feat(emacs): add Java support

Author: gekoke

modules/nixos/programs/emacs/default.nix

@@ -62,16 +62,25 @@ in
         # Python
         nodePackages.pyright
         ruff-lsp
+        # Java
+        jdk21
+        jdt-language-server
       ];
 
       elementary.home = {
         programs.emacs = {
           enable = true;
           package = emacsPackage;
+          extraConfig = ''
+            (setq lsp-java-server-install-dir "${pkgs.jdt-language-server}/share/java/jdtls")
+            (setq lsp-java-server-config-dir (concat (file-name-as-directory (xdg-config-home)) "lsp-java/config_linux/")) 
+            (add-to-list 'lsp-java-vmargs "-javaagent:${pkgs.elementary.lombok-jar}/share/java/lombok.jar")
+          '';
         };
         file = {
           ".emacs.d/init.el".source = ./init.el;
           ".emacs.d/early-init.el".text = earlyInitText;
+          ".config/lsp-java/config_linux/config.ini".source = "${pkgs.jdt-language-server}/share/java/jdtls/config_linux/config.ini";
         };
       };
 

modules/nixos/programs/emacs/init.el

@@ -657,6 +657,12 @@
                                        (bound-and-true-p lsp-mode))
                                   (lsp-format-buffer)))))
 
+(use-package lsp-java
+  :init
+  (add-hook 'java-ts-mode-hook . (lambda ()
+                                   (require 'lsp-java)
+                                   (lsp))))
+
 (use-package markdown-mode
   :custom
   (markdown-fontify-code-blocks-natively t)

packages/lombok-jar/default.nix

@@ -0,0 +1,25 @@
+{ lib, stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  pname = "lombok-jar";
+  version = "1.18.30";
+
+  src = fetchurl {
+    url = "https://projectlombok.org/downloads/lombok-${version}.jar";
+    sha256 = "sha256-1+4SLu4erutFGCqJ/zb8LdCGhY0bL1S2Fcb+97odYBI=";
+  };
+
+  buildCommand = ''
+    mkdir -p $out/share/java
+    cp $src $out/share/java/lombok.jar
+  '';
+
+  meta = {
+    description = "A library that can write a lot of boilerplate for your Java project";
+    platforms = lib.platforms.all;
+    sourceProvenance = with lib.sourceTypes; [ binaryBytecode ];
+    license = lib.licenses.mit;
+    homepage = "https://projectlombok.org/";
+    maintainers = [ lib.maintainers.CrystalGamma ];
+  };
+}