Fix layout persistence issues in dashboard builder

[philippjfr]

Fixes issues with layout persistence ensuring that the temporary .layout file takes precedence over the notebook metadata.

[codecov]

Codecov Report

Attention: Patch coverage is 14.28571% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 82.96%. Comparing base (2a35d9c) to head (e90cc1a).

Files	Patch %	Lines
panel/io/handlers.py	0.00%	9 Missing ⚠️
panel/pane/vega.py	10.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6602      +/-   ##
==========================================
- Coverage   82.98%   82.96%   -0.03%     
==========================================
  Files         313      313              
  Lines       46073    46090      +17     
==========================================
+ Hits        38235    38239       +4     
- Misses       7838     7851      +13     

Flag	Coverage Δ
ui-tests	40.03% <4.76%> (-0.02%)	⬇️
unitexamples-tests	71.25% <14.28%> (-0.02%)	⬇️

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[MarcSkovMadsen]

I've

• created a new python environment and activated it
• pip installed jupyterlab param bokeh and matplotlib in it
• installed the branch pip install -e .
• started jupyter lab
• created a new notebook (not named or saved it, but it has been autosaved)

If I save it, its the same.

Its the same with an empty notebook.

I don't see issues in the terminal except the 404

$ jupyter lab
[I 2024-03-28 17:43:00.754 ServerApp] jupyter_lsp | extension was successfully linked.
[I 2024-03-28 17:43:00.767 ServerApp] jupyter_server_terminals | extension was successfully linked.
[I 2024-03-28 17:43:00.781 ServerApp] jupyterlab | extension was successfully linked.
[I 2024-03-28 17:43:01.405 ServerApp] notebook_shim | extension was successfully linked.
[I 2024-03-28 17:43:01.784 ServerApp] notebook_shim | extension was successfully loaded.
[I 2024-03-28 17:43:01.787 ServerApp] jupyter_lsp | extension was successfully loaded.
[I 2024-03-28 17:43:01.788 ServerApp] jupyter_server_terminals | extension was successfully loaded.
[I 2024-03-28 17:43:01.794 LabApp] JupyterLab extension loaded from C:\repos\private\panel\.venv\Lib\site-packages\jupyterlab
[I 2024-03-28 17:43:01.795 LabApp] JupyterLab application directory is C:\repos\private\panel\.venv\share\jupyter\lab
[I 2024-03-28 17:43:01.796 LabApp] Extension Manager is 'pypi'.
[I 2024-03-28 17:43:01.813 ServerApp] jupyterlab | extension was successfully loaded.
[I 2024-03-28 17:43:01.815 ServerApp] Serving notebooks from local directory: C:\repos\private\panel
[I 2024-03-28 17:43:01.816 ServerApp] Jupyter Server 2.13.0 is running at:
[I 2024-03-28 17:43:01.816 ServerApp] http://localhost:8888/lab?token=a9be9dc3cb276f310c0875205d565b90c9b0bf8beb182250
[I 2024-03-28 17:43:01.816 ServerApp]     http://127.0.0.1:8888/lab?token=a9be9dc3cb276f310c0875205d565b90c9b0bf8beb182250
[I 2024-03-28 17:43:01.817 ServerApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 2024-03-28 17:43:02.656 ServerApp] 

    To access the server, open this file in a browser:
        file:///C:/Users/masma/AppData/Roaming/jupyter/runtime/jpserver-25800-open.html
    Or copy and paste one of these URLs:
        http://localhost:8888/lab?token=a9be9dc3cb276f310c0875205d565b90c9b0bf8beb182250
        http://127.0.0.1:8888/lab?token=a9be9dc3cb276f310c0875205d565b90c9b0bf8beb182250
[W 2024-03-28 17:43:05.234 ServerApp] 404 GET /panel-preview/render/Demo.ipynb (8c45fd3456214736895113582b6526b4@127.0.0.1) 142.03ms referer=http://127.0.0.1:8888/panel-preview/render/Demo.ipynb
[I 2024-03-28 17:43:05.624 ServerApp] Skipped non-installed server(s): bash-language-server, dockerfile-language-server-nodejs, javascript-typescript-langserver, jedi-language-server, julia-language-server, pyright, python-language-server, python-lsp-server, r-languageserver, sql-language-server, texlab, typescript-language-server, unified-language-server, vscode-css-languageserver-bin, vscode-html-languageserver-bin, vscode-json-languageserver-bin, yaml-language-server
[I 2024-03-28 17:43:08.975 LabApp] Build is up to date
[I 2024-03-28 17:43:15.747 LabApp] Build is up to date
[I 2024-03-28 17:43:20.020 ServerApp] Kernel started: 67aeb99a-d19c-4924-81a7-c3fdc290fae1
[W 2024-03-28 17:43:20.959 ServerApp] 404 GET /panel-preview/layout/Demo.ipynb?1711644200956 (605b369e4a144d579ebb6b84cec229dc@::1) 2.00ms referer=http://localhost:8888/lab/workspaces/auto-I/tree/Demo.ipynb
[I 2024-03-28 17:43:20.973 ServerApp] Saving file at /Demo.ipynb
[W 2024-03-28 17:43:21.097 ServerApp] 404 GET /panel-preview/render/Demo.ipynb (605b369e4a144d579ebb6b84cec229dc@::1) 1.00ms referer=None
[I 2024-03-28 17:43:22.077 ServerApp] Connecting to kernel 67aeb99a-d19c-4924-81a7-c3fdc290fae1.
[I 2024-03-28 17:43:22.104 ServerApp] Connecting to kernel 67aeb99a-d19c-4924-81a7-c3fdc290fae1.
[I 2024-03-28 17:43:22.121 ServerApp] Connecting to kernel 67aeb99a-d19c-4924-81a7-c3fdc290fae1.
[W 2024-03-28 17:43:22.199 ServerApp] Got events for closed stream <zmq.eventloop.zmqstream.ZMQStream object at 0x00000246C1DFCE50>
[W 2024-03-28 17:43:22.209 ServerApp] Got events for closed stream <zmq.eventloop.zmqstream.ZMQStream object at 0x00000246C329A3D0>

[MarcSkovMadsen]

I should be able to use the preview correctly before merging.

[philippjfr]

That's really unrelated to what's being done in this PR. In a development install is different from a package install, so you may have to run:

jupyter serverextension enable panel.io.jupyter_server_extension

[philippjfr]

I'll just cut a dev release for you.