Can't set javadoc of Android Dependencies libraries

If you add a jar in libs folder, it's automatically add in the Android Dependencies.
Great no ? nothing else to do !

 Ok, now try to add javadoc and source attachment like usual...
Project Properties > Java Build Path > Libraries then Android Dependencies > mylib.jar ....
errr... wait a minute...non modifiable
WTF ?!
you can't set doc and source of an auto linked library.

After some googling/stackoverflowing I finally found the answer

To summarize, you should add a mylib.jar.properties file
In this file write 2 lines :

src=<path to mylib-sources.jar>
doc=<path to mylib-javadoc.jar>

Hint : don't forget to close / reopen the project to update Android Dependencies

For Temporary Mail, my libs folder is now

and so Android Dependencies is now filled

It's still non modifiable but I don't care : I have my source and doc while debugging !

Another hour lost trying to do something basic.