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Completion with sources

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Qiming zhao edited this page Mar 12, 2021 · 60 revisions

Highlights of coc.nvim's completion

  • Full LSP completion support, especially snippet and additionalTextEdit feature. You'll understand why it's awesome when you experience it with a coc extension like coc-tsserver.
  • Completion resolving on completion item change, it does async completion resolve on completion item change and the detail and documentation will be shown in a float window when possible.
  • Asynchronous and parallel completion request. Unless using vim sources, your vim will never be blocked.
  • Incomplete request and cancel request support, only incomplete completion requests will be triggered on filtering completion items and cancellation requests are sent to servers only when necessary.
  • Start completion without timer. The completion will start after you type the first letter of a word by default and is filtered with new input after the completion has finished. Other completion engines use a timer to trigger completion so you always have to wait after the typed character.
  • Realtime buffer keywords. Coc will generate buffer keywords on buffer change in the background (with debounce), while some completion engines use a cache which isn't always correct. Plus, Locality bonus feature from VSCode is enabled by default.
  • Filter completion items when possible. When you do a fuzzy filter with completion items, some completion engines will trigger a new completion, but coc.nvim will filter the items when possible which makes it much faster. Filtering completion items on backspace is also supported.

Trigger mode of completion

There are 3 different trigger modes:

  • always, the default mode, which triggers completion on a letter inserted or triggerCharacters (or trigger pattern match) defined by the current activated sources.
  • trigger, only trigger completion when you type triggerCharacters (or trigger pattern match) defined by the completion sources.
  • none, disable auto trigger completion, you will have to trigger the completion manually.

Lots of completion behavior can be changed by using the configuration file, check out :h coc-config-suggest for details.

Limitation of coc.nvim's completion

By default, coc.nvim use its own completeopt option during completion to provide the best auto completion experience.

There's no function of coc.nvim that can be used as omnifunc because it's not possible to support all LSP completion features when using omnifunc.

For features like textEdit and additionalTextEdits(mostly used by automatic import feature) of LSP to work, you have to confirm completion, which is <C-y> by default in vim. Read the next section for example key-mappings.

Use <cr> to confirm completion

You have to remap <cr> to make sure it confirms completion when popup menu is visible since default behavior of <CR> could be different regard to current completion state and completeopt option.

inoremap <expr> <cr> pumvisible() ? "\<C-y>" : "\<C-g>u\<CR>"

Note: \<C-g>u is used to break undo level.

To make <cr> select the first completion item and confirm the completion when no item has been selected:

inoremap <silent><expr> <cr> pumvisible() ? coc#_select_confirm() : "\<C-g>u\<CR>"

to make coc.nvim format your code on <cr>:

inoremap <silent><expr> <cr> pumvisible() ? coc#_select_confirm() : "\<C-g>u\<CR>\<c-r>=coc#on_enter()\<CR>"

Use complete_info() if you need confirm completion only when there's selected complete item:

if exists('*complete_info')
  inoremap <silent><expr> <cr> complete_info(['selected'])['selected'] != -1 ? "\<C-y>" : "\<C-g>u\<CR>"
endif

Use <Tab> or custom key for trigger completion

You can make use of coc#refresh() for trigger completion like this:

" use <tab> for trigger completion and navigate to the next complete item
function! s:check_back_space() abort
  let col = col('.') - 1
  return !col || getline('.')[col - 1]  =~ '\s'
endfunction

inoremap <silent><expr> <Tab>
      \ pumvisible() ? "\<C-n>" :
      \ <SID>check_back_space() ? "\<Tab>" :
      \ coc#refresh()

Note: the <tab> could be remapped by another plugin, use :verbose imap <tab> to check if it's mapped as expected.

" use <c-space>for trigger completion
inoremap <silent><expr> <c-space> coc#refresh()

Some terminals may send <NUL> when you press <c-space>, so you could instead:

" use <c-space>for trigger completion
inoremap <silent><expr> <NUL> coc#refresh()

Use <Tab> and <S-Tab> to navigate the completion list:

inoremap <expr> <Tab> pumvisible() ? "\<C-n>" : "\<Tab>"
inoremap <expr> <S-Tab> pumvisible() ? "\<C-p>" : "\<S-Tab>"

Completion sources

Use command :CocList sources to get current completion source list.

Bundled sources.

Name Shortcut Description
around [A] Words of the current buffer.
buffer [B] Words of other open buffers.
file [F] Filename completion, auto detected.

Configuring sources

You can configure completion sources by using coc-settings.json

  • "coc.source.{name}.enable": controls if the source is enabled.
  • "coc.source.{name}.shortcut": shortcut used in completion menu.
  • "coc.source.{name}.priority": priority of the source, lower priority sources will be sorted after high priority sources when they have same score.
  • "coc.source.{name}.disableSyntaxes": syntax names used to disable source from completion, eg: ["comment", "string"]
  • "coc.source.around.firstMatch": Filter complete items by first letter strict match, default true.
  • "coc.source.buffer.firstMatch": Filter complete items by first letter strict match, default true.
  • "coc.source.buffer.ignoreGitignore": Ignore git ignored files for buffer words, default true.
  • "coc.source.file.trimSameExts": Filename extensions to trim extension names on file completion, default [".ts", ".js"]
  • "coc.source.file.ignoreHidden": Ignore completion for hidden files, default true.
  • coc.source.file.ignorePatterns: Ignore patterns of matcher module, default [].

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