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The syntax foldmethod is great, but sometimes I just want to fold the comments in a source file.
Also syntax folding of comments only works for C-Style comments like:
/*
...
*/
But not for comment boilerplate like:
//
//
// ...
//
Or even for comment blocks in non-C-like languages like:
#
#
# ...
#
How can I configure this with vim?
Folding only the comments is fairly easy by using foldmethod=expr:
set foldmethod=expr foldexpr=getline(v:lnum)=~'^\\s*'.&commentstring[0]
This will simply check if the line starts with any amount of whitespace followed by a comment character. Note that this is fairly naïve and may not work for all languages since commentstring can be more complex than just a single character. So you may want to use a autocmd to be more specific:
autocmd FileType c setlocal foldmethod=expr foldexpr=getline(v:lnum)=~'^\\s*//'
autocmd FileType python setlocal foldmethod=expr foldexpr=getline(v:lnum)=~'^\\s*#'
For more information about fold-expr, see:
Using syntax folding and comment folding is more involved; this would require modifing the syntax file in /usr/share/vim/vim74/syntax/*.vim, and will be specific to the language you're using.
Note that some filetypes already do this! For example from ruby.vim:
if !exists("ruby_no_comment_fold")
syn region rubyMultilineComment start="\%(\%(^\s*#.*\n\)\@<!\%(^\s*#.*\n\)\)\%(\(^\s*#.*\n\)\{1,}\)\@=" end="\%(^\s*#.*\n\)\@<=\%(^\s*#.*\n\)\%(^\s*#\)\@!" contains=rubyC
syn region rubyDocumentation start="^=begin\ze\%(\s.*\)\=$" end="^=end\%(\s.*\)\=$" contains=rubySpaceError,rubyTodo,@Spell fold
else
syn region rubyDocumentation start="^=begin\s*$" end="^=end\s*$" contains=rubySpaceError,rubyTodo,@Spell
endif
\s in one of the sets. Unsure if needed or not, but I suspect it might be.)
# is at the start of the line. Thanks for the edit!
May 8, 2020 at 0:48
:help option-backslash. I tend to prefer to define a function and set options that take an expression (and autocmds, etc.) to the function call, in order to avoid too many levels of escaping.
I like folding with indent but including the comments in the fold (I mean each comment get the same level of fold as the previous line).
Unfortunately, foldignore keyword just works for one line comments. So I fold with expr in vimrc:
set foldmethod=expr
set foldexpr=FoldMethod(v:lnum)
function! FoldMethod(lnum)
"get string of current line
let crLine=getline(a:lnum)
" check if empty line
if empty(crLine) "Empty line or end comment
return -1 " so same indent level as line before
endif
" check if comment
let a:data=join( map(synstack(a:lnum, 1), 'synIDattr(v:val, "name")') )
if a:data =~ ".*omment.*"
return '='
endif
"Otherwise return foldlevel equal to indent /shiftwidth (like if
"foldmethod=indent)
else "return indent base fold
return indent(a:lnum)/&shiftwidth
endfunction
The last block :
indent(a:lnum)/&shiftwidth
Returns a foldlevel base on indent.
And the other one :
join( map(synstack(a:lnum, 1), 'synIDattr(v:val, "name")') )
Checks if the first character of the line is consider as a comment with the syntax. So it is a good way to merge indent and syntax folding with expression, the most advanced folding.
Note that you can also "set foldtext" depending on how you want the result to look like.
You can visually select commented block with vac and then create a manual fold zf.
Comment text object may be language extension to set of standard vim text objects. Tested it with Go syntax.
ac is not a builtin. But with tpope’s commentary gc is a text object. So better solutions are zfac, zfgc, or zfip at worst