I found out why it's not working and why it worked when there was a file in file history.

It has to do with the order of executions and the following lines of code

Here is a detailed explanation

The order of executions is as follows when debugging

1. create a new element library
   a. calls the LibraryNode.traverse() method from populateNodeMap()
   b. calls the LibraryNode.traverse() method directly
   

   Digital/src/main/java/de/neemann/digital/draw/library/ElementLibrary.java

   Lines 255 to 263 in 426a1e1

   	populateNodeMap();
   	isProgrammable.clear();
   	root.traverse(libraryNode -> {
   	ElementTypeDescription d = libraryNode.getDescriptionOrNull();
   	if (d != null && d.hasAttribute(Keys.BLOWN))
   	isProgrammable.add(d.getName());
   	});

2. register components from custom Java components to the above-created library using the ElementLibrary.registerComponentSource() method
3. set the above created and modified library as the library of MainBuilder using the MainBuilder.setLibrary() method
4. then the MainBuilder.openLater() method calls the MainBuilder.build() method which in turn instantiates the Main class
5. while instantiating the Main class, as per the first block of code linked, the LibraryNode.traverse() method is called once more as a result of calling the Main.loadFile() method which only happens if there is a file in File History

The gotcha

First two calls to the LibraryNode.traverse() method happens before the ElementLibrary.registerComponentSource() and the MainBuilder.setLibrary() method calls. Because of this, the custom Java components are not in the element library when the LibraryNode.traverse() method is called which is responsible for marking library nodes as unique. Since the custom Java components are not marked as unique, they become unusable. And since the LibraryNode.traverse() method is called once more after all this when there is a file in File History, the custom Java components become usable.

Originally posted by @me-nkr in #1312 (comment)

from digital.