chapters/42.markdown @ 8d3cdc4c9c2a

Plugin Layout in the Dark Ages
==============================

The first thing we need to talk about is how to structure our plugin.  In the
past this was a messy affair, but now there's a tool that makes the process of
installing Vim plugins much, *much* saner.

We need to go over the basic layout first, then we'll talk about how to restore
our sanity.

Basic Layout
------------

Vanilla Vim supports splitting plugins into multiple files.  There are a number
of different directories you can create under `~/.vim` that mean various things.

We'll cover the most important directories now, but don't stress out too much
about them.  We'll go over them one at a time as we create our Potion plugin.

Before we continue we need to talk about some vocabulary.

I've been using the word "plugin" to mean "a big ol' hunk of Vimscript that does
a bunch of related stuff".  Vim has a more specific meaning of "plugin", which
is "a file in `~/.vim/plugin/`".

Most of the time I'll be using the first definition.  I'll try to be clear when
I mean the second.

~/.vim/colors/
--------------

Files inside `~/.vim/colors/` are treated as color schemes.  For example: if you
run `:color mycolors` Vim will look for a file at `~/.vim/colors/mycolors.vim`
and run it.  That file should contain all the Vimscript commands necessary to
generate your color scheme.

We're not going to cover color schemes in this book.  If you want to create your
own you should copy an existing scheme and modify it.  Remember that `:help` is
your friend.

~/.vim/plugin/
--------------

Files inside `~/.vim/plugin/` will each be run once *every time* Vim starts.
These files are meant to contain code that you always want loaded whenever you
start Vim.

~/.vim/ftdetect/
----------------

Any files in `~/.vim/ftdetect/` will *also* be run every time you start Vim.

`ftdetect` stands for "filetype detection".  The files in this directory should
set up autocommands that detect and set the `filetype` of files, and *nothing
else*.  This means they should never be more than one or two lines long.

~/.vim/ftplugin/
----------------

Files in `~/.vim/ftplugin/` are different.

The naming of these files matters!  When Vim sets a buffer's `filetype` to
a value it then looks for a file in `~/.vim/ftplugin/` that matches.  For
example: if you run `set filetype=derp` Vim will look for
`~/.vim/ftplugin/derp.vim`.  If that file exists, it will run it.

Vim also supports directories inside `~/.vim/ftplugin/`.  To continue our
example: `set filetype=derp` will also make Vim run any and all `*.vim` files
inside `~/.vim/ftplugin/derp/`.  This lets you split up your plugin's `ftplugin`
files into logical groups.

Because these files are run every time a buffer's `filetype` is set they *must*
only set buffer-local options!  If they set options globally they would
overwrite them for all open buffers!

~/.vim/indent/
--------------

Files in `~/.vim/indent/` are a lot like `ftplugin` files.  They get loaded
based on their names.

`indent` files should set options related to indentation for their filetypes,
and those options should be buffer-local.

Yes, you could simply put this code in the `ftplugin` files, but it's better to
separate it out so other Vim users will understand what you're doing.  It's just
a convention, but please be a considerate plugin author and follow it.

~/.vim/compiler/
----------------

Files in `~/.vim/compiler/` work exactly like `indent` files.  They should set
compiler-related options in the current buffer based on their names.

Don't worry about what "compiler-related options" means right now.  We'll cover
that later.

~/.vim/after/
-------------

The `~/.vim/after/` directory is a bit of a hack.  Files in this directory will
be loaded every time Vim starts, but *after* the files in `~/.vim/plugin/`.

This allows you to override Vim's internal files.  In practice you'll rarely
need this, so don't worry about it until you find yourself thinking "Vim itself
sets option `x`, but I want something different".

~/.vim/autoload/
----------------

The `~/.vim/autoload/` directory is an incredibly important hack.  It sounds
a lot more complicated than it actually is.

In a nutshell: `autoload` is a way to delay the loading of your plugin's code
until it's actually needed.  We'll cover this in more detail later when we
refactor our plugin's code to take advantage of it.

~/.vim/doc/
-----------

Finally, the `~/.vim/doc/` directory is where you can add documentation for your
plugin.  Vim has a huge focus on documentation (as evidenced by all the `:help`
commands we've been running) so it's important to document your plugins.

Exercises
---------

Reread this chapter.  I'm not kidding.  Make sure you understand (in a very
rough way) what each directory we've talked about does.

For extra credit, find some Vim plugins you use and look at how they structure
their files.