Scala Metals fails

Scala Metals is a language server that communicates over JSON-RPC. It can be installed with

curl -Lo coursier https://git.io/coursier-cli && chmod +x coursier
./coursier bootstrap org.scalameta:metals_2.12:0.7.0 -o metals -f`

The contents of my servers.yml:

langservers:
  scala:
    - /Users/marduk/metals

I launched Jupyter Lab as follows:

node miniconda3/share/jupyter/lab/staging/node_modules/jsonrpc-ws-proxy/dist/server.js --port 3000 --languageServers servers.yml 

jupyter lab

I created a Scala notebook (using the Almond kernel) and in ~/Library/Caches/org.scalameta.metals/global.log I got the following error:

INFO  tracing is disabled for protocol LSP, to enable tracing of incoming and outgoing JSON messages create an empty file at /Users/marduk/Library/Caches/org.scalameta.metals/lsp.trace.json
INFO  Starting Metals server with configuration: MetalsServerConfig(
  bloop-protocol=BloopProtocol(auto),
  glob-syntax=GlobSyntaxConfig(uri),
  status-bar=StatusBarConfig(off),
  slow-task=SlowTaskConfig(off),
  execute-client-command=ExecuteClientCommandConfig(off),
  show-message=ShowMessageConfig(on),
  show-message-request=ShowMessageRequestConfig(on),
  no-initialized=false,
  compilers=PresentationCompilerConfigImpl(false,None,None,Map(scala/collection/mutable/ -> mutable., java/util/ -> ju.),Ascii,true,true,true,true,true,20,SECONDS),
  http=false,
  input-box=false,
  icons=none,
  statistics=StatisticsConfig(default)
)
INFO  logging to file /.metals/metals.log
Sep 01, 2019 9:45:07 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint fallbackResponseError
SEVERE: Internal error: java.nio.file.AccessDeniedException: /.metals

So it seems that Metals cannot create the directory .metals in the current workspace. I did some research and it appears that the workspace for the language server is set by jsonrpc-ws-proxy/dist/server.js.

Metals works in all the major editors, but it would be awesome to have it available in JupyterLab. See Integrating a new editor for details.

[sbrunk]

Since #92 has been merged, I just tried again using a dev build on master. I get a fully resolved path under $HOME now and Metals starts up fine! 🎉

Thanks for the fast fix! I guess this issue can be closed now.

[sbrunk]

Thank you all for the pointers! This is how rootUri looks in the init message:

[Trace - 08:11:28 AM] Received request 'initialize - (0)'
Params: {
  "processId": null,
  "rootUri": "file:///~/tmp/jupyterlab-lsp",
  ...

I tried starting jupyter lab from somewhere outside $HOME as suggested by @bollwyvl and it seems Metals is starting up normally. I can see it creating its startup files, there’s LSP communication in lsp.trace.json, and the status bar says "fully initialized.

We still don’t get back anything really usable as most answers are empty.

[Trace - 06:58:41 PM] Sending notification 'textDocument/publishDiagnostics'
Params: {
  "uri": "file:///private/tmp/jupyter-lsp/scala.ipynb",
  "diagnostics": []
}

But I assume that’s because Metals doesn’t support Scala script files yet and has nothing to do with jupyterlab-lsp.

So I guess fully resolving rootPath on the server (#91) should solve the issue here.