Transparently decompress gzip formatted response bodies

pkg/proxy/gzip.go

@@ -0,0 +1,35 @@
+package proxy
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+func gunzipResponseBody(res *http.Response) error {
+	if res.Header.Get("Content-Encoding") != "gzip" {
+		return nil
+	}
+
+	gzipReader, err := gzip.NewReader(res.Body)
+	if err != nil {
+		return fmt.Errorf("proxy: could not create gzip reader: %w", err)
+	}
+	defer gzipReader.Close()
+
+	buf := &bytes.Buffer{}
+
+	//nolint:gosec
+	if _, err := io.Copy(buf, gzipReader); err != nil {
+		return fmt.Errorf("proxy: could not read gzipped response body: %w", err)
+	}
+
+	res.Body = io.NopCloser(buf)
+	res.Header.Del("Content-Encoding")
+	res.Header.Set("Content-Length", fmt.Sprint(buf.Len()))
+	res.ContentLength = int64(buf.Len())
+
+	return nil
+}

pkg/proxy/proxy.go

@@ -114,6 +114,11 @@ func (p *Proxy) modifyRequest(r *http.Request) {
 func (p *Proxy) modifyResponse(res *http.Response) error {
 	fn := nopResModifier
 
+	// TODO: Make decompressing gzip formatted response bodies a configurable project setting.
+	if err := gunzipResponseBody(res); err != nil {
+		return fmt.Errorf("proxy: failed to gunzip response body: %w", err)
+	}
+
 	for i := len(p.resModifiers) - 1; i >= 0; i-- {
 		fn = p.resModifiers[i](fn)
 	}