Mistook todo checkbox as a markdown link

[VimWei]

Environment

I use the built-in markdown plugin with gvim 9.1, without installing any third-party markdown filetype plugins.

• gvim_9.1.0309_x64_signed.exe
• Win 10 pro 22H2

Issue reproduction

1. :new
2. :set filetype=markdown
3. Add a space (just one space) and a markdown link after a todo checkbox:

* [x] [test](https://www.example.com)

We can see vim mistook todo checkbox [x] as a markdown link, and the x will be underlined.

• More clear: If I configure augroup MarkdownLinkConceal, the todo checkbox will be concealed as if it were a markdown link. However, the [ ] symbols around test are not concealed.

augroup MarkdownLinkConceal
    autocmd!
    autocmd FileType markdown
        \ syn region markdownLink matchgroup=markdownLinkDelimiter
        \ start="(" end=")" contains=markdownUrl keepend contained conceal
    autocmd FileType markdown
        \ syn region markdownLinkText matchgroup=markdownLinkTextDelimiter
        \ start="!\=\[\%(\_[^][]*\%(\[\_[^][]*\]\_[^][]*\)*]\%( \=[[(]\)\)\@="
        \ end="\]\%( \=[[(]\)\@=" nextgroup=markdownLink,markdownId skipwhite
        \ contains=@markdownInline,markdownLineStart concealends
augroup END

• Compare: If there are two or more spaces after todo checkbox, the issue disappear.

* [x] [test](https://www.example.com)

Reference

• similar issue: https://github.com/nextcloud/deck/issues/2640

[tpope]

I made a deliberate decision in https://github.com/tpope/vim-markdown/commit/6c1e41e4c4d95ccb024530d957c583ab807b5724 to allow a space in [link] (url). I've long since forgotten why, but it's a safe bet that it was in reaction to some parser. I guess I'll try tightening it up a bit.

[VimWei]

Thanks!