languages/java: add dap support via JLS

modules/plugins/languages/go.nix

@@ -205,7 +205,7 @@ in {
 
     dap = {
       enable =
-        mkEnableOption "Go Debug Adapter (DAP) via `nvim-dap-go"
+        mkEnableOption "Go Debug Adapter"
         // {
           default = config.vim.languages.enableDAP;
           defaultText = literalExpression "config.vim.languages.enableDAP";

modules/plugins/languages/java.nix

@@ -2,19 +2,47 @@
   config,
   pkgs,
   lib,
+  inputs,
   ...
 }: let
-  inherit (lib.options) literalExpression mkEnableOption mkOption;
   inherit (lib.modules) mkIf mkMerge;
-  inherit (lib) genAttrs;
-  inherit (lib.types) listOf str;
-  inherit (lib.meta) getExe;
+  inherit (lib.options) literalExpression mkEnableOption mkOption;
+  inherit (lib.types) listOf str enum package;
+  inherit (lib.attrsets) attrNames genAttrs;
+  inherit (lib.meta) getExe getExe';
   inherit (lib.nvim.types) mkGrammarOption mkPluginSetupOption enumWithRename;
 
   cfg = config.vim.languages.java;
 
   defaultServers = ["jdt-language-server"];
   servers = ["jdt-language-server" "jls"];
+
+  defaultDebugger = "jls";
+  debuggers = {
+    jls = let
+      pkg = inputs.self.packages.${pkgs.stdenv.hostPlatform.system}.jls;
+    in {
+      package = pkg;
+      config =
+        # Lua
+        ''
+          dap.adapters.jls= {
+            type = 'executable',
+            command = '${getExe' pkg "jls-dap"}',
+          }
+          dap.configurations.java = {
+            {
+              type = "jls",
+              request = "attach",
+              name = "Attach",
+              hostName = "localhost",
+              port = 5005,
+              sourceRoots = vim.fn.glob("**/src/main/java", true, true),
+            },
+          }
+        '';
+    };
+  };
 in {
   options.vim.languages.java = {
     enable = mkEnableOption "Java language support";
@@ -48,6 +76,72 @@ in {
       };
     };
 
+    dap = {
+      enable =
+        mkEnableOption "Java Debug Adapter"
+        // {
+          default = config.vim.languages.enableDAP;
+          defaultText = literalExpression "config.vim.languages.enableDAP";
+        };
+
+      debugger = mkOption {
+        type = enum (attrNames debuggers);
+        default = defaultDebugger;
+        description = ''
+          Java debugger to use.
+
+          **JLS**
+
+          For `jls` to work, you need to run your application with debug symbols and networking.
+
+          The `jls` configuration is hardcoded to listen on port `5005`.
+          This matches the configuration described [upstream](https://github.com/idelice/jls#usage).
+          You can change this by modifying `vim.debugger.nvim-dap.sources.java-debugger`.
+          ```nix
+          vim.debugger.nvim-dap.sources.java-debugger = /* lua */ '''
+            dap.adapters.jls= {
+              type = 'executable',
+              command = ''\'''${getExe' inputs.self.packages.''${pkgs.stdenv.hostPlatform.system}.jls "jls-dap"}',
+            }
+            dap.configurations.java = {
+              {
+                type = "jls",
+                request = "attach",
+                name = "Attach",
+                hostName = "localhost",
+                port = 6969, -- your custom port
+                sourceRoots = vim.fn.glob("**/src/main/java", true, true),
+              },
+            }
+          ''';
+          ```
+
+          *Examples:*
+
+          - Manual:
+            1. Build with debug symbols.
+               ```sh
+               javac -g ...
+               ```
+            1. Run with debug socket.
+               ```sh
+               java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -jar your.jar
+               ```
+          - Springboot Maven:
+            For Springboot you can just pass the JVM args directly into the `spring-boot:run`.
+            ```sh
+            mvn spring-boot:run -Dspring-boot.run.jvmArguments="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
+            ```
+        '';
+      };
+
+      package = mkOption {
+        type = package;
+        default = debuggers.${cfg.dap.debugger}.package;
+        description = "Java debugger package.";
+      };
+    };
+
     extensions = {
       maven-nvim = {
         enable = mkEnableOption "maven integration";
@@ -88,6 +182,11 @@ in {
   };
 
   config = mkIf cfg.enable (mkMerge [
+    (mkIf cfg.treesitter.enable {
+      vim.treesitter.enable = true;
+      vim.treesitter.grammars = [cfg.treesitter.package];
+    })
+
     (mkIf cfg.lsp.enable {
       vim.lsp = {
         presets = genAttrs cfg.lsp.servers (_: {enable = true;});
@@ -97,9 +196,11 @@ in {
       };
     })
 
-    (mkIf cfg.treesitter.enable {
-      vim.treesitter.enable = true;
-      vim.treesitter.grammars = [cfg.treesitter.package];
+    (mkIf cfg.dap.enable {
+      vim.debugger.nvim-dap = {
+        enable = true;
+        sources.java-debugger = debuggers.${cfg.dap.debugger}.config;
+      };
     })
 
     (mkIf cfg.extensions.maven-nvim.enable {