Configure LSP and Cider

Practicalli recommends starting with a minimal LSP configuration to avoid duplication of features that are already present in Cider. LSP features can then be enabled when you find them valuable.

practicalli/spacemacs.d configuration for Spacemacs included a minimal configuration for Cider and Clojure-lsp.

The Spacemacs lsp layer has a default configuration for all languages

The LSP Mode website provides examples of LSP features and there is a long list of LSP settings

Add clojure-backend 'cider as a clojure layer variable in .spacemacs to run Cider without any LSP features.

Choose your own preferences

This configuration uses predominately CIDER features as its a more established tool for Clojure development.

LSP UI elements and features are added to complement but not over-ride features in CIDER. See the LSP variables reference for other features that can be enabled.

Pre-requisites

SPC SPC allt-the-icons-install-fonts command will install icons that support the breadcrumb on headerline feature of LSP UI. This provides the director path, file name and symbol as a breadcrumb trail at the top of each buffer.

If this feature of LSP is not used, then the fonts do not need to be installed.

Optional - clj-kondo

The clojure-lsp project includes the latest clj-kondo binary, so any external install of the clj-kondo binary is optional.

Remove the flycheck-clj-kondo configuration, clojure-enable-linters 'clj-kondo, from the Spacemacs Clojure layer to avoid duplication of results, if a separate clj-kondo binary is on the execution path.

Spacemacs Clojure layer configuration

practicalli/spacemacs.d configuration uses clojure-mode features for indenting and aligning forms as you type.

In .spacemacs, the clojure layer variables allow for evaluating top-level forms from within a rich comment block. The size limit helps avoid slow-down of Emacs from too much output in the REPL buffer.

     (clojure :variables
     ;; clojure-backend 'cider               ;; use cider and disable lsp
     ;; clojure-enable-linters 'clj-kondo    ;; clj-kondo included in lsp
     cider-repl-display-help-banner nil      ;; disable help banner
     cider-pprint-fn 'fipp                   ;; fast pretty printing
     clojure-indent-style 'align-arguments
     clojure-align-forms-automatically t
     clojure-toplevel-inside-comment-form t  ;; evaluate expressions in comment as top level
     cider-result-overlay-position 'at-point ;; results shown right after expression
     cider-overlays-use-font-lock t
     cider-repl-buffer-size-limit 100        ;; limit lines shown in REPL buffer
     )

Spacemacs Clojure automatic indentation

Cider configuration in dotspacemacs/user-config section of .spacemacs configures the automatic alignment and indenting of Clojure code, following the Clojure style guide.

  ;; Indentation of function forms
  ;; https://github.com/clojure-emacs/clojure-mode#indentation-of-function-forms
  (setq clojure-indent-style 'align-arguments)
  ;;
  ;; Vertically align s-expressions
  ;; https://github.com/clojure-emacs/clojure-mode#vertical-alignment
  (setq clojure-align-forms-automatically t)
  ;;
  ;; Auto-indent code automatically
  ;; https://emacsredux.com/blog/2016/02/07/auto-indent-your-code-with-aggressive-indent-mode/
  (add-hook 'clojure-mode-hook #'aggressive-indent-mode)

Explore the LSP indentation

LSP can also carry out indentation. Remove the aggressive-indent-mode and the clojure-mode indentation and alignment to avoid clashes with the LSP formatting and indentation.

LSP layer variables

Add the lsp layer to .spacemacs and include the following variables for an uncluttered LSP UI.

The lsp variables reference covers more options available.

     (lsp :variables
          lsp-enable-on-type-formatting nil
          lsp-enable-indentation nil
          lsp-enable-symbol-highlighting t
          lsp-modeline--enable-diagnostics t
          lsp-ui-doc-show-with-cursor nil   ;; disable doc popup for cursor
          lsp-ui-doc-delay 2
          lsp-ui-sideline-enable nil
          lsp-lens-enable t
          treemacs-space-between-root-nodes nil
          lsp-file-watch-threshold 10000)

Customising symbol highlighting

Symbol highlighting can be toggled using the command lsp-toggle-symbol-highlighting and the startup state can be set using the lsp layer configuration variable lsp-enable-symbol-highlighting

The face used for highlighting will vary by theme. Use the Emacs customize command to configure the lsp-syntax-highliging-read face or add the theming layer to .spacemacs and add a custom face to docspacemacs/user-init section of .spacemacs

In this example, the default orange background color is removed and the font weigh set to bold.

(setq-default
    theming-modifications
      '((doom-gruvbox-light
         (lsp-face-highlight-read :background nil :weight bold))))

doom gruvbox light - bold highlight for lsp

Key bindings over-ridden by lsp include

, h h calls cider-doc without LSP enabled. With LSP enabled then describe-thing-at-point command is called instead. This is similar to cider-doc, however, it does not allow the navigation to the source code definition of the function.

Yas-snippets and LSP

LSP uses company-lsp mode and manages the auto-completion popup. Yasnippets do not seem to work with company-lsp (although it should be possible in theory).

SPC i s will run helm-yas and provides a menu to select and insert snippets into the current buffer. M-/ will expand a matching snippet too (although it seems to take a few tries).

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