Built-in

Vim has built-in support for completions in insert or replace modes.See :help ins-completion.

By default, Vim uses separate Emacs style key bindings (<C-x C-key>)for different kinds of completions.

There are two plugins to use a single Tab key for completions:

• SuperTab
• VimCompletesMe

There is also AutoComplPop to automatically pop up completions.

VimCompletesMe

Why

Count source lines of code (VimScript comments start with "):

; cat supertab.vim | egrep -v '^("|([[:blank:]]*$))' | wc -l
923
; cat VimCompletesMe.vim | egrep -v '^("|([[:blank:]]*$))' | wc -l
82

Period.

Configuration

Without any configuration, the Tab key will, depending on the context, offer:

• Vim’s local keyword completion (Ctrl-X_Ctrl-N)
• File path completion when typing a path (Ctrl-X_Ctrl-F)
• Omni-completion after typing a period or an arrow operator (Ctrl-X_Ctrl-O)

With a b:vcm_tab_complete variable,you can set the Tab key to use the following type of completions:

• Dictionary words (Ctrl-X_Ctrl-K)
• User-defined completion (Ctrl-X_Ctrl-U)
• Tags (Ctrl-X_Ctrl-])
• Vim command line (Ctrl-X_Ctrl-V)
• Omni completion (Ctrl-X_Ctrl-O)

If any of above types of completions fails to return any results,hitting Tab again will switch back to Vim’s local keyword completion.

You can set the b:vcm_tab_complete variable interactively, or in ~/.vimrc:

autocmd FileType text,markdown let b:vcm_tab_complete = 'dict'

AutoComplPop

Use Enter to commit completion.Use arrow keys (Up|Down) to select completions.

It works well for certain file types,while distracting on other types such as text.

External engine

YouCompleteMe

YouCompleteMe is a fast, as-you-type, fuzzy-search code completion engine.It has several completion engines:

• an identifier based engine that works with every programming language,
• a Clang based engine that provides native semantic completion for C-family languages,
• a Jedi-based completion engine for Python 2 and 3,
• an OmniSharp-based completion engine for C#,
• a combination of Gocode and Godef semantic engines for Go,
• a TSServer-based completion engine for TypeScript,
• a Tern-based completion engine for JavaScript,
• a racer-based completion engine for Rust,
• and an omnifunc-based completer for many other languages

YCM also provides semantic IDE-like features in a number of languages:

• finding declarations, definitions, usages, etc. of identifiers,
• displaying type information for classes, variables, functions etc.,
• displaying documentation for methods, members, etc. in the preview window,
• fixing common coding errors, like missing semi-colons, typos, etc.,
• semantic renaming of variables across files (JavaScript only).

Tho downside is it consumes a lot of RAM.

neocomplete

neocomplete maintains a cache of keywords in the current buffer.It requires Vim 7.3.885+ with Lua enabled.It sometimes be slower than YCM, but requires much less RAM.

You can configure it to use Tab key to complete,and/or automatically pops up completion menu.

Conclusions

• If we need basic completions that works out of box: VimCompletesMe;
• If we need auto-pop basic completions: AutoComplPop and VimCompletesMe;
• IDE like features: YouCompleteMe;
• a balance between features and resources: neocomplete.