Double quoted strings are semantically different in vimscript, and you probably don't want them (they break regexes).

Use double quoted strings when you need an escape sequence (such as "\n") or if you know it doesn't matter and you need to embed single quotes.

The matching behavior depends upon the user's ignorecase and smartcase settings and on whether you compare them with the =~, =~#, or =~? family of operators. Use the =~# and =~? operator families explicitly when comparing strings unless you explicitly need to honor the user's case sensitivity settings.

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 \m\C.

You are welcome to use other magic levels (\v) and case sensitivities (\c) so long as they are intentional and explicit.

Avoid using :s[ubstitute] as it moves the cursor and prints error messages. Prefer functions (such as search()) better suited to scripts.

For many vim commands, functions exist that do the same thing with fewer side effects. See :help functions() for a list of built-in functions.

Always use normal! instead of normal. The latter depends upon the user's key mappings and could do anything.

Avoid :s[ubstitute], as its behavior depends upon a number of local settings.

The same applies to other commands not listed here.

Error text may be locale dependant.

Loud scripts are annoying. Message the user only when:

• A long-running process has kicked off.
• An error has occurred.

Vimscript has unsafe, unintuitive behavior when dealing with some types. For instance, 0 == 'foo' evaluates to true.

Use strict comparison operators where possible. When comparing against a string literal, use the is# operator. Otherwise, prefer maktaba#value#IsEqual or check type() explicitly.

Check variable types explicitly before using them. Use functions from maktaba#ensure, or check maktaba#value or type() and throw your own errors.

Use :unlet for variables that may change types, particularly those assigned inside loops.

Use python only when it provides critical functionality, for example when writing threaded code.

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.

maktaba removes boilerplate, including:

• Plugin creation
• Error handling
• Dependency checking

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 VAM documentation for details).

Autoloading allows functions to be loaded on demand, which makes startuptime faster and enforces function namespacing.

Script-local functions are welcome, but should also live in autoload/ and be called by autoloaded functions.

Non-library plugins should expose commands instead of functions. Command logic should be extracted into functions and autoloaded.

[!] allows developers to reload their functions without complaint.

[abort] forces the function to halt when it encounters an error.

General commands go in plugin/commands.vim. Filetype-specific commands go in ftplugin/.

Excluding [!] prevents your plugin from silently clobbering existing commands. Command conflicts should be resolved by the user.

Place all autocommands in augroups.

The augroup name should be unique. It should either be, or be prefixed with, the plugin name.

Clear the augroup with autocmd! before defining new autocommands in the augroup. This makes your plugin re-entrable.

All key mappings should be defined in plugin/mappings.vim.

Partial mappings (see :help using-<Plug>.) should be defined in plugin/plugs.vim.

Use :setlocal and &l: instead of :set and & unless you have explicit reason to do otherwise.

• Use two spaces for indents
• Do not use tabs
• Use spaces around operators

  This does not apply to arguments to commands.

  let s:variable = "concatenated " . "strings" command -range=% MyCommand
• Do not introduce trailing whitespace

  You need not go out of your way to remove it.

  Trailing whitespace is allowed in mappings which prep commands for user input, such as "noremap <leader>gf :grep -f ".

• Restrict lines to 80 columns wide
• Indent continued lines by four spaces
• Do not align arguments of commands command -bang MyCommand call myplugin#foo() command MyCommand2 call myplugin#bar() command -bang MyCommand call myplugin#foo() command MyCommand2 call myplugin#bar()