write a key command for a markdown comment

Question

I've been messing about with file type specific commands this evening (which is going to be very useful) and I'm trying to write a markdown comment command at the moment. I'm not sure how to go about this though.

So If I have the following text :

This is a bit 
of text that 
I'm going 
to comment 

I can run

visual line
highlight text to comment
shift i to insert at beginning
enter "[//]: # (

That does the start, and I think that all of this could be put to a key command. But then I'm left with the end.

This is how it should look :

[//]: # (This is a bit 
of text that 
I'm going 
to comment)

Happy to correct any wonky terminology, thanks!

edit - possible 'tag' suggestion of ftplugin :)

Answer 1

Vim creates marks for the beginning and the end of the last visual selection in the current buffer. You can use '< to move to the beginning and '> to move to end. In this way you can conveniently add any text you want before and after the visual selection. For example, I have a map for inserting a LaTeX underline command that spans the current visual selection, like so

vnoremap <buffer> <localleader>mu <ESC>`>a}<ESC>`<i\uline{<ESC>

1. <ESC>: leave visual mode
2. `>: go to end of last visual selection
3. a}: insert closing curly bracket after
4. <ESC>: leave insert mode
5. `<: go to beginning of last visual selection
6. i\uline{: insert the characters \uline that make up the underline command and the opening curly bracket
7. <ESC>: leave insert mode

I can use this as viwee,mu to visually select current word and the two following and 'surround' them with the underline command (, is my local leader). This turns "Ja|g ska bara", sa Alfons Åberg. into "\uline{|Jag ska bara}", sa Alfons Åberg.

You should be able to adapt this for your situation. Perhaps try something like

<ESC>`>a)<ESC>`<i[//]: # (<ESC>

Answer 2

Adding/removing/toggling comments is a common request. As such there are a few approaches

Commenting Plugins

Using a plugin like commentary (which I use), Nerd Commenter, EnhCommentify, tComment, ..., etc make managing comments for all sorts of filetypes much easier as well has giving a consistent interface.

For example commentary use gcc to toggle an entire line or use gc followed by a motion to toggle out an entire motion. e.g. gcip to toggle a paragraph.

Surround.vim

Using Tim Pope's surround.vim plugin can make surrounding with quotes, parens, braces, and tags pairs very simple. It can also be customized so you can add your own "surroundings".

Add the following to ~/.vim/after/ftplugin/markdown.vim:

let b:surround_{char2nr('#')} = "[//]: # (\r)"

Now you can select your text via v and then surround via S#.

For more help with surround see:

:h surround
:h surround-customizing

Change and paste

Example assuming you have text selected via v:

c[//]: # (<c-r>")<esc>

This works because c by default will "cut" the text to the default/unnamed register. Using <c-r> we can recall a register while in insert mode. The register in the example above is " aka unnamed register.

If you do this often enough it might be worth creating a mapping:

xnoremap gc c[//]: # (<c-r>")<esc>

Thoughts

Personally I would install a commenting plugin because it can be such a common operation and creating new mappings for all the filetypes you come across can get annoying quickly.

I would also recommend looking into surround.vim which feels like a very natural extension of Vim. Install repeat.vim to bring back the glory of . when using certain plugins.