Neovim plugin

[qu1ncyk]

Resolves #988.

This PR adds a Neovim plugin that makes it easy to use the Rascal LSP in Neovim. To make the LSP work in Neovim, this PR includes fixes for a NullPointerException.

NullPointerException stack trace

java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.FileOperationsWorkspaceCapabilities.getDidCreate()" because the return value of "org.eclipse.lsp4j.WorkspaceClientCapabilities.getFileOperations()" is null
    at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315)
    at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320)
    at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1770)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.FileOperationsWorkspaceCapabilities.getDidCreate()" because the return value of "org.eclipse.lsp4j.WorkspaceClientCapabilities.getFileOperations()" is null
    at org.rascalmpl.vscode.lsp.rascal.RascalWorkspaceService.initialize(RascalWorkspaceService.java:61)
    at org.rascalmpl.vscode.lsp.BaseLanguageServer$ActualLanguageServer.lambda$initialize$4(BaseLanguageServer.java:260)
    at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768)
    ... 3 more

To be honest, I'm not sure what getDidCreate, getDidRename and getDidDelete do and whether it is necessary to invoke getFileOperations 3 times, but at least the error is gone.

This plugin only adds support for the Rascal LSP, not for the parametric LSP.

[jurgenvinju]

Interesting! Thanks for doing this. Is there an easy way to include terminal support? Like in a split screen?

[qu1ncyk]

I added a command :RascalTerminal, which opens the Rascal REPL in a new terminal window inside Neovim. By default, it uses the built-in :terminal, but this can be configured to use a third-party plugin that provides a more user-friendly terminal, such as toggleterm.nvim.

[DavyLandman]

Hi @qu1ncyk

Thanks for your work in this PR.

1. Could you review & sign our CLA
2. Can you open a separate PR with the bugfix? that way we can make sure that gets released with the next release
3. Can we have some kind of tests for the neovim plugin? so we know if something breaks?

[qu1ncyk]

Hi, thanks for reviewing. I signed the CLA and opened a PR with just the bugfix. I'll look into testing.

[qu1ncyk]

Hi, I added tests for the plugin.