Ensure ReactiveHTML inline callbacks on looped nodes return correct node

[philippjfr]

Ensures that in example like below the onclick event returns a DOMEvent with the node set to the runtime value (list-item-0) rather than the template value: list-item-{{ loop.index0 }}:

class Test(pn.reactive.ReactiveHTML):
    
    a = param.List()
    
    _template = """
    <div id="list">
    {% for item in a %}
      <div id="list-item-{{ loop.index0 }}" onclick=${_call}>${item}</div>
    {% endfor %}
    </div>"""
    
    def _call(self, event):
        print(event.node)

[codecov]

Codecov Report

Merging #3840 (0775d15) into master (affb9dd) will decrease coverage by 0.07%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #3840      +/-   ##
==========================================
- Coverage   82.86%   82.79%   -0.08%     
==========================================
  Files         222      222              
  Lines       32413    32415       +2     
==========================================
- Hits        26860    26837      -23     
- Misses       5553     5578      +25     

Flag	Coverage Δ
ui-tests	33.88% <0.00%> (-0.33%)	⬇️
unitexamples-tests	75.23% <0.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
panel/reactive.py	78.14% <0.00%> (-0.18%)	⬇️
panel/tests/ui/io/test_jupyter_server_extension.py	40.74% <0.00%> (-59.26%)	⬇️
panel/tests/util.py	85.14% <0.00%> (-1.99%)	⬇️
panel/tests/conftest.py	86.78% <0.00%> (-1.33%)	⬇️
panel/util.py	86.41% <0.00%> (-0.76%)	⬇️

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