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Language agnostic vim plugin for folding and motion based on indentation.
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README.md

vim-anyfold

Generic folding mechanism and motion based on indentation. Fold anything that is structured into indented blocks. Quickly navigate between blocks.

Short Instructions

Using this plugin is easy: Activate vim-anyfold by the command :AnyFoldActivate and deal with folds using Vim's built-in fold commands. Use key combinations [[ and ]] to navigate to the beginning and end of the current open fold. Use ]k and [j to navigate to the end of the previous block and to the beginning of the next block. For more detailed documentation, read the included vim doc :h anyfold or continue reading.

Introduction

This Vim plugin comes with the following features:

  • Folding mechanism based on indented blocks that has a very intuitive and predictable behaviour (see examples below).
  • Results comparable to syntax aware folding methods but fast and generic algorithm that does not rely on language specific rules.
  • Works out of the box for any filetypes, optimal results for all indented languages (including properly indented curly brace languages).
  • Shortcuts to navigate to beginning / end of a block and to previous / next indented block.
  • Can handle corner cases with ease (comments, varying indentation widths, line breaks).
  • Fast update mechanism that keeps folds in sync with buffer.

It has the following shortcomings:

  • Can not correctly fold mismatched indentation and thus should only be used together with disciplined programming style (or in combination with Vim's equalprg autoindent feature).

Advantages over foldmethod=indent

  • foldmethod=indent only works for indents that are a multiple of shiftwidth and thus fails for aligned code lines and inconsistent indentation. Vim-anyfold correctly defines folds for arbitrary indents.
  • vim-anyfold recognizes braces as part of indented blocks and correctly folds them. Vim-anyfold thus produces good folds not only for indented languages but also for e.g. C++ or Java.
  • vim-anyfold optionally folds multiline comments.

Be aware that vim-anyfold is much slower than foldmethod=indent and can reduce Vim's responsiveness. This is noticeable only when editing large files.

Examples

Python

python

Fortran

fortran

C++

cpp

Java

Note: this example is outdated since better defaults have been implemented for curly braces. java

Examples were recorded using

autocmd Filetype * AnyFoldActivate
let g:anyfold_fold_comments=1
set foldlevel=0
colorscheme solarized
hi Folded term=NONE cterm=NONE

Setup and usage

  1. Install this plugin with a vim plugin manager.

  2. Add the following lines to your vimrc (if not already present).

    filetype plugin indent on " required
    syntax on                 " required
    
    autocmd Filetype * AnyFoldActivate               " activate for all filetypes
    " or
    autocmd Filetype <your-filetype> AnyFoldActivate " activate for a specific filetype
    
    set foldlevel=0  " close all folds
    " or
    set foldlevel=99 " Open all folds

If you prefer to not activate vim-anyfold automatically, you can always invoke this plugin manually inside vim by typing :AnyFoldActivate.

  1. Use Vim's fold commands zo, zO, zc, za, ... to fold / unfold folds (read :h fold-commands for more information). Use key combinations [[ and ]] to navigate to the beginning and end of the current open fold. Use ]k and [j to navigate to the end of the previous block and to the beginning of the next block.

Additional remarks

  1. Supported folding commands: anyfold uses foldmethod=expr to define folds. Thus all commands that work with expression folding are supported.

  2. Fold display: anyfold's minimalistic display of closed fold assumes that folds are highlighted by your color scheme. If that is not the case, consider installing a suitable color scheme or highlight folds yourself by a command similar to

    hi Folded term=underline
  3. Lines to ignore: By default, anyfold uses the foldignore option to identify lines to ignore (such as comment lines and preprocessor statements). Vim's default is foldignore = #. Lines starting with characters in foldignore will get their fold level from surrounding lines. If anyfold_fold_comments = 1 these lines get their own folds. For instance, in order to ignore C++ style comments starting with // and preprocessor statements starting with #, set

    autocmd Filetype cpp set foldignore=#/

    This approach is fast but does not work for e.g. C style multiline comments and Python doc strings. If you'd like anyfold to correctly ignore these lines, add

    let g:anyfold_identify_comments=2

    to your vimrc. Please note that this may considerably slow down your Vim performance (mostly when opening large files).

  4. Large Files: anyfold causes long load times on large files, significantly longer than plain indent folding. By adding the following to your vimrc (and replacing <filetype>), anyfold is not initialized for large files:

    " activate anyfold by default
    augroup anyfold
        autocmd!
        autocmd Filetype <filetype> AnyFoldActivate
    augroup END
    
    " disable anyfold for large files
    let g:LargeFile = 1000000 " file is large if size greater than 1MB
    autocmd BufReadPre,BufRead * let f=getfsize(expand("<afile>")) | if f > g:LargeFile || f == -2 | call LargeFile() | endif
    function LargeFile()
        augroup anyfold
            autocmd! " remove AnyFoldActivate
            autocmd Filetype <filetype> setlocal foldmethod=indent " fall back to indent folding
        augroup END
    endfunction
    
  5. Customization: For expert configuration, anyfold triggers an event anyfoldLoaded after initialisation. This enables user-defined startup steps such as

    autocmd User anyfoldLoaded normal zv

    which unfolds the line in which the cursor is located when opening a file.

  6. Documentation: For more detailed instructions and information, read the included vim doc :h anyfold.

Options

All options can be either set globally

let g:<option>=<value>

or filetype specific

autocmd Filetype <filetype> let g:<option>=<value>
Option Values Default value Description
anyfold_fold_display 0, 1 1 Minimalistic display of closed folds
anyfold_motion 0, 1 1 Map motion commands to [[, ]], [j, ]k
anyfold_identify_comments 0, 1, 2 1 Identify lines to ignore for better fold behavior. 1: use foldignore, 2: use foldignore and syntax (slow)
anyfold_fold_comments 0, 1 0 Fold multiline comments
anyfold_comments list of strings ['comment', 'string'] Names of syntax items that should be ignored. Only used if anyfold_identify_comments = 2.
anyfold_fold_toplevel 0, 1 0 Fold subsequent unindented lines
anyfold_fold_size_str string '%s lines' Format of fold size string in minimalistic display
anyfold_fold_level_str string ' + ' Format of fold level string in minimalistic display

Complementary plugins

Here is a small list of plugins that I find very useful in combination with vim-anyfold:

  • Cycle folds with one key, much more efficient than Vim's built-in folding commands: vim-fold-cycle
  • Indent based text objects are not (yet) implemented in vim-anyfold, but this plugin works fine (even though blocks are defined in a slightly different way): vim-indent-object

Acknowledgements

I thank the following people for their contribution

  • Greg Sexton for allowing me to use his function for improved fold display.
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