Remove PreferencesUtils#readPrefsFromJS due to Nashorn removal

[Don-vip]

Or simply drop it. It's here since :ticket:4421#comment:34 but I don't think it's being used much. We should ask on @josm-dev

[simon04]

​https://lists.openstreetmap.org/pipermail/josm-dev/2020-March/008285.html

…
Nashorn was in use for three features of JOSM core:
…

3. JavaScript API of JOSM configuration XML files, Help/Preferences/ImportExport#JavaScriptAPI

…
… we don't see a viable alternative. We plan to remove this

feature with the next JOSM release unless someone steps up with a
killer-user-case and migration plan

[Don-vip]

I also reported it there:
​https://www.openstreetmap.org/user/josmeditor/diary/392391
​https://twitter.com/josmeditor/status/1235662483777441792

[Don-vip]

Descoping to release 20.03 early to address #18798, as we receive a lot of duplicates, and to allow some time for feedback, even if I think nobody will show up.

[simon04]

Removing PreferencesUtils#readPrefsFromJS is the easy part. The ScriptEngine, however, is heavily used via CustomConfigurator.XMLCommandProcessor#evalVars in order to evaluate various strings/values, such as Help/Preferences/ImportExport#Variablesmessageboxesandaskinguser

What should we do?

1. Rewrite evalVars to only lookup variables, but not compute values?
2. Rewrite evalVars to mimic the most important computations (such as math and string computations)?
3. Rewrite evalVars to use MapCSS functions?
4. Use ​https://github.com/beanshell/beanshell or a similar library?
5. …?

[simon04]

Replying to simon04:

What should we do?

1. Rewrite evalVars to only lookup variables, but not compute values?

I chose this variant.

[simon04]

In 16329/josm:

fix #18830 - Remove PreferencesUtils#readPrefsFromJS due to Nashorn removal

[simon04]

In 16330/josm:

see #18830 - Remove Utils#getJavaScriptEngine due to Nashorn removal

[simon04]

Documentation: Help/Preferences/ImportExport?action=diff&version=11

[Klumbumbus]

Milestone renamed