Add VS code extensions preferences in workspace configuration

[l0rd]

Description

For example it should be possible to override the default JDT LS vmargs to match the sidecar container memory settings. Today that's not possible and we have 2 workarounds that are not really satisfactory:

• use a sidecar with > 1.5GB (may be too much for che.openshift.io)
• start the workspace and edit the JTD LS vmargs from Theia settings (but the UX is awful)

That same problem will exist for any VS Code plugin that has some defaults that may not work well when they run in a container.

Here is a proposal to include that in a devfile and workspace.config:

  - name: java support
    type: chePlugin
    id: 'org.eclipse.che.vscode-redhat.java:0.38.0'
    preferences:
       java.jdt.ls.vmargs: '-noverify -Xmx1G -XX:+UseG1GC -XX:+UseStringDeduplication'
       java.home: '/home/user/jdk11'

devfile

and in json config

"attributes": {
  "plugin.org.eclipse.che.vscode-redhat.java.java.jdt.ls.vmargs": "-noverify -Xmx1G -XX:+UseG1GC -XX:+UseStringDeduplication",
  "plugin.org.eclipse.che.vscode-redhat.java.java.home": "/home/user/jdk11"
...
}

workspace config

[garagatyi]

@l0rd who should take these preferences from workspace config and incorporate them in Theia? Some Che-theia extension, right?

[l0rd]

@garagatyi I don't know what's the best way to implement that. We need some Theia specialists here cc @benoitf @evidolob @azatsarynnyy

[azatsarynnyy]

There's the Theia extension in Che Theia that is responsible for mapping/synchronizing the Theia Settings with the Che User Preferences. I think that extension suits perfect for performing such an additional job. E.g., on Theia start, the extension can look into the Che Workspace config attributes and add the corresponded Theia settings if they don't exist yet.

[azatsarynnyy]

Also, that Theia extension should take into account that not all of the Che Workspace attributes are the settings for Theia.
The extension should be able to distinguish it. Such attributes can be prefixed with preference, e.g.:

"attributes": {
  "plugin.org.eclipse.che.vscode-redhat.java.preference.java.jdt.ls.vmargs": "-noverify -Xmx1G -XX:+UseG1GC -XX:+UseStringDeduplication",
  "plugin.org.eclipse.che.vscode-redhat.java.preference.java.home": "/home/user/jdk11"
...
}

[tsmaeder]

Can we please get rid of that syntax that matches part of the plugin id and have some section per plugin? This current way is super confusing and error-prone.

[benoitf]

@tsmaeder : well I would say it's because workpace config is only allowing attributes in the current model.