Adding custom plugin does not load in future sessions after first use of plugin.

[slothoth]

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Describe the bug
A clear and concise description of what the bug is.
When developing new plugins on Windows, there is a fault where the plugin can only load the first time when rebooting draw.io.
To Reproduce
Steps to reproduce the behavior:

1. Make a js test plugin with this code:

Draw.loadPlugin(function(ui) {
    console.log('Plugin initialized');
}

2. Load the plugin by going to Extras>Plugins>Add>External Plugins>Select File and choose your file
3. Close and relaunch drawio, making a new blank diagram. Check Help>DeveloperTools>Console and see the log message works
4. Close and relaunch drawio a second time, making a new blank diagram. Check Help>DeveloperTools>Console and see the log message is not present, and so the plugin has not loaded. Open Extras>Plugins to see the plugin still shows as listed.

Expected behavior
A plugin that is added and says it is loaded in the dialog persists across sessions.

Screenshots
If applicable, add screenshots to help explain your problem.

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version v26.0.9

Desktop (please complete the following information):

• OS: Windows 10

Additional context
Add any other context about the problem here.
Done using a fresh install with default settings, beyond running with the --enable-plugins argument

[rqdmap]

I encountered the same problem. I am using a Linux system, and this issue occurs in both draw.io version v26.0.9 and the latest version v26.0.16.

[davidjgraph]

which binary?

[rqdmap]

which binary?

I'm using Arch Linux, which appears to have compiled and packaged from the v26.0.9 source code. However, I also tested the drawio-x86_64-26.0.16.AppImage binary executable from the releases page, and it exhibits the same plugin loading issue.

[ThomasOphe]

I'm still having this issue on version V27.0.9, plugin only loads once after restarting and after that it won't load.
Using MacOS

[thebeav26]

I'm seeing this same issue with v28.0.6.

If I run the desktop version of draw.io from a terminal with the --enable-plugins flag, I can successfully add my plugin (extras --> plugins, add -> external plugins (select file). And it works as expected the first time after restarting draw.io (again using the --enable-plugins flag from terminal). But if I exit the application and again run with the --enable-plugins flag, the plugin no longer works. However, the file path (starting with file://C:\Users) does show up under extras --> plugins

[iurifarenzena]

My previous comment got delete, I don't know why, but let me apologize in advance in case this one is also not allowed.

I was able to get the desktop plugins loading correctly after several restarts of the app with a change in the getPluginFile function in electron.js file.
Basically the function is receiving the complete file path and then it tries to concatenate it with the base plugins folder, resulting in an invalid file name.
The solution was to extract only the file name from the input path before combining it with the prefix.
I know the repo is not open for contributions, but I'll leave here the commit 5589e1f in case it makes someone else's life easier.

Again, if this comment has any issues, please let me know why instead of just deleting it.

[davidjgraph]

It got deleted because your comment was "me too", it added nothing but noise to the thread.