Changing Vim indentation behavior by file type

You can add .vim files to be executed whenever vim switches to a particular filetype.

For example, I have a file ~/.vim/after/ftplugin/html.vim with this contents:

setlocal shiftwidth=2
setlocal tabstop=2

Which causes vim to use tabs with a width of 2 characters for indenting (the noexpandtab option is set globally elsewhere in my configuration).

This is described here: http://vimdoc.sourceforge.net/htmldoc/usr_05.html#05.4, scroll down to the section on filetype plugins.

Use ftplugins or autocommands to set options.

ftplugin

In ~/.vim/ftplugin/python.vim:

setlocal shiftwidth=2 softtabstop=2 expandtab

And don't forget to turn them on in ~/.vimrc:

filetype plugin indent on

(:h ftplugin for more information)

autocommand

In ~/.vimrc:

autocmd FileType python setlocal shiftwidth=2 softtabstop=2 expandtab

I would also suggest learning the difference between tabstop and softtabstop. A lot of people don't know about softtabstop.

edit your ~/.vimrc, and add different file types for different indents,e.g. I want html/rb indent for 2 spaces, and js/coffee files indent for 4 spaces:

" by default, the indent is 2 spaces. 
set shiftwidth=2
set softtabstop=2
set tabstop=2

" for html/rb files, 2 spaces
autocmd Filetype html setlocal ts=2 sw=2 expandtab
autocmd Filetype ruby setlocal ts=2 sw=2 expandtab

" for js/coffee/jade files, 4 spaces
autocmd Filetype javascript setlocal ts=4 sw=4 sts=0 expandtab
autocmd Filetype coffeescript setlocal ts=4 sw=4 sts=0 expandtab
autocmd Filetype jade setlocal ts=4 sw=4 sts=0 expandtab

refer to: Setting Vim whitespace preferences by filetype

Put autocmd commands based on the file suffix in your ~/.vimrc

autocmd BufRead,BufNewFile   *.c,*.h,*.java set noic cin noexpandtab
autocmd BufRead,BufNewFile   *.pl syntax on

The commands you're looking for are probably ts= and sw=

I usually work with expandtab set, but that's bad for makefiles. I recently added:

:autocmd FileType make set noexpandtab

to the end of my .vimrc file and it recognizes Makefile, makefile, and *.mk as makefiles and does not expand tabs. Presumably, you can extend this.

Personally, I use these settings in .vimrc:

autocmd FileType python set tabstop=8|set shiftwidth=2|set expandtab
autocmd FileType ruby set tabstop=8|set shiftwidth=2|set expandtab

This might be known by most of us, but anyway (I was puzzled my first time): Doing :set et (:set expandtabs) does not change the tabs already existing in the file, one has to do :retab. For example:

:set et
:retab

and the tabs in the file are replaced by enough spaces. To have tabs back simply do:

:set noet
:retab

For those using autocmd, it is a best practice to group those together. If a grouping is related to file-type detection, you might have something like this:

augroup filetype_c
    autocmd!
    :autocmd FileType c setlocal tabstop=2 shiftwidth=2 softtabstop=2 expandtab
    :autocmd FileType c nnoremap <buffer> <localleader>c I/*<space><esc><s-a><space>*/<esc>
augroup end

Groupings help keep the .vimrc organized especially once a filetype has multiple rules associated with it. In the above example, a comment shortcut specific to .c files is defined.

The initial call to autocmd! tells vim to delete any previously defined autocommands in said grouping. This will prevent duplicate definition if .vimrc is sourced again. See the :help augroup for more info.

Today, you could try editorconfig, there is also a vim plugin for it. With this, you are able not only change indentation size in vim, but in many other editors, keep consistent coding styles.

Below is a simple editorconfig, as you can see, the python files will have 4 spaces for indentation, and pug template files will only have 2.

# 4 space indentation for python files
[*.py]
indent_style = space
indent_size = 4

# 2 space indentation for pug templates
[*.pug]
indent_size = 2

While you can configure Vim's indentation just fine using the indent plugin or manually using the settings, I recommend using a python script called Vindect that automatically sets the relevant settings for you when you open a python file. Use this tip to make using Vindect even more effective. When I first started editing python files created by others with various indentation styles (tab vs space and number of spaces), it was incredibly frustrating. But Vindect along with this indent file

Also recommend:

pythonhelper

python_match

python_ifold

In Lua (for Neovim users) you can use RUNTIMEPATH/ftplugin/*yourfiletype*.lua with options like:

vim.opt_local.shiftwidth  = 2
vim.opt_local.tabstop     = 2

Just be sure to use string values in quotes. For example:

vim.opt_local.foldmethod  = 'marker'

I use a utility that I wrote in C called autotab. It analyzes the first few thousand lines of a file which you load and determines values for the Vim parameters shiftwidth, tabstop and expandtab.

This is compiled using, for instance, gcc -O autotab.c -o autotab. Instructions for integrating with Vim are in the comment header at the top.

Autotab is fairly clever, but can get confused from time to time, in particular by that have been inconsistently maintained using different indentation styles.

If a file evidently uses tabs, or a combination of tabs and spaces, for indentation, Autotab will figure out what tab size is being used by considering factors like alignment of internal elements across successive lines, such as comments.

It works for a variety of programming languages, and is forgiving for "out of band" elements which do not obey indentation increments, such as C preprocessing directives, C statement labels, not to mention the obvious blank lines.