From 2a892a3a2208aac5cef60e1180ed873bb10d43e0 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <prudiger@anaconda.com>
Date: Sat, 20 Jan 2024 23:27:06 +0100
Subject: [PATCH] Ensure ReactiveHTML correctly resets Event parameters (#6247)

* Ensure ReactiveHTML correctly resets Event parameters

* Add test

* Further fixes

* Update test
---
 panel/models/reactive_html.py   |  2 ++
 panel/models/reactive_html.ts   |  8 +++++++-
 panel/reactive.py               | 13 ++++++++++---
 panel/tests/ui/test_reactive.py | 27 ++++++++++++++++++++++++++-
 4 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/panel/models/reactive_html.py b/panel/models/reactive_html.py
index 9406635f93..e48678838d 100644
--- a/panel/models/reactive_html.py
+++ b/panel/models/reactive_html.py
@@ -231,6 +231,8 @@ class ReactiveHTML(HTMLBox):
 
     events = bp.Dict(bp.String, bp.Dict(bp.String, bp.Bool))
 
+    event_params = bp.List(bp.String)
+
     html = bp.String()
 
     looped = bp.List(bp.String)
diff --git a/panel/models/reactive_html.ts b/panel/models/reactive_html.ts
index c328f120ba..61b690f820 100644
--- a/panel/models/reactive_html.ts
+++ b/panel/models/reactive_html.ts
@@ -169,9 +169,13 @@ export class ReactiveHTMLView extends HTMLBoxView {
         const property = data_model.properties[attr]
         if (property == null)
           continue
+	const is_event_param = this.model.event_params.includes(prop)
         this.connect(property.change, () => {
-          if (!this._changing)
+          if (!this._changing && !(is_event_param && !data_model[prop])) {
             this.run_script(prop)
+	    if (is_event_param)
+	      data_model.setv({[prop]: false})
+	  }
         })
       }
     }
@@ -503,6 +507,7 @@ export namespace ReactiveHTML {
     callbacks: p.Property<any>
     children: p.Property<any>
     data: p.Property<any>
+    event_params: p.Property<string[]>
     events: p.Property<any>
     html: p.Property<string>
     looped: p.Property<string[]>
@@ -529,6 +534,7 @@ export class ReactiveHTML extends HTMLBox {
       callbacks: [ Any,    {} ],
       children:  [ Any,    {} ],
       data:      [ Any,       ],
+      event_params: [ Array(String), [] ],
       events:    [ Any,    {} ],
       html:      [ String, "" ],
       looped:    [ Array(String), [] ],
diff --git a/panel/reactive.py b/panel/reactive.py
index d71fe24eb5..173aaad8f9 100644
--- a/panel/reactive.py
+++ b/panel/reactive.py
@@ -1669,23 +1669,27 @@ def _init_params(self) -> Dict[str, Any]:
             p : getattr(self, p) for p in list(Layoutable.param)
             if getattr(self, p) is not None and p != 'name'
         }
-        data_params = {}
+        data_params, event_params = {}, []
         for k, v in self.param.values().items():
+            pobj = self.param[k]
             if (
                 (k in ignored and k != 'name') or
-                ((self.param[k].precedence or 0) < 0) or
-                (isinstance(v, Viewable) and not isinstance(self.param[k], param.ClassSelector))
+                ((pobj.precedence or 0) < 0) or
+                (isinstance(v, Viewable) and not isinstance(pobj, param.ClassSelector))
             ):
                 continue
             if isinstance(v, str):
                 v = HTML_SANITIZER.clean(v)
             data_params[k] = v
+            if isinstance(pobj, param.Event):
+                event_params.append(k)
         html, nodes, self._attrs = self._get_template()
         params.update({
             'attrs': self._attrs,
             'callbacks': self._node_callbacks,
             'data': self._data_model(**self._process_param_change(data_params)),
             'events': self._get_events(),
+            'event_params': event_params,
             'html': escape(textwrap.dedent(html)),
             'nodes': nodes,
             'looped': [node for node, _ in self._parser.looped],
@@ -1994,6 +1998,9 @@ def _update_model(
             model_msg['children'] = children
         self._set_on_model(model_msg, root, model)
         self._set_on_model(data_msg, root, model.data)
+        reset = {p: False for p in data_msg if p in model.event_params}
+        if reset:
+            self._set_on_model(reset, root, model.data)
 
     def on_event(self, node: str, event: str, callback: Callable) -> None:
         """
diff --git a/panel/tests/ui/test_reactive.py b/panel/tests/ui/test_reactive.py
index 6f1e6407c8..d64ad6906c 100644
--- a/panel/tests/ui/test_reactive.py
+++ b/panel/tests/ui/test_reactive.py
@@ -15,13 +15,16 @@ class ReactiveComponent(ReactiveHTML):
 
     count = param.Integer(default=0)
 
+    event = param.Event()
+
     _template = """
     <div id="reactive" class="reactive" onclick="${script('click')}"></div>
     """
 
     _scripts = {
         'render': 'data.count += 1; reactive.innerText = `${data.count}`;',
-        'click': 'data.count += 1; reactive.innerText = `${data.count}`;'
+        'click': 'data.count += 1; reactive.innerText = `${data.count}`;',
+        'event': 'data.count += 1; reactive.innerText = `${data.count}`;',
     }
 
 class ReactiveLiteral(ReactiveHTML):
@@ -46,6 +49,28 @@ def test_reactive_html_click_js_event(page):
 
     wait_until(lambda: component.count == 2, page)
 
+def test_reactive_html_param_event(page):
+    component = ReactiveComponent()
+
+    serve_component(page, component)
+
+    expect(page.locator(".reactive")).to_have_text('1')
+
+    component.param.trigger('event')
+
+    expect(page.locator(".reactive")).to_have_text('2')
+
+    component.param.trigger('event')
+
+    expect(page.locator(".reactive")).to_have_text('3')
+
+    component.param.trigger('event')
+    component.param.trigger('event')
+
+    expect(page.locator(".reactive")).to_have_text('5')
+
+    wait_until(lambda: component.count == 5, page)
+
 def test_reactive_html_set_loading_no_rerender(page):
     component = ReactiveComponent()