vim-ccls: vim plugin for the ccls Language Server

This plugin supports some additional methods provided by ccls, which are not part of the standard Language Server Protocol (LSP). It does not implement a LSP client, but it relies on an existing LSP plugin, adding on top of it the ccls-specific features. Currently supported LSP clients are:

• ALE
• coc.nvim
• LanguageClient-neovim
• nvim-lspconfig
• vim-lsc
• vim-lsp

The plugin implements a tree viewer to display call, inheritance, and member hierarchies. Trees are built lazily, fetching children only when it is needed to expand a sub-tree, allowing to handle large trees.

The call hierarchy allows to visualise a tree of functions calling the function under the cursor (analogous to the Call Hierarchy View in Eclipse). Similarly, the callee tree visualises a hierarchy in the opposite direction, showing functions being called.

The base/derived hierarchy allows to visualise inheritance trees for the class under the cursor.

The member hierarchy allows to visualise a tree of members inside a type under the cursor.

Installation

This plugin can be installed with any vim plugin manager. One of the supported Language Server clients listed above needs to be installed and properly configured with ccls as language server in order for it to work.

If you have not done it already, build and install ccls, and configure your LSP client to use it (example instructions in the ccls wiki):

• ALE
• coc.nvim
• LanguageClient-neovim
• nvim-lspconfig
• vim-lsc
• vim-lsp

In order for ccls to work, make sure to correctly set up your project, by either providing a compilation database (compile_commands.json) or a .ccls configuration file.

Commands

The plugin provides the following commands. Hierarchy commands will open a tree-like buffer, while the other commands will populate the quickfix list.

• CclsBase: Get a list of base classes for the symbol under the cursor.
• CclsBaseHierarchy: Get a tree of inheritance ancestors for the symbol under cursor.
• CclsDerived: Get a list of derived classes for the symbol under the cursor.
• CclsDerivedHierarchy: Get a tree of inheritance descendants for the symbol under cursor.
• CclsCallers: Get a list of functions calling the function under the cursor.
• CclsCallHierarchy: Get a hierarchy of functions calling the function under the cursor.
• CclsCallees: Get a list of functions called by the function under the cursor.
• CclsCalleeHierahy: Get a hierarchy of functions called by the function under the cursor.
• CclsMembers/CclsMemberFunctions/CclsMemberTypes: Get a lists of members for the symbol under cursor.
• CclsMemberHierarchy/CclsMemberFunctionHierarchy/CclsMemberTypeHierarchy: Get a tree of members for the symbol under cursor.
• CclsVars: Get a list of document variables.

Hierarchy commands accept an optional parameter -float to open the hierarchy in a floating window instead of a split (Neovim only).

Settings

It is possible to automatically close a tree buffer when jumping to a location:

let g:ccls_close_on_jump = v:true

To control how many levels of depth in the sub-tree are fetched for each request, when building a tree (a large value may make execution slow when generating large trees):

let g:ccls_levels = 1

The size and position of the tree window can be set:

let g:ccls_size = 50
let g:ccls_position = 'botright'
let g:ccls_orientation = 'horizontal'

The size of the floating window (Neovim only) can be controlled:

let g:ccls_float_width = 50
let g:ccls_float_height = 20

The following <Plug> mappings are available to interact with a tree buffer:

<Plug>(yggdrasil-toggle-node)
<Plug>(yggdrasil-open-node)
<Plug>(yggdrasil-close-node)
<Plug>(yggdrasil-execute-node)

The default key bindings are:

nmap <silent> <buffer> o    <Plug>(yggdrasil-toggle-node)
nmap <silent> <buffer> <cr> <Plug>(yggdrasil-execute-node)
nnoremap <silent> <buffer> q :q<cr>

They can be disabled and replaced with custom mappings:

let g:yggdrasil_no_default_maps = 1
au FileType yggdrasil nmap <silent> <buffer> o <Plug>(yggdrasil-toggle-node)

Debugging

If you encounter any problem, the first step for troubleshooting is to enable logging, by setting the following variable:

let g:ccls_log_file = expand('~/my_log_file.txt')

License

This software is distributed under the MIT license. The full text of the license is available in the LICENSE file distributed alongside the source code.