No it does not, and I didn't think it should since there was no test for this :/

Order should be preserved, but empty lines will definitly go away.
And a file header comment is automatically generated with generation date for the file (can't remove it, can only provide a default value on properties.store(outputStream, comment))

If those points are mandatory behaviours for the component, they should be tested accordingly beforehand

No it does not, and I didn't think it should since there was no test for this :/

Order should be preserved, but empty lines will definitly go away. And a file header comment is automatically generated with generation date for the file (can't remove it, can only provide a default value on properties.store(outputStream, comment))

If those points are mandatory behaviours for the component, they should be tested accordingly beforehand

For me they are, we learned that later on but I think this is really important. @pascalgrimaud any advice on this?

IMO these points are indeed mandatory.
We try to preserve as much as possible the existing source file, and the header will generate some additional noise in system versioning changes.

First step : adding tests to check those behaviours in existing class

• order in file preserved
• comment preserved
• white line preserved
• new key/values appended at the end of the file
• new values appended at the end of current existing values for key

Something like this :

(yes, it works on main branch even on my setup, be with a very ugly fix i'm too ashamed to show here)

This should go in another pull request/issue