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LSP layer

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1 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.

1.1 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
  • Consistent core key bindings in LSP modes

2 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.

2.1 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-navigation `both’ `simple’ or `peek’ to bind only xref OR lsp-ui-peek navigation functions
lsp-ui-remap-xref-keybindings nil When non-nil, xref key bindings 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)

The lsp-navigation variable defined in config.el allows you to define a preference for lightweight or pretty (using lsp-ui-peek) source navigation styles. By default, the lightweight functions are bound under SPC m g and the lsp-ui-peek variants under SPC m G. Setting lsp-navigation to either 'simple or 'peek eliminates the bindings under SPC m G and creates bindings under SPC m g according to the specified preference.

3 Key bindings

A number of lsp features useful for all/most modes have been bound to the lsp minor mode, meaning they’ll be available in all language layers based on the lsp layer.

3.1 Key binding prefixes

The key bindings are grouped under the following prefixes:

prefix name functional area
SPC m = format Source formatting
SPC m g goto Source navigation
SPC m G peek Source navigation (lsp-ui-peek overlay)
SPC m h help Help
SPC m b lsp/backend Catchall. Restart LSP backend, other implementation-specific functionality
SPC m r refactor What it says on the tin
SPC m T toggle Toggle LSP backend features (documentation / symbol info overlays etc.)

Some navigation key bindings (i.e. SPC m g / SPC m G) use an additional level of grouping:

prefix name functional area
SPC m <g/G> h hierarchy Heirarchy (i.e. call/inheritance hierarchy etc. )
SPC m <g/G> m member hierarchy Class/namespace members (functions, nested classes, vars

3.2 Core key bindings

The lsp minor mode bindings are:

binding function
SPC m = b format buffer (lsp)
SPC m g t goto type-definition (lsp)
SPC m g k goto viewport word (avy) (See Note 1)
SPC m g K goto viewport symbol (avy) (See Note 1)
SPC m g e browse flycheck errors
SPC m g M browse file symbols (lsp-ui-imenu)
Note Replaced by the lsp-ui-peek equivalents when lsp-navigation = ='peek
SPC m g i find implementations (lsp)
SPC m g d find definitions (xref/lsp)
SPC m g r find references (xref/lsp)
SPC m g s find-workspace-symbol (lsp-ui)
SPC m g p goto previous (xref-pop-marker-stack)
Note Omitted when lsp-navigation = ='peek or 'simple
  Bound under SPC m g rather than SPC m G when lsp-navigation = ='peek
SPC m G i find implementation (lsp-ui-peek)
SPC m G d find definitions (lsp-ui-peek)
SPC m G r find references (lsp-ui-peek)
SPC m G s find-workspace-symbol (lsp-ui-peek)
SPC m G p goto previous (lsp-ui-peek stack - see Note 2)
SPC m G n goto next (lsp-ui-peek stack - see Note 2)
SPC m h h describe thing at point
SPC m b r lsp-restart-workspace
SPC m b a execute code action
SPC m b c lsp-capabilities
SPC m r r rename
SPC m T d toggle documentation overlay
SPC m T F toggle documentation overlay function signature
SPC m T s toggle symbol info overlay
SPC m T S toggle symbol info overlay symbol name
SPC m T I toggle symbol info overlay duplicates

Note 1: Your language server may not distinguish between the word and symbol variants of this binding. Note 2: There is a window local jump list dedicated to cross references.

3.3 Language-specific key binding extensions

Some LSP server implementations provide extensions to the protocol, which can be leveraged using lsp-find-custom or lsp-ui-peek-find-custom. A number of additional functions have been provided to facilitate wrapping these extensions in a manner consistent with the lsp-navigation setting.

3.3.1 spacemacs/lsp-define-extensions layer-name kind request &optional extra-parameters

Use this to define an extension to the lsp find functions. An example from the c-c++ layer:

(spacemacs/lsp-define-extensions "c-c++" 'refs-address
                                 '(plist-put (lsp--text-document-position-params) :context '(:role 128)))

This defines the following interactive functions:

  • c-c++/find-refs-address
  • c-c++/peek-refs-address

3.3.2 spacemacs/lsp-bind-extensions-for-mode

Use this to bind one or more extensions under SPC m g and/or SPC m G, as dictated by the value of lsp-navigation. Using another example from the c-c++ layer:

(spacemacs/lsp-bind-extensions-for-mode mode "c-c++"
                                        "&" 'refs-address
                                        "R" 'refs-read
                                        "W" 'refs-write
                                        "c" 'callers
                                        "C" 'callees
                                        "v" 'vars)

With lsp-navigation set to 'both (the default), this is equivalent to:

(spacemacs/set-leader-keys-for-major-mode mode
  "g&" 'c-c++/find-refs-address
  "gR" 'c-c++/find-refs-read
  "gW" 'c-c++/find-refs-write
  "gc" 'c-c++/find-callers
  "gC" 'c-c++/find-callees
  "gv" 'c-c++/find-vars
  "G&" 'c-c++/peek-refs-address
  "GR" 'c-c++/peek-refs-read
  "GW" 'c-c++/peek-refs-write
  "Gc" 'c-c++/peek-callers
  "GC" 'c-c++/peek-callees
  "Gv" 'c-c++/peek-vars)

whereas with lsp-navigation set to 'peek, this is equivalent to:

(spacemacs/set-leader-keys-for-major-mode mode
  "g&" 'c-c++/peek-refs-address
  "gR" 'c-c++/peek-refs-read
  "gW" 'c-c++/peek-refs-write
  "gc" 'c-c++/peek-callers
  "gC" 'c-c++/peek-callees
  "gv" 'c-c++/peek-vars)


4 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

5 References

Author: Travis CI User

Created: 2019-01-22 Tue 20:42