Many months ago, I had VSCode working with Antlrvsix. Back then, rather than release what I had, I decided to put it off because I was concentrating my effort on getting the server capabilities expanded. But, the main problem why I didn’t release a VSCode extension was that I could not support “semantic highlighting” in my server in a standardized way because the API I was using did not support it. Since then, the server capabilities have been enhanced. But, more importantly, I changed the API to get semantic highlighting in Antlrvsix to work with VSCode. I have now released Antlrvsix for VSCode to the Microsoft Marketplace for VSCode.
To get semantic highlighting working with VSCode, I decided to write a drop-in replacement for Microsoft’s Microsoft.VisualStudio.LanguageServer.Protocol API. While Microsoft does make a release of the API every three months or so, there are many features missing that have been in the LSP spec for years. Semantic highlighting is a crucial new addition, but I have no confidence that Microsoft will ever implement it based on the changes I’ve seen over the last year. This drop-in replacement is the current version with additions for semantic highlighting.
On the grammar transforms, I have a script for the “Trash” command-line tool of Antlrvsix to optimize the Java9 grammar partially. The transforms for expressions aren’t yet there, but so far, the optimized grammar parser works several times faster.