fix(listen): join the forwarding URL path and the event path with a single slash

pkg/listen/proxy/forward_path_test.go

@@ -0,0 +1,62 @@
+package proxy
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/hookdeck/hookdeck-cli/pkg/websocket"
+)
+
+func TestProcessAttemptJoinsForwardingURLPathAndEventPath(t *testing.T) {
+	tests := []struct {
+		name       string
+		forwardTo  string
+		eventPath  string
+		expectPath string
+	}{
+		{"forwarding URL with a trailing slash", "/base/", "/webhook", "/base/webhook"},
+		{"forwarding URL without a trailing slash", "/base", "/webhook", "/base/webhook"},
+		{"forwarding URL is the root", "/", "/webhook", "/webhook"},
+		{"forwarding URL has no path", "", "/webhook", "/webhook"},
+		{"event path keeps its own trailing slash", "/base/", "/webhook/", "/base/webhook/"},
+		{"event path is empty", "/base/", "", "/base/"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			received := make(chan string, 1)
+			local := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				received <- r.URL.Path
+				w.WriteHeader(http.StatusOK)
+			}))
+			t.Cleanup(local.Close)
+
+			target, err := url.Parse(local.URL + tt.forwardTo)
+			require.NoError(t, err)
+			p := New(&Config{URL: target, NoHealthcheck: true}, nil, newRecordingRenderer())
+
+			p.processAttempt(websocket.IncomingMessage{Attempt: &websocket.Attempt{
+				Body: websocket.AttemptBody{
+					Path:      tt.eventPath,
+					EventID:   "evt_test",
+					AttemptId: "evt_test",
+					Request:   websocket.AttemptRequest{Method: http.MethodPost, DataString: "{}", Headers: json.RawMessage(`{}`)},
+				},
+			}})
+
+			select {
+			case got := <-received:
+				assert.Equal(t, tt.expectPath, got)
+			case <-time.After(5 * time.Second):
+				t.Fatal("local server never received the request")
+			}
+		})
+	}
+}

pkg/listen/proxy/proxy.go

@@ -14,6 +14,7 @@ import (
 	"os"
 	"os/signal"
 	"strconv"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"syscall"
@@ -379,6 +380,16 @@ func (p *Proxy) createSession(ctx context.Context) (hookdeck.Session, error) {
 	return session, err
 }
 
+// joinForwardPath appends the event's path to the forwarding URL's path with a
+// single "/" between them. A trailing "/" on the forwarding URL is dropped only
+// when the event path starts with one, and the event path itself is left as is.
+func joinForwardPath(base, eventPath string) string {
+	if strings.HasPrefix(eventPath, "/") {
+		base = strings.TrimSuffix(base, "/")
+	}
+	return base + eventPath
+}
+
 func (p *Proxy) processAttempt(msg websocket.IncomingMessage) {
 	if msg.Attempt == nil {
 		p.cfg.Log.Debug("WebSocket specified for Events received unexpected event")
@@ -392,7 +403,7 @@ func (p *Proxy) processAttempt(msg websocket.IncomingMessage) {
 		"prefix": "proxy.Proxy.processAttempt",
 	}).Debugf("Processing webhook event")
 
-	url := p.cfg.URL.Scheme + "://" + p.cfg.URL.Host + p.cfg.URL.Path + webhookEvent.Body.Path
+	url := p.cfg.URL.Scheme + "://" + p.cfg.URL.Host + joinForwardPath(p.cfg.URL.Path, webhookEvent.Body.Path)
 
 	// Create request with context for timeout control
 	timeout := webhookEvent.Body.Request.Timeout