Ensure FileDownload label text updates correctly (#7489)

panel/models/file_download.ts

@@ -38,6 +38,7 @@ export class FileDownloadView extends InputWidgetView {
 
   anchor_el: HTMLAnchorElement
   button_el: HTMLButtonElement
+  label_el: Text
   declare input_el: HTMLInputElement  // HACK: So this.input_el.id = "input" can be set in Bokeh 3.4
   _downloadable: boolean = false
   _click_listener: any
@@ -101,8 +102,9 @@ export class FileDownloadView extends InputWidgetView {
       this.anchor_el.appendChild(separator)
       this.icon_view.render()
     }
+    this.label_el = document.createTextNode(this.model.label)
+    this.anchor_el.appendChild(this.label_el)
     this._update_button_style()
-    this._update_label()
 
     // Changing the disabled property calls render() so it needs to be handled here.
     // This callback is inherited from ControlView in bokehjs.
@@ -201,8 +203,7 @@ export class FileDownloadView extends InputWidgetView {
   }
 
   _update_label(): void {
-    const label = document.createTextNode(this.model.label)
-    this.anchor_el.appendChild(label)
+    this.label_el.data = this.model.label
   }
 
   _update_button_style(): void {

panel/tests/ui/widgets/test_misc.py

@@ -5,6 +5,10 @@
 import param
 import pytest
 
+pytest.importorskip("playwright")
+
+from playwright.sync_api import expect
+
 from panel.layout import Column, Tabs
 from panel.tests.util import serve_component
 from panel.widgets import FileDownload, TextInput
@@ -13,6 +17,18 @@
 not_windows = pytest.mark.skipif(sys.platform=='win32', reason="Does not work on Windows")
 
 
+def test_file_download_label_updates(page):
+
+    download = FileDownload(filename='f.txt', embed=False, callback=lambda: io.StringIO())
+
+    serve_component(page, download)
+
+    expect(page.locator('.bk-btn a')).to_have_text('Download f.txt')
+
+    download.filename = 'g.txt'
+
+    expect(page.locator('.bk-btn a')).to_have_text('Download g.txt')
+
 @not_windows
 def test_file_download_updates_when_navigating_between_dynamic_tabs(page):
     text_input = TextInput(value='abc')