Theia/Che LSP Feature Gap

[tsmaeder]

Stuff to do for languages team

JDT.LS specific features

• Usages View
• Reuse jdt.ls workspace Theia: Investigate Reuse jdt.ls Workspace #10325
• File Structure View Theia: file structure view #10326
  Che file structure is different from "document symbols" in that it shows a tree and inherited members.
• Implementers Search Theia: Search for Implementers #10324
• Libraries Theia: Implement jdt.ls "libraries" feature #8965
• Che/Java Theia Contribution Create Che Java Contribution #8940
• Show class files for Java Open Editor on Library Class Files in Theia #9972
• UI for simple projects
  • Show classpath in dialog for java projects Theia: Show class path dialog #10327
  • Implement add jar
  • implement add source folder
  • Mark/Unmark as source folder actions
  • implement "create simple project wizard" (if applicable)
• Testing IDE ("run unit tests")
• Launching jdt.ls without opening a file
  This is trivial if we control the Java front end contribution: activation is done when a promise is fullfilled that the front end language contribution controls.
• Rename Refactoring
  Che offers extended UI (in particular a wizard with options and preview and structural changes) for renaming things. We have a custom command in che-ls-jdt that implements the back end for this. One thing that we will need to port is a way to apply those structural changes to the theia workspace.
• Move Refactoring
  A custom command will be implemented analogous to rename. UI will need to be written.
• Addressing a particular LS (aka jdt.ls) to use specific protocol extensions. Investigate Way to Address jdt.ls #8941
• Suport jdt.ls Status Reports Support jdt.ls Status Reports #9970. Let's us see when jdt.ls is ready.
• Support jdt.ls Progress Reports Theia: Show Progress Reports from jdt.ls #9971

Langugage servers

Might need to work on language servers or implement launcher plugins for them.

• Go integrated throught WIP: Add Golang Support in Che #9803
• Typescript Theia includes a TS language server
• Python
• C++ via https://github.com/eclipse/che/pull/7516/files

Architectural diffs lsp related

• Theia IDE talks directly to language servers running on the back end (via a JSONRPC proxy endpoint running in the back end). The back end language contribution is responsible for starting the language server and setting up a forwarding connection for the front end. As a consequence, Theia runs a new copy of a language server for each instance of the Theia front end running (open Theia in a second tab, for example). Currently, this means that a new eclipse workspace is allocated each time Theia starts jdt.ls, which is not acceptable for Che-in-Che (10 min startup time).
• Registration similar to VSCode
  Registration of languages and language servers is in the front end and based on Monaco languages and VSCode document selectors. When a language contribution is activated, a connection to the back end is activated that establishes a connection to an instance of the langugage server.