Custom snippets for Clojure LSP

Custom snippets are defined in the Clojure LSP EDN configuration using the :additional-snipets key. The snippet body uses the same tab stop and placeholder syntax as Yasnipets, although the body is contained within a string.

Built-in snippets can include Clojure code for generating the text of the snippet when expanded. Custom snippets do not currently support evaluation of code in the snippet.

Clojuse LSP Configuration locations

Project specific configuration resides in .lsp/config.edn

User level configuration is either $XDG_CONFIG_HOME/clojure-lsp/config.edn or $HOME/.lsp/config

Snippet definition

The :additional-snippets key is associated with a vector or hash-maps, [{}{},,,] with each hash-map defining a snippet using the keys:

:name - name of the snippet, typed into the editor for completion

:detail - a meaningful description of the snippet

:snippet - the definition of the snippet, with tab stops and current-form syntax

The :snippet can be any text, ideally with syntax that is correct for the particular language

Snippet Tab Stops

Include $ with a number, e.g. $1,$2,$3, to include tab stops in the snippet. Once the snippet code has been generated, TAB key jumps through the tab stops in sequence, allowing customisation of a generic snippet.

$0 marks the final position of the cursor, after which TAB has no more positions in the snippet to jump to.

Snippet current-form

When a Clojure LSP snipped includes $current-form then typing a snippet name in front of an existing Clojure form includes that form in the generated code.

{:additional-snippets [{:name "wrap-let-sexpr"
                        :detail "Wrap current sexpr in let"
                        :snippet "(let [$1 $current-form] $0)"}]}

Limited scope with current-form

A Snippet including $current-form is only active when typed in front of an existing expression. A snippet is not recognised when typed at the top level.

Placeholders

Tab Stops can also include default values or text used as hint on what each tab stop value is for. These are referred to as placeholders.

${1:default-value} is the form of a placeholder for tab stop 1. When the cursor tabs to tab stop 1, the default-value text is highlighted and replaces as soon as characters are typed.

Placeholder text is not replaced for $0 tab-stop, as the snippet interaction is effectively over at this point.

The deftest custom snippet shows examples of placeholders for three tab stops.

{:name "deftest"
 :detail "deftest clojure.test"
 :snippet
 "(deftest ${1:name}-test
    (testing \"${2:Context of the test assertions}\"
      (is (= ${3:assertion-values}))$4))
  $0"}

Escape string quotes in snippet body

Use \ character before the open and closing " character of any string that is part of the snippet body. For example, doc-strings in function definitions or the string in testing function.

Clojure code driven snippet - built-in snippets only

The built-in defn snippet uses Clojure code to help generate the snippet.

%s is a substitution point within a snippet, used by the standard Clojure format command, used to included either defn ^:private or defn-, depending on the value returned from the if expression.

:use-metadata-for-privacy? is a key from the Clojure LSP configuration

 {:label "defn-"
  :detail "Create private function"
  :insert-text (format "(defn%s ${1:name} [$2]\n  ${0:body})"
                       (if (:use-metadata-for-privacy? settings)
                         " ^:private"
                         "-"))}

The syntax for built-in snippets is slightly different that the :additional-syntax form. The internal form uses :label for :name and :insert-text for :snippet.

Hint

Clojure code only works for built-in snippets and not for :additional-snippets.

Clojure LSP is compiled by Graal to a native binary, including the built-in snippets. To include Clojure code in a snippet then consider submitting a pull request to the Clojure LSP project to add a built-in snippet.

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