spacemacs/layers/+tools/lsp/README.org

LSP layer

• Description
  • Features:
• Configuration
  • Derived layers
    • spacemacs/lsp-bind-keys-for-mode mode
  • Variables
  • Diagnostics
• Future additions/improvements
  • Make spacemacs/lsp-bind-keys-for-mode bind conditionally
• References

Description

This layer adds support for basic language server protocol packages speaking language server protocol.

Different language servers may support the language server protocol to varying degrees and they may also provide extensions; check the language server's website for details. M-x lsp-capabilities in a LSP buffer to list capabilities of the server.

Features:

• Cross references (definitions, references, document symbol, workspace symbol search and others)
• Workspace-wide symbol rename
• Symbol highlighting
• Flycheck
• Completion with company-lsp
• Signature help with eldoc
• Symbol documentation in a child frame (lsp-ui-doc)
• Navigation using imenu

Configuration

The LSP ecosystem is based on two packages: lsp-mode and lsp-ui. Please check out their documentation.

If you add lsp-*-enable to major mode hooks for auto initialization of language clients, customize lsp-project-whitelist lsp-project-blacklist to disable projects you don't want to enable LSP.

Derived layers

A number of elisp functions have been added to facilitate development of derived layers.

spacemacs/lsp-bind-keys-for-mode mode

Binds keys to a number of lsp features useful for all/most modes for the given major mode.

The prefix conventions suggested in spacemacs CONVENTIONS.org have been observed, where appropriate.

The default bindings are listed below. Derived language server layers should extend this list.

binding	function
m = b	format buffer (lsp)
m g i	goto implementation
m g t	goto type-definition
m g a	goto viewport symbol (avy)
m g m	browse file symbols (lsp-ui-imenu)
m g d	find definitions
m g r	find references
m g s	find-workspace-symbol
m g p	jump prev (lsp-ui-peek stack - see Note 1)
m g n	jump next (lsp-ui-peek stack - see Note 1)
m g f	jump to flycheck error
m h h	describe thing at point
m l r	lsp-restart-workspace
m l a	execute code action
m r r	rename
m T d	toggle documentation overlay
m T F	toggle documentation overlay function signature
m T s	toggle symbol info overlay
m T S	toggle symbol info overlay symbol name
m T I	toggle symbol info overlay duplicates

Note 1: There is a window local jump list dedicated to cross references

Variables

A number of configuration variables have been exposed via the LSP layer config.el. Sensible defaults have been provided, however they may all be overridden in your .spacemacs, or dynamically using the bindings added under the derived mode t prefix by (spacemacs/lsp-bind-keys-for-mode mode)

Variable name	Default	Description
lsp-ui-remap-xref-keybindings	nil	When non-nil, xref keybindings remapped to lsp-ui-peek-find-{definition,references}
lsp-ui-doc-enable	t	When non-nil, the documentation overlay is displayed
lsp-ui-doc-include-signature	nil	When nil, signature omitted from lsp-ui-doc overlay (this is usually redundant)
lsp-ui-sideline-enable	t	When non-nil, the symbol information overlay is displayed
lsp-ui-sideline-show-symbol	nil	When non-nil, the symbol information overlay includes symbol name (redundant for c-modes)
lsp-ui-peek-expand-by-default	nil	When non-nil, lsp-ui-peek expands file matches automatically (may degrade performance)

Diagnostics

If some features do not work as expected, here is a common check list.

• M-x lsp-capabilities If the LSP workspace is initialized correctly
• M-: xref-backend-functions should be (lsp--xref-backend) for cross references
• M-: completion-at-point-functions should be (lsp-completion-at-point) for completion

Future additions/improvements

Make spacemacs/lsp-bind-keys-for-mode bind conditionally

i.e. only bind keys if the language server supports the capability (queried using lsp-capabilities). lsp-capabilities uses current buffer to determine the language server, so this would probably entail adding the bindings dynamically in a mode hook.

References

• lsp-mode repo
• lsp-ui repo