Generate Go types and signatures for the LSP protocol

Setup

1. Make sure node and tsc are installed. There are detailed instructions below.
2. Get the typescript code for the jsonrpc protocol with git clone git@github.com:microsoft vscode-languageserver-node.git
   1. If you want to reproduce the existing files you need to be on a branch with the same git hash, for instance, git checkout 635ab1f

Usage

To generate the protocol types (x/tools/internal/lsp/protocol/tsprotocol.go) tsc go.ts && node go.js [-d dir] [-o out.go]

and for simple checking

gofmt -w out.go && golint out.go && go build out.go

-d dir names the directory into which the vscode-languageserver-node repository was cloned. It defaults to $(HOME).

-o out.go says where the generated go code goes. It defaults to tsprotocol.go.

To generate the client and server boilerplate (tsclient.go and tsserver.go) tsc requests.ts && node requests.js [-d dir] && gofmt -w tsclient.go tsserver.go

-d dir is the same as above. The output files are written into the current directory.

Notes

1. go.ts and requests.ts use the Typescript compiler's API, which is introduced in their wiki.
2. Because the Typescript and Go type systems are incompatible, go.ts and request.ts are filled with heuristics and special cases. Therefore they are tied to a specific commit of vscode-languageserver-node. The hash code of the commit is included in the header of tsprotocol.go and stored in the variable gitHash in go.ts. It is checked (see git() in go.ts) on every execution of go.ts.
3. Generating the ts*.go files is only semi-automated. Please file an issue if the released version is too far behind.
4. For the impatient, first change gitHash by hand (git() shows how to find the hash).
   1. Then try to run go.ts and requests.ts. This will likely fail because the heuristics don't cover some new case. For instance, some simple type like string might have changed to a union type string | [number,number]. (Look at the UnionTypeNode code near line 588 of go.ts.) Another example is that some formal parameter generated by requests.ts will have anonymous structure type, which is essentially unusable. (See the code related to ourTypes.)
   2. Next step is to try to move the generated code to internal/lsp/protocol and try to build gopls and its tests. This will likely fail because types have changed. Generally the fixes are fairly easy. (The code for ourTypes was a case where changes had to be made to requests.ts.)
   3. Since there are not adequate integration tests, the next step is to run gopls. A common failure will be a nil dereference, because some previously simple default is now in an optional structure.

Detailed instructions for installing node and typescript

(The instructions are somewhat different for Linux and MacOS. They install some things locally, so $PATH needs to be changed.)

1. For Linux, it is possible to build node from scratch, but if there‘s a package manager, that’s simpler.
   1. To use the Ubuntu package manager
      1. sudo apt update (if you can't sudo these instructions are not helpful)
      2. sudo apt install nodejs (this may install /usr/bin/nodejs rather than /usr/bin/node. For me, /usr/bin/nodejs pointed to an actual executable /etc/alternatives/nodejs, which should be copied to /usr/bin/node)
      3. sudo apt intall npm
   2. To build from scratch
      1. Go to the node site, and download the one recommended for most users, and then you‘re on your own. (It’s got binaries in it. Untar the file somewhere and put its bin directory in your path, perhaps?)
2. The Mac is easier. Download the macOS installer from nodejs, click on it, and let it install.
3. (There's a good chance that soon you will be asked to upgrade your new npm. sudo npm install -g npm is the command.)
4. For either system, node and nvm should now be available. Running node -v and npm -v should produce version numbers.
5. npm install typescript
   1. This will likely give warning messages that indicate you've failed to set up a project. Ignore them.
   2. Your home directory will now have new directories .npm and node_modules (and a package_lock.json file)
   3. The typescript executable tsc will be in node_modules/.bin, so put that directory in your path.
   4. tsc -v should print “Version 3.7.2” (or later). If not you may (as I did) have an obsolete tsc earlier in your path.
6. npm install @types/node (Without this there will be many incomprehensible typescript error messages.)