Error on unsupported

[ignamartinoli]

Hey, really nice plugin, I love using it.
The other day I tried to use it on a JSON file. I forgot it wasn't possible to comment JSON, but after I did I received this error message:

E5108: Error executing lua Vim(lua):E5108: Error executing lua .../site/pack/packer/opt/Comment.nvim/lua/Comment/utils.lua:156: [Comment] Invalid commentstring - "". Run :h 'commentstring' for help.
stack traceback:
        [C]: in function 'assert'
        .../site/pack/packer/opt/Comment.nvim/lua/Comment/utils.lua:156: in function 'parse_cstr'
        ...site/pack/packer/opt/Comment.nvim/lua/Comment/optfunc.lua:62: in function 'opfunc'
        ...im/site/pack/packer/opt/Comment.nvim/lua/Comment/api.lua:279: in function 'current'
        [string ":lua"]:1: in main chunk
        [C]: at 0x55d7ba838e46
stack traceback:
        [C]: at 0x55d7ba838e46

It's totally correct for the plugin to refuse to comment in a language that hasn't that feature.
But what I would suggest is avoiding to crash and break the user experience.
The plugin could show a yellow message under the statusline with something like

Comment.nvim: commenting unsupported

For example, in nvim-lspconfig, when a Language Server crashes, it's reported this way.

Thanks for your time and your awesome plugin

[numToStr]

Here's my take:

The plugin could show a yellow message under the statusline with something like

commenting unsupported doesn't provide any info on why the filetype is not supported. So I believe the current error message is very clear and helpful.

But what I would suggest is avoiding to crash and break the user experience.

It's "impossible" to get this error/crash unless you try something funny like comment json or text file, which i would call undefined behavior, in that case this panic make sense to me. And second reason for using assert here is to keep the code simple, rather than checking for commentstring at multiple places, i let it panic and abort the current function execution.

Comment.nvim/lua/Comment/utils.lua

Line 176 in 350bf0c

function U.parse_cstr(cfg, ctx)

this is the function, and it is used at 4 different places.

[ignamartinoli]

It's just a personal opinion,
but receiving the stack traceback, looks like when you query something weird on a website, and if it fails you receive internal info of the SQL tables structure like

DataTables warning: table id=grid2 - Requested unknown parameter '7' for row 16.