Emacs Scala IDE using lsp-mode to connect to Metals.
An example to setup lsp-metals using use-package:
(use-package lsp-metals
:ensure t
:custom
;; You might set metals server options via -J arguments. This might not always work, for instance when
;; metals is installed using nix. In this case you can use JAVA_TOOL_OPTIONS environment variable.
(lsp-metals-server-args '(;; Metals claims to support range formatting by default but it supports range
;; formatting of multiline strings only. You might want to disable it so that
;; emacs can use indentation provided by scala-mode.
"-J-Dmetals.allow-multiline-string-formatting=off"
;; Enable unicode icons. But be warned that emacs might not render unicode
;; correctly in all cases.
"-J-Dmetals.icons=unicode"))
;; In case you want semantic highlighting. This also has to be enabled in lsp-mode using
;; `lsp-semantic-tokens-enable' variable. Also you might want to disable highlighting of modifiers
;; setting `lsp-semantic-tokens-apply-modifiers' to `nil' because metals sends `abstract' modifier
;; which is mapped to `keyword' face.
(lsp-metals-enable-semantic-highlighting t)
:hook (scala-mode . lsp))