Allow for relative paths in java home config

[dlobsinger]

This change is an implementation to allow for the path provided in metals.javaHome to be a relative path from the root directory of the workspace.

The current behaviour when calling getJavaHome is that the path must be an absolute path or is resolved to a path relative to the system root /. If a user has a JDK located in their project directory, for example by using a nix profile to install a JDK in the same directory, it would be convenient to allow for the Metals configuration to use a path relative to the workspace.

[kpodsiad]

Thanks for your another contribution ;) I think we could simplify it a little bit, that immediate execution part wasn't obvious for me :c

[kpodsiad]

I was thinking about little bit more verbose

export function getJavaHomeFromConfig(): string | undefined {
  const javaHomePath = workspace
    .getConfiguration("metals")
    .get<string>("javaHome");
  if (javaHomePath?.trim() && !path.isAbsolute(javaHomePath)) {
    const pathSegments = [
      workspace.workspaceFolders?.[0]?.uri.fsPath,
      javaHomePath,
    ].filter((s): s is string => s != null);
    return path.resolve(...pathSegments);
  } else {
    return javaHomePath;
  }
}

It's not as concise as what you're proposing but I find it easier to read ;)

Also, extension.ts is an enormous file, moving this function to e.g. util.ts might be a good idea.

[dlobsinger]

Good point about moving this into util.ts - I wasn't sure whether it would be better to have as little impact in the scope of the code, or to have a more verbose implementation. I'll make those changes.

[kpodsiad]

LGTM!