBody(t *testing.T) {
+	t.Parallel()
+
+	t.Run("default value", func(t *testing.T) {
+		t.Parallel()
+		client := New()
+		require.False(t, client.StreamResponseBody())
+	})
+
+	t.Run("enable streaming", func(t *testing.T) {
+		t.Parallel()
+		client := New()
+		result := client.SetStreamResponseBody(true)
+		require.True(t, client.StreamResponseBody())
+		require.Equal(t, client, result)
+	})
+
+	t.Run("disable streaming", func(t *testing.T) {
+		t.Parallel()
+		client := New()
+		client.SetStreamResponseBody(true)
+		require.True(t, client.StreamResponseBody())
+		client.SetStreamResponseBody(false)
+		require.False(t, client.StreamResponseBody())
+	})
+
+	t.Run("with standard client", func(t *testing.T) {
+		t.Parallel()
+		client := New()
+		client.SetStreamResponseBody(true)
+		require.True(t, client.StreamResponseBody())
+	})
+
+	t.Run("with host client", func(t *testing.T) {
+		t.Parallel()
+		hostClient := &fasthttp.HostClient{}
+		client := NewWithHostClient(hostClient)
+		client.SetStreamResponseBody(true)
+		require.True(t, client.StreamResponseBody())
+		require.True(t, hostClient.StreamResponseBody)
+	})
+
+	t.Run("with lb client", func(t *testing.T) {
+		t.Parallel()
+		lbClient := &fasthttp.LBClient{
+			Clients: []fasthttp.BalancingClient{
+				&fasthttp.HostClient{Addr: "example.com:80"},
+			},
+		}
+		client := NewWithLBClient(lbClient)
+		client.SetStreamResponseBody(true)
+		require.True(t, client.StreamResponseBody())
+	})
+
+	t.Run("getter with standard client without setter", func(t *testing.T) {
+		t.Parallel()
+		client := New()
+		// Test getter directly without calling setter
+		require.False(t, client.StreamResponseBody())
+	})
+}

client/core.go

@@ -86,9 +86,16 @@ func (c *core) execFunc() (*Response, error) {
 		defer fasthttp.ReleaseRequest(reqv)
 
 		respv := fasthttp.AcquireResponse()
-		defer fasthttp.ReleaseResponse(respv)
+		defer func() {
+			if respv != nil {
+				fasthttp.ReleaseResponse(respv)
+			}
+		}()
 
 		c.req.RawRequest.CopyTo(reqv)
+		if bodyStream := c.req.RawRequest.BodyStream(); bodyStream != nil {
+			reqv.SetBodyStream(bodyStream, c.req.RawRequest.Header.ContentLength())
+		}
 
 		var err error
 		if cfg != nil {
@@ -115,7 +122,12 @@ func (c *core) execFunc() (*Response, error) {
 		resp := AcquireResponse()
 		resp.setClient(c.client)
 		resp.setRequest(c.req)
-		respv.CopyTo(resp.RawResponse)
+		originalRaw := resp.RawResponse
+		resp.RawResponse = respv
+		respv = nil
+		if originalRaw != nil {
+			fasthttp.ReleaseResponse(originalRaw)
+		}
 		respChan <- resp
 	}()
 

client/core_test.go

@@ -383,6 +383,13 @@ func (*blockingErrTransport) Client() any {
 	return nil
 }
 
+func (*blockingErrTransport) StreamResponseBody() bool {
+	return false
+}
+
+func (*blockingErrTransport) SetStreamResponseBody(_ bool) {
+}
+
 func (b *blockingErrTransport) release() {
 	b.releaseOnce.Do(func() { close(b.unblock) })
 }

client/response.go

@@ -11,7 +11,7 @@ import (
 	"path/filepath"
 	"sync"
 
-	"github.com/gofiber/utils/v2"
+	utils "github.com/gofiber/utils/v2"
 	"github.com/valyala/fasthttp"
 )
 
@@ -89,22 +89,38 @@ func (r *Response) Body() []byte {
 	return r.RawResponse.Body()
 }
 
+// BodyStream returns the response body as a stream reader.
+// Note: When using BodyStream(), the response body is not copied to memory,
+// so calling Body() afterwards may return an empty slice.
+func (r *Response) BodyStream() io.Reader {
+	if stream := r.RawResponse.BodyStream(); stream != nil {
+		return stream
+	}
+	// If streaming is not enabled, return a bytes.Reader from the regular body
+	return bytes.NewReader(r.RawResponse.Body())
+}
+
+// IsStreaming returns true if the response body is being streamed.
+func (r *Response) IsStreaming() bool {
+	return r.RawResponse.BodyStream() != nil
+}
+
 // String returns the response body as a trimmed string.
 func (r *Response) String() string {
 	return utils.Trim(string(r.Body()), ' ')
 }
 
-// JSON unmarshal the response body into the given interface{} using JSON.
+// JSON unmarshals the response body into the given interface{} using JSON.
 func (r *Response) JSON(v any) error {
 	return r.client.jsonUnmarshal(r.Body(), v)
 }
 
-// CBOR unmarshal the response body into the given interface{} using CBOR.
+// CBOR unmarshals the response body into the given interface{} using CBOR.
 func (r *Response) CBOR(v any) error {
 	return r.client.cborUnmarshal(r.Body(), v)
 }
 
-// XML unmarshal the response body into the given interface{} using XML.
+// XML unmarshals the response body into the given interface{} using XML.
 func (r *Response) XML(v any) error {
 	return r.client.xmlUnmarshal(r.Body(), v)
 }
@@ -136,21 +152,30 @@ func (r *Response) Save(v any) error {
 		}
 		defer func() { _ = outFile.Close() }() //nolint:errcheck // not needed
 
-		if _, err = io.Copy(outFile, bytes.NewReader(r.Body())); err != nil {
+		if r.IsStreaming() {
+			_, err = io.Copy(outFile, r.BodyStream())
+		} else {
+			_, err = io.Copy(outFile, bytes.NewReader(r.Body()))
+		}
+
+		if err != nil {
 			return fmt.Errorf("failed to write response body to file: %w", err)
 		}
 
 		return nil
 
 	case io.Writer:
-		if _, err := io.Copy(p, bytes.NewReader(r.Body())); err != nil {
-			return fmt.Errorf("failed to write response body to io.Writer: %w", err)
+		var err error
+		if r.IsStreaming() {
+			_, err = io.Copy(p, r.BodyStream())
+		} else {
+			_, err = io.Copy(p, bytes.NewReader(r.Body()))
 		}
-		defer func() {
-			if pc, ok := p.(io.WriteCloser); ok {
-				_ = pc.Close() //nolint:errcheck // not needed
-			}
-		}()
+
+		if err != nil {
+			return fmt.Errorf("failed to write response body to writer: %w", err)
+		}
+
 		return nil
 
 	default: