Fix AttributeError when using Viewer, Parameterized, or arbitrary objects as node views

[Copilot]

• Understand the issue: views are not resolved like editors, causing Viewer objects to fail
• Apply the fix: use _resolve_editor_view for views in _get_children method
• Create test to validate Viewer objects work in nodes
• Add test for arbitrary objects (HoloViews, etc.) to validate issue Cannot use arbitrary python objects as view #13 is fixed
• Merge with updated main branch (comprehensive numpy-style docstrings)
• Fix pre-commit issues (code formatting and unused variables)
• Run all tests to ensure no regressions (30 passed, 2 skipped)
• All pre-commit checks pass

Summary

Fixed the issue where pn.viewable.Viewer objects, param.Parameterized objects, and arbitrary objects like HoloViews plots would raise AttributeError: 'MyViewer' object has no attribute '_models' when used as node views.

Successfully merged with main branch and resolved all pre-commit issues.

Changes Made

1. Modified /src/panel_reactflow/base.py: Changed line 1319 to apply _resolve_editor_view() to views, ensuring objects with __panel__() methods are properly resolved, and other objects are converted via pn.panel()
2. Added tests in /tests/test_api.py:
   • test_reactflow_add_node_with_viewer() - validates Viewer objects work correctly
   • test_reactflow_add_node_with_arbitrary_object() - validates arbitrary objects (e.g., HoloViews) work correctly (issue Cannot use arbitrary python objects as view #13)
3. Merged main branch: Incorporated comprehensive numpy-style docstrings from main branch
4. Fixed pre-commit issues: Applied ruff formatting and fixed unused variable warnings by using underscore prefix

Issues Fixed

• Original issue: Viewer and Parameterized objects as views
• Issue Cannot use arbitrary python objects as view #13: Arbitrary objects (HoloViews, matplotlib, etc.) as views

Security Summary

No security vulnerabilities found or introduced.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Viewer: AttributeError: 'MyViewer' object has no attribute '_models'</issue_title>
<issue_description>I cannot use Viewer components because they raise errors.

Reproduce

import panel as pn

from panel_reactflow import ReactFlow


class MyViewer(pn.viewable.Viewer):
    def __panel__(self):
        return pn.pane.Markdown("Hello React Flow!")


my_viewer = MyViewer()

nodes = [
    {
        "id": "source",
        "type": "panel",
        "label": "Data Source",
        "position": {"x": 0, "y": 0},
        "data": {},
        "view": my_viewer,
    },
]

ReactFlow(nodes=nodes, edges=[], sizing_mode="stretch_both").servable()

AttributeError: 'MyViewer' object has no attribute '_models'

Traceback (most recent call last):
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/io/handlers.py", line 539, in run
    exec(self._code, module.__dict__)
    ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jovyan/repos/private/panel-reactflow/script.py", line 24, in <module>
    ReactFlow(nodes=nodes, edges=[], sizing_mode="stretch_both").servable()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/viewable.py", line 417, in servable
    self.server_doc(doc, title=title, location=location) # type: ignore
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/viewable.py", line 1044, in server_doc
    model = self.get_root(doc)
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/viewable.py", line 706, in get_root
    root = self._get_model(doc, comm=comm)
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/custom.py", line 567, in _get_model
    children, _ = self._get_children(model.data, doc, root, model, comm)
                  ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jovyan/repos/private/panel-reactflow/src/panel_reactflow/base.py", line 642, in _get_children
    views, view_models = self._get_child_model(views, doc, root, parent, comm)
                         ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jovyan/repos/private/panel-reactflow/.pixi/envs/default/lib/python3.14/site-packages/panel/custom.py", line 525, in _get_child_model
    if ref in sv._models:
              ^^^^^^^^^^
AttributeError: 'MyViewer' object has no attribute '_models'
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
<comment_new><author>@MarcSkovMadsen</author><body>
The same problem if I provide a param.Parameter as the view on a node.</body></comment_new>
</comments>

• Fixes Viewer: AttributeError: 'MyViewer' object has no attribute '_models' #12

---

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[MarcSkovMadsen]

@copilot . Please fix #13 in this PR too.

[Copilot]

@copilot . Please fix #13 in this PR too.

Issue #13 is now fixed. The existing fix already handles arbitrary objects (like HoloViews plots) by calling pn.panel() on them. Added test test_reactflow_add_node_with_arbitrary_object() to validate this works correctly. See commit 9ee68a4.

[MarcSkovMadsen]

Please merge with updated main and fix any issues. Including docstring issues as docstrings have been significantly improved.

[Copilot]

Please merge with updated main and fix any issues. Including docstring issues as docstrings have been significantly improved.

Merged with updated main branch successfully. All tests pass (30 passed, 2 skipped). The fix remains intact after merge with comprehensive numpy-style docstrings from main. See merge commit 1cb514f.

[MarcSkovMadsen]

Please fix pre-commit issues

[Copilot]

Please fix pre-commit issues

Pre-commit issues fixed. Applied ruff formatting and resolved unused variable warnings. All pre-commit checks now pass. See commit 5004f21.