[che-dev] Language servers per project

[Thomas Mäder <tmader@xxxxxxxxxx>]

Hi folks,

while working with jdt.ls I've come across an issue that has been 
bugging me for quite some time: we start an instance of a language 
server per root project in Che. I've long felt that this is wrong, and 
with multi-root workspaces coming to LSP, it will be even more wrong. 
Things like jre, libraries in the local maven repo do NOT exist once per 
project. Also, if we can't have references between projects (which is 
the state now), why even HAVE multiple projects? Concretely, I get an 
opaque url for references in class files from jdt.ls, which I can't 
really map to a project, so my code fails when trying to map a class 
file url to a project.

I am currently working around that issue by using per project proxies 
for a single instance of jdt.ls in the background. I would like to 
reverse this burden and make it the default for language servers to be 
initialized once per workspace. If a language server cannot run in this 
configuration, it is up to that language server launcher to start the 
appropriate instances as needed.

I'd like to hear from interested parties on why the decision to use per 
project LS was taken and what concrete problems (which language servers) 
arose with single LS per workspace. Also, what's the general opinion on 
this issue?

thx for your feedback,

/Thomas