`--matlabLaunchCommandArgs` does not accept value starting with "-" (Not enough arguments following)

[NOBUTOKA]

Describe the bug
When passing a value starting with - to --matlabLaunchCommandArgs, the server exits with a Not enough arguments following: matlabLaunchCommandArgs error, while other strings work as expected.

To Reproduce
From the repository root (after building out/index.js):

1. Run:

   node out/index.js --stdio --matlabLaunchCommandArgs "xxx"

   The server starts normally.

2. Then run:

   node out/index.js --stdio --matlabLaunchCommandArgs "-xxx"

   The process exits with the following error (or similar):

   Not enough arguments following: matlabLaunchCommandArgs
   

Expected behavior
--matlabLaunchCommandArgs should accept arbitrary strings as its value, including strings that start with - (e.g. "-xxx"), and pass them through to MATLAB in the same way as "xxx".

Useful Information

• MATLAB-language-server: current main (commit: 6c7e6b4)
• Node.js: v24.11.1

Additional context
This looks like the value is not being counted as an argument for matlabLaunchCommandArgs, but I am not sure whether this is intended behavior or a bug in how the CLI options are parsed.

If you need additional information or logs, I can provide them.

[NOBUTOKA]

For reference, I was able to work around this locally by post-processing the parsed argv and treating all positional args (after --) as additional MATLAB launch arguments, while still preserving any value explicitly passed to --matlabLaunchCommandArgs.

In getCliArgs I changed it like this:

export function getCliArgs (args?: string[]): CliArgs {
  const cliParser = makeParser()
  const argv = (args != null) ? cliParser.parseSync(args) : cliParser.parseSync()

  // Keep the existing option value as string | undefined
  const current = argv[Argument.MatlabLaunchCommandArguments] as string | undefined

  // Local workaround:
  // When called as:
  //   node out/index.js --stdio --matlabLaunchCommandArgs foo -- -bar
  // treat all positional args after `--` as additional MATLAB launch arguments.
  if (Array.isArray((argv as any)._)) {
    const extra = (argv as any)._ as unknown[]
    if (extra.length > 0) {
      const extraStr = extra.join(' ')
      const base = current ?? ''                // only for concatenation
      const combined = base ? `${base} ${extraStr}` : extraStr
      argv[Argument.MatlabLaunchCommandArguments] = combined
    }
  }

  return argv
}

With this change:

• node out/index.js --stdio --matlabLaunchCommandArgs "foo"
  → MATLAB receives foo as launch arguments.
• node out/index.js --stdio --matlabLaunchCommandArgs "foo" -- -bar
  → MATLAB receives foo -bar as launch arguments.
• node out/index.js --stdio --matlabLaunchCommandArgs -- -bar
  → MATLAB receives -bar as launch arguments.

This keeps the existing --matlabLaunchCommandArgs <string> behavior working as before, but also allows passing additional arguments (including ones starting with -) after -- without triggering the Not enough arguments following: matlabLaunchCommandArgs error.
This is just one possible approach, but if the intended design is that --matlabLaunchCommandArgs should accept arbitrary MATLAB arguments (even those starting with -), something along these lines might be an option.

[dklilley]

Hi @NOBUTOKA, thanks for reaching out about this!

Can you give some more info about what you are trying to achieve and what additional arguments you are trying to pass to MATLAB?

[NOBUTOKA]

I have MATLAB Campus-Wide License and it can be activated only through online sign in, so I have to add -licmode onlinelicensing.
Additionally, in some (poor-X) system I need -nodisplay switch, not only -nodesktop and -nosplash switches.

[dklilley]

Thanks for the extra information!

Are you using the MATLAB extension for VS Code? If so, a licensing workflow can be accessed by enabling the "MATLAB: Sign In" setting.

Regarding the error, I was able to reproduce this with the same command you used above:

node out/index.js --stdio --matlabLaunchCommandArgs "-xxx"

However, I did not see the error when using single quotes:

node out/index.js --stdio --matlabLaunchCommandArgs '-xxx'

Can you give this a try to see if it resolves the issue you are seeing?

[NOBUTOKA]

Thanks for reply and digging the problem!

I'm using eglot on emacs, so unfortunately I can't use setting option.

Rgarding the single quote solution, at least in my environment, it has two problems.

1. It does not work when executed from shell(I tried zsh, bash, and sh), still have "Not enough arguments" Error. But It WORKS when executed from eglot process(no error), I don't know why.
   This problem is not so important (after all, we want to run lsp from editor), but it maybe offer us some information about this issue.
2. Even when it works, checking the actual matlab process with ps ax | grep matlab and result is following:

5452 ?        S      0:00 /bin/sh /path/to/matlab/2023b/bin/matlab -log -memmgr release -noAppIcon -nosplash -r addpath(fullfile('/path/to/MATLAB-language-server/out', '..', 'matlab')); initmatlabls('/tmp/matlabls_5003/matlabls_conn.json') -nodesktop -sd /path/to/my/project '-licmode onlinelicensing -nodisplay'

note that the argument passed by matlabLaunchCommandArgs is surrounded by single quate, and this matlab process dies immidiately.

[dklilley]

After some additional investigation, here is what I am seeing:

The original error ("Not enough arguments") appears to be a limitation of the yargs parser. Despite being quoted, yargs tries to parse anything beginning with - as additional arguments. The primary workaround I have found is to use equals syntax. For example, --matlabLaunchCommandArgs='-xxx' instead of --matlabLaunchCommandArgs '-xxx'. Is this something you have control over within Eglot?

The extra quotes being added in also appears to be an oddity from yargs. It appears that this behavior stems from the use of requiresArg. If I swap out requiresArg: true for default: '' in CliUtils.ts, the additional quotes are no longer injected.

[NOBUTOKA]

Thanks for your investigation!

I confirmed --matlabLaunchCommandArgs='-xxx' works without error on both shell and eglot, and after swapping requiresArg: true for default: '', the additional quotes are disappear, and Matlab has started successfully.

[dklilley]

Glad to hear it!

I will keep this issue open for now, so that some improvements can be made in this area in a future update.