Continuing with my work in making Antlrvsix a Language Server Protocol server implementation, I created an extension for Visual Studio 2019 that uses the client API Microsoft.VisualStudio.LanguageServer.Client with the Eclipse Java Language Server Protocol implementation. This extension follows the steps outlined in an old article on creating LSP clients in Visual Studio. The extension source code is here. The code has been updated so that the only requirement is that you have the Java runtime downloaded and installed, and JAVA_HOME set to the top-level directory of the Java runtime. The code will prompt you for the path and warn you that it isn’t set properly.
Even as noted in the old MS documentation page, many of the client features are enabled, e.g., go to def, find all refs, reformat, hover, and typing completions. What is missing is building and debugging. But it is very usable.