fix: 🐛 cors issues

Author: GerardPolloRebozado

proxy.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"net/url"
-	"strings"
 )
 
 func NewReverseProxy(base string) (*httputil.ReverseProxy, error) {
@@ -18,7 +17,7 @@ func NewReverseProxy(base string) (*httputil.ReverseProxy, error) {
 	origDirector := proxy.Director
 	proxy.Director = func(req *http.Request) {
 		origDirector(req)
-		req.URL.Path = joinPath(target.Path, req.URL.Path)
+		// req.URL.Path is already updated by origDirector (singleJoiningSlash)
 		req.Header.Set("X-Forwarded-Host", req.Host)
 		if req.TLS != nil {
 			req.Header.Set("X-Forwarded-Proto", "https")
@@ -27,22 +26,19 @@ func NewReverseProxy(base string) (*httputil.ReverseProxy, error) {
 		}
 	}
 
+	proxy.ModifyResponse = func(resp *http.Response) error {
+		// Drop CORS headers from upstream to avoid duplicates with our middleware
+		resp.Header.Del("Access-Control-Allow-Origin")
+		resp.Header.Del("Access-Control-Allow-Methods")
+		resp.Header.Del("Access-Control-Allow-Headers")
+		resp.Header.Del("Access-Control-Expose-Headers")
+		return nil
+	}
+
 	proxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
 		log.Printf("proxy error for %s: %v", r.URL.String(), err)
 		http.Error(w, "Upstream error", http.StatusBadGateway)
 	}
 
 	return proxy, nil
-}
-
-func joinPath(a, b string) string {
-	aslash := strings.HasSuffix(a, "/")
-	bslash := strings.HasPrefix(b, "/")
-	switch {
-	case aslash && bslash:
-		return a + b[1:]
-	case !aslash && !bslash:
-		return a + "/" + b
-	}
-	return a + b
-}
+}