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vimscriptguide.xml
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vimscriptguide.xml
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<?xml version = '1.0'?>
<?xml-stylesheet type="text/xsl" href="styleguide.xsl"?>
<GUIDE title="Google Vimscript Style Guide">
<p class="revision">
Revision 1.1
</p>
<address>
Nate Soares<br/>
Joshua Hoak<br/>
David Barnett<br/>
</address>
<OVERVIEW>
<CATEGORY title="Background">
<p>
This is a casual version of the vimscript style guide, because
vimscript is a casual language. When submitting vim plugin code, you
must adhere to these rules. For clarifications, justifications, and
explanations about the finer points of vimscript, please refer to the
<a href="vimscriptfull.xml">heavy guide</a>.
</p>
</CATEGORY>
</OVERVIEW>
<CATEGORY title="Portability">
<p>
It's hard to get vimscript right. Many commands depend upon the user's
settings. By following these guidelines, you can hope to make your
scripts portable.
</p>
<STYLEPOINT title="Strings">
<SUMMARY>Prefer single quoted strings</SUMMARY>
<BODY>
<p>
Double quoted strings are semantically different in vimscript, and
you probably don't want them (they break regexes).
</p>
<p>
Use double quoted strings when you need an escape sequence (such as
<code>"\n"</code>) or if you know it doesn't matter and you need to
embed single quotes.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Matching Strings">
<SUMMARY>
Use the <code>=~#</code> or <code>=~?</code> operator families over the
<code>=~</code> family.
</SUMMARY>
<BODY>
<p>
The matching behavior depends upon the user's ignorecase and smartcase
settings and on whether you compare them with the <code>=~</code>,
<code>=~#</code>, or <code>=~?</code> family of operators. Use the
<code>=~#</code> and <code>=~?</code> operator families explicitly
when comparing strings unless you explicitly need to honor the user's
case sensitivity settings.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Regular Expressions">
<SUMMARY>Prefix all regexes with <code>\m\C</code>.</SUMMARY>
<BODY>
<p>
In addition to the case sensitivity settings, regex behavior depends
upon the user's nomagic setting. To make regexes act like nomagic and
noignorecase are set, prepend all regexes with <code>\m\C</code>.
</p>
<p>
You are welcome to use other magic levels (<code>\v</code>) and case
sensitivities (<code>\c</code>) so long as they are intentional and
explicit.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Dangerous commands">
<SUMMARY>Avoid commands with unintended side effects.</SUMMARY>
<BODY>
<p>
Avoid using <code>:s[ubstitute]</code> as it moves the cursor and
prints error messages. Prefer functions (such as
<code>search()</code>) better suited to scripts.
</p>
<p>
For many vim commands, functions exist that do the same thing with
fewer side effects. See <code>:help functions()</code> for a list of
built-in functions.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Fragile commands">
<SUMMARY>Avoid commands that rely on user settings.</SUMMARY>
<BODY>
<p>
Always use <code>normal!</code> instead of <code>normal</code>. The
latter depends upon the user's key mappings and could do anything.
</p>
<p>
Avoid <code>:s[ubstitute]</code>, as its behavior depends upon a
number of local settings.
</p>
<p>
The same applies to other commands not listed here.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Catching Exceptions">
<SUMMARY>Match error codes, not error text.</SUMMARY>
<BODY>
<p>Error text may be locale dependent.</p>
</BODY>
</STYLEPOINT>
</CATEGORY>
<CATEGORY title="General Guidelines">
<STYLEPOINT title="Messaging">
<SUMMARY>Message the user infrequently.</SUMMARY>
<BODY>
<p>
Loud scripts are annoying. Message the user only when:
<ul>
<li>A long-running process has kicked off.</li>
<li>An error has occurred.</li>
</ul>
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Type checking">
<SUMMARY>Use strict and explicit checks where possible.</SUMMARY>
<BODY>
<p>
Vimscript has unsafe, unintuitive behavior when dealing with some
types. For instance, <code>0 == 'foo'</code> evaluates to true.
</p>
<p>
Use strict comparison operators where possible. When comparing against
a string literal, use the <code>is#</code> operator. Otherwise, prefer
<code>maktaba#value#IsEqual</code> or check <code>type()</code>
explicitly.
</p>
<p>
Check variable types explicitly before using them. Use functions from
<code>maktaba#ensure</code>, or check <code>maktaba#value</code> or
<code>type()</code> and throw your own errors.
</p>
<p>
Use <code>:unlet</code> for variables that may change types,
particularly those assigned inside loops.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Python">
<SUMMARY>Use sparingly.</SUMMARY>
<BODY>
<p>
Use python only when it provides critical functionality, for example
when writing threaded code.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Other Languages">
<SUMMARY>Use vimscript instead.</SUMMARY>
<BODY>
<p>
Avoid using other scripting languages such as ruby and lua. We can
not guarantee that the end user's vim has been compiled with support
for non-vimscript languages.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Boilerplate">
<SUMMARY>
Use <a href="https://github.com/google/maktaba">maktaba</a>.
</SUMMARY>
<BODY>
<p>
maktaba removes boilerplate, including:
<ul>
<li>Plugin creation</li>
<li>Error handling</li>
<li>Dependency checking</li>
</ul>
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Plugin layout">
<SUMMARY>Organize functionality into modular plugins</SUMMARY>
<BODY>
<p>
Group your functionality as a plugin, unified in one directory (or
code repository) which shares your plugin's name (with a "vim-" prefix
or ".vim" suffix if desired). It should be split into plugin/,
autoload/, etc. subdirectories as necessary, and it should declare
metadata in the addon-info.json format (see the
<a href="https://github.com/MarcWeber/vim-addon-manager/blob/master/doc/vim-addon-manager-additional-documentation.txt">VAM documentation</a> for details).
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Functions">
<SUMMARY>
In the autoload/ directory, defined with <code>[!]</code> and
<code>[abort]</code>.
</SUMMARY>
<BODY>
<p>
Autoloading allows functions to be loaded on demand, which makes
startuptime faster and enforces function namespacing.
</p>
<p>
Script-local functions are welcome, but should also live in autoload/
and be called by autoloaded functions.
</p>
<p>
Non-library plugins should expose commands instead of functions.
Command logic should be extracted into functions and autoloaded.
</p>
<p>
<code>[!]</code> allows developers to reload their functions
without complaint.
</p>
<p>
<code>[abort]</code> forces the function to halt when it encounters
an error.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Commands">
<SUMMARY>
In the plugin/commands.vim or under the ftplugin/ directory, defined
without <code>[!]</code>.
</SUMMARY>
<BODY>
<p>
General commands go in <code>plugin/commands.vim</code>.
Filetype-specific commands go in <code>ftplugin/</code>.
</p>
<p>
Excluding <code>[!]</code> prevents your plugin from silently
clobbering existing commands. Command conflicts should be resolved by
the user.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Autocommands">
<SUMMARY>
Place them in plugin/autocmds.vim, within augroups.
</SUMMARY>
<BODY>
<p>
Place all autocommands in augroups.
</p>
<p>
The augroup name should be unique. It should either be, or be prefixed
with, the plugin name.
</p>
<p>
Clear the augroup with <code>autocmd!</code> before defining new
autocommands in the augroup. This makes your plugin re-entrable.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Mappings">
<SUMMARY>
Place them in <code>plugin/mappings.vim</code>, using
<code>maktaba#plugin#MapPrefix</code> to get a prefix.
</SUMMARY>
<BODY>
<p>
All key mappings should be defined in
<code>plugin/mappings.vim</code>.
</p>
<p>
Partial mappings (see :help using-<Plug>.) should be defined in
<code>plugin/plugs.vim</code>.
</p>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Settings">
<SUMMARY>Change settings locally</SUMMARY>
<BODY>
<p>
Use <code>:setlocal</code> and <code>&l:</code> instead of
<code>:set</code> and <code>&</code> unless you have explicit
reason to do otherwise.
</p>
</BODY>
</STYLEPOINT>
</CATEGORY>
<CATEGORY title="Style">
<p>
Follow google style conventions. When in doubt, treat vimscript style
like python style.
</p>
<STYLEPOINT title="Whitespace">
<SUMMARY>
Similar to python.
<br/>
<br/>
</SUMMARY>
<BODY>
<ul>
<li>Use two spaces for indents</li>
<li>Do not use tabs</li>
<li>Use spaces around operators
<p>This does not apply to arguments to commands.</p>
<CODE_SNIPPET>
let s:variable = "concatenated " . "strings"
command -range=% MyCommand
</CODE_SNIPPET>
</li>
<li>Do not introduce trailing whitespace
<p>You need not go out of your way to remove it.</p>
<p>
Trailing whitespace is allowed in mappings which prep commands
for user input, such as
"<code>noremap <leader>gf :grep -f </code>".
</p>
</li>
<li>Restrict lines to 80 columns wide</li>
<li>Indent continued lines by four spaces</li>
<li>Do not align arguments of commands
<BAD_CODE_SNIPPET>
command -bang MyCommand call myplugin#foo()
command MyCommand2 call myplugin#bar()
</BAD_CODE_SNIPPET>
<CODE_SNIPPET>
command -bang MyCommand call myplugin#foo()
command MyCommand2 call myplugin#bar()
</CODE_SNIPPET>
</li>
</ul>
</BODY>
</STYLEPOINT>
<STYLEPOINT title="Naming">
<SUMMARY>
<p>
In general, use
<code>plugin-names-like-this</code>,
<code>FunctionNamesLikeThis</code>,
<code>CommandNamesLikeThis</code>,
<code>augroup_names_like_this</code>,
<code>variable_names_like_this</code>.
</p>
<p>Always prefix variables with their scope.</p>
</SUMMARY>
<BODY>
<SUBSECTION title="plugin-names-like-this">
<p>Keep them short and sweet.</p>
</SUBSECTION>
<SUBSECTION title="FunctionNamesLikeThis">
<p>Prefix script-local functions with <code>s:</code></p>
<p>Autoloaded functions may not have a scope prefix.</p>
<p>
Do not create global functions. Use autoloaded functions
instead.
</p>
</SUBSECTION>
<SUBSECTION title="CommandNamesLikeThis">
<p>Prefer succinct command names over common command prefixes.</p>
</SUBSECTION>
<SUBSECTION title="variable_names_like_this">
<p>Augroup names count as variables for naming purposes.</p>
</SUBSECTION>
<SUBSECTION title="Prefix all variables with their scope.">
<ul>
<li>Global variables with <code>g:</code></li>
<li>Script-local variables with <code>s:</code></li>
<li>Function arguments with <code>a:</code></li>
<li>Function-local variables with <code>l:</code></li>
<li>Vim-predefined variables with <code>v:</code></li>
<li>Buffer-local variables with <code>b:</code></li>
</ul>
<p>
<code>g:</code>, <code>s:</code>, and <code>a:</code> must always
be used.
</p>
<p>
<code>b:</code> changes the variable semantics; use it when you
want buffer-local semantics.
</p>
<p>
<code>l:</code> and <code>v:</code> should be used for consistency,
future proofing, and to avoid subtle bugs. They are not strictly
required. Add them in new code but don’t go out of your way to add
them elsewhere.
</p>
</SUBSECTION>
</BODY>
</STYLEPOINT>
</CATEGORY>
<p align="right">
Revision 1.1
</p>
<address>
Nate Soares<br/>
Joshua Hoak<br/>
David Barnett<br/>
</address>
</GUIDE>