Add WebDAV lifecycle UI feedback

main.go

@@ -465,9 +465,9 @@ func (u *ui) describeActionError(label string, err error) string {
 		return ""
 	}
 	if errors.Is(err, webdav.ErrConflict) || strings.Contains(err.Error(), webdav.ErrConflict.Error()) {
-		return "Save conflict: the remote vault changed. Reopen it and retry the save."
+		return fmt.Sprintf("%s failed: remote vault changed on the server; reopen the remote vault and retry", label)
 	}
-	return err.Error()
+	return fmt.Sprintf("%s failed: %v", label, err)
 }
 
 func (u *ui) bannerSurface() uiBanner {
@@ -728,6 +728,8 @@ func (u *ui) header(gtx layout.Context) layout.Dimensions {
 				}),
 				layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
 				layout.Rigid(u.lifecycleControls),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
+				layout.Rigid(u.feedbackBanner),
 			)
 		})
 	}
@@ -758,6 +760,8 @@ func (u *ui) header(gtx layout.Context) layout.Dimensions {
 			}),
 			layout.Rigid(layout.Spacer{Height: unit.Dp(10)}.Layout),
 			layout.Rigid(u.lifecycleControls),
+			layout.Rigid(layout.Spacer{Height: unit.Dp(10)}.Layout),
+			layout.Rigid(u.feedbackBanner),
 		)
 	})
 }
@@ -1295,6 +1299,27 @@ func detailLine(th *material.Theme, label, value string) layout.Widget {
 	}
 }
 
+func (u *ui) feedbackBanner(gtx layout.Context) layout.Dimensions {
+	message := u.statusMessage
+	tone := color.NRGBA{R: 231, G: 239, B: 235, A: 255}
+	textColor := accentColor
+	if u.errorMessage != "" {
+		message = u.errorMessage
+		tone = color.NRGBA{R: 248, G: 226, B: 223, A: 255}
+		textColor = color.NRGBA{R: 140, G: 46, B: 34, A: 255}
+	}
+	if message == "" {
+		return layout.Dimensions{}
+	}
+	return layout.Background{}.Layout(gtx, fill(tone), func(gtx layout.Context) layout.Dimensions {
+		return layout.UniformInset(unit.Dp(10)).Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+			lbl := material.Label(u.theme, unit.Sp(13), message)
+			lbl.Color = textColor
+			return lbl.Layout(gtx)
+		})
+	})
+}
+
 func (u *ui) passwordLine(label, value string) layout.Widget {
 	return func(gtx layout.Context) layout.Dimensions {
 		icon := u.eyeIcon

main_test.go

@@ -478,6 +478,99 @@ func TestUIOpenRemoteAndSaveThroughConfiguredWebDAVTarget(t *testing.T) {
 	}
 }
 
+func TestUIOpenRemoteReportsTransportFailure(t *testing.T) {
+	t.Parallel()
+
+	server := httptest.NewServer(http.HandlerFunc(func(http.ResponseWriter, *http.Request) {}))
+	url := server.URL
+	server.Close()
+
+	u := newUIWithSession("desktop", &session.Manager{})
+	u.masterPassword.SetText("correct horse battery staple")
+	u.remoteBaseURL.SetText(url)
+	u.remotePath.SetText("vaults/main.kdbx")
+
+	u.runAction("open remote vault", u.openRemoteAction)
+
+	if got := u.errorMessage; !strings.Contains(got, "open remote vault failed:") {
+		t.Fatalf("errorMessage = %q, want open remote vault failure", got)
+	}
+	if got := u.statusMessage; got != "" {
+		t.Fatalf("statusMessage = %q, want empty on remote open failure", got)
+	}
+}
+
+func TestUIRemoteSaveConflictShowsVisibleErrorAndKeepsDirtyState(t *testing.T) {
+	t.Parallel()
+
+	key := vault.MasterKey{Password: "correct horse battery staple"}
+	model := vault.Model{
+		Entries: []vault.Entry{
+			{
+				ID:       "vault-console",
+				Title:    "Vault Console",
+				Username: "dannyocean",
+				Password: "token-1",
+				URL:      "https://vault.crew.example.invalid",
+				Path:     []string{"Root", "Internet"},
+			},
+		},
+	}
+
+	var putCount int
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			var encoded bytes.Buffer
+			if err := vault.SaveKDBXWithKey(&encoded, model, key); err != nil {
+				t.Fatalf("SaveKDBXWithKey() error = %v", err)
+			}
+			w.Header().Set("ETag", "\"v1\"")
+			_, _ = w.Write(encoded.Bytes())
+		case http.MethodPut:
+			putCount++
+			w.WriteHeader(http.StatusPreconditionFailed)
+		default:
+			t.Fatalf("unexpected method %s", r.Method)
+		}
+	}))
+	defer server.Close()
+
+	u := newUIWithSession("desktop", &session.Manager{})
+	u.masterPassword.SetText("correct horse battery staple")
+	u.remoteBaseURL.SetText(server.URL)
+	u.remotePath.SetText("vaults/main.kdbx")
+
+	if err := u.openRemoteAction(); err != nil {
+		t.Fatalf("openRemoteAction() error = %v", err)
+	}
+	if err := u.state.UpsertEntry(vault.Entry{
+		ID:       "vault-console",
+		Title:    "Vault Console",
+		Username: "dannyocean",
+		Password: "token-2",
+		URL:      "https://vault.crew.example.invalid",
+		Path:     []string{"Root", "Internet"},
+	}); err != nil {
+		t.Fatalf("UpsertEntry() error = %v", err)
+	}
+
+	u.runAction("save vault", u.saveAction)
+
+	if got := u.errorMessage; !strings.Contains(got, "remote vault changed on the server") {
+		t.Fatalf("errorMessage = %q, want visible remote conflict guidance", got)
+	}
+	if got := u.statusMessage; got != "" {
+		t.Fatalf("statusMessage = %q, want empty after remote save conflict", got)
+	}
+	if !u.state.Dirty {
+		t.Fatal("Dirty = false, want true after remote save conflict")
+	}
+	if putCount != 1 {
+		t.Fatalf("remote PUT count = %d, want 1", putCount)
+	}
+}
+
 func TestUIMasterKeyInputSupportsKeyFileAndCompositeKeys(t *testing.T) {
 	t.Parallel()