`--doc` CLI argument does not work

How are you using the lua-language-server?

Command Line

Which OS are you using?

Windows WSL

What is the issue affecting?

Other

Expected Behaviour

Document generation, as documented here:

https://luals.github.io/wiki/usage/#--doc

Actual Behaviour

rhys@RhysDesktop:~/example-lua$ ~/lua-language-server/bin/lua-language-server --doc ~/example-lua/
root uri = file:///home/rhys/example-lua/
script/cli/doc/export.lua:304: attempt to concatenate a nil value (local 'outputDir')
stack traceback:
        script/cli/doc/export.lua:304: in field 'serializeAndExport'
        script/cli/doc/init.lua:235: in upvalue 'callback'
        script/lclient.lua:129: in function <script/lclient.lua:128>
stack traceback:
        script/lclient.lua:123: in function 'await.errorHandle'
        script/await.lua:35: in function 'await.checkResult'
        (...tail calls...)
        [C]: in function 'xpcall'
        script/timer.lua:52: in upvalue 'mWakeup'
        script/timer.lua:93: in upvalue 'onTick'
        script/timer.lua:236: in function 'timer.update'
        script/lclient.lua:139: in method 'start'
        script/cli/doc/init.lua:201: in function 'cli.doc.runCLI'
        script/cli/init.lua:22: in main chunk
        [C]: in function 'require'
        /home/rhys/lua-language-server/main.lua:78: in main chunk
        (bootstrap.lua):85: in main chunk
        [C]: in ?
script/lclient.lua:124: [19:48:24.474][error][#0:script/lclient.lua:123]: script/cli/doc/export.lua:304: attempt to concatenate a nil value (local 'outputDir')
stack traceback:
        script/cli/doc/export.lua:304: in field 'serializeAndExport'
        script/cli/doc/init.lua:235: in upvalue 'callback'
        script/lclient.lua:129: in function <script/lclient.lua:128>
stack traceback:
        script/lclient.lua:123: in function 'await.errorHandle'
        script/await.lua:35: in function 'await.checkResult'
        (...tail calls...)
        [C]: in function 'xpcall'
        script/timer.lua:52: in upvalue 'mWakeup'
        script/timer.lua:93: in upvalue 'onTick'
        script/timer.lua:236: in function 'timer.update'
        script/lclient.lua:139: in method 'start'
        script/cli/doc/init.lua:201: in function 'cli.doc.runCLI'
        script/cli/init.lua:22: in main chunk
        [C]: in function 'require'
        /home/rhys/lua-language-server/main.lua:78: in main chunk
        (bootstrap.lua):85: in main chunk
        [C]: in ?

stack traceback:
        [C]: in function 'error'
        script/lclient.lua:124: in function 'await.errorHandle'
        script/await.lua:35: in function 'await.checkResult'
        (...tail calls...)
        [C]: in function 'xpcall'
        script/timer.lua:52: in upvalue 'mWakeup'
        script/timer.lua:93: in upvalue 'onTick'
        script/timer.lua:236: in function 'timer.update'
        script/lclient.lua:139: in method 'start'
        script/cli/doc/init.lua:201: in function 'cli.doc.runCLI'
        script/cli/init.lua:22: in main chunk
        [C]: in function 'require'
        /home/rhys/lua-language-server/main.lua:78: in main chunk
        (bootstrap.lua):85: in main chunk
        [C]: in ?
/home/rhys/lua-language-server/bin/lua-language-server: script/lclient.lua:149: two hours later ...
====== C -> S ======
====== S -> C ======
====================
stack traceback:
        [C]: in function 'error'
        script/lclient.lua:149: in method 'start'
        script/cli/doc/init.lua:201: in function 'cli.doc.runCLI'
        script/cli/init.lua:22: in main chunk
        [C]: in function 'require'
        /home/rhys/lua-language-server/main.lua:78: in main chunk
        (bootstrap.lua):85: in main chunk
        [C]: in ?

Reproduction steps

1. Create a new folder
2. Add any documented lua file, I used this:

---@param x number
function foo(x) end

3. Run lua-language-server --doc <path-to-folder>

Additional Notes

I tried this on both Windows and WSL with the same result.

Log File

No response

Start with script/cli/doc/export.lua at the serializeAndExport failure on line 304, then trace how script/cli/doc/init.lua invokes it for --doc. Reproduce the command against a folder containing the documented Lua file. Done means the command completes without the nil outputDir error and generates the expected documentation.