languages/scala: Add scala language support (#399)

* languages/scala: Add scala language support

Adds LSP support for Scala via nvim-metals

* Fix luaInline import

* Add changelog entry for Scala support to 0.7 release notes

---------

Co-authored-by: raf <[email protected]>

configuration.nix

@@ -69,6 +69,7 @@ isMaximal: {
         lsp.server = "clangd";
       };
 
+      scala.enable = isMaximal;
       rust = {
         enable = isMaximal;
         crates.enable = isMaximal;

docs/release-notes/rl-0.7.md

@@ -267,3 +267,7 @@ everyone.
 - Add support for [base16 theming](https://github.com/RRethy/base16-nvim) under
   `vim.theme`
 - Fix internal breakage in `elixir-tools` setup.
+
+[ksonj](https://github.com/ksonj):
+
+- Add LSP support for Scala via [nvim-metals](https://github.com/scalameta/nvim-metals)

flake.nix

@@ -206,6 +206,11 @@
       flake = false;
     };
 
+    plugin-nvim-metals = {
+      url = "github:scalameta/nvim-metals";
+      flake = false;
+    };
+
     # Copying/Registers
     plugin-registers = {
       url = "github:tversteeg/registers.nvim";

modules/plugins/languages/default.nix

@@ -20,6 +20,7 @@ in {
     ./python.nix
     ./r.nix
     ./rust.nix
+    ./scala.nix
     ./sql.nix
     ./svelte.nix
     ./tailwind.nix

modules/plugins/languages/scala.nix

@@ -0,0 +1,149 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  inherit (lib.generators) mkLuaInline;
+  inherit (lib.modules) mkIf mkMerge;
+  inherit (lib.nvim.binds) mkMappingOption;
+  inherit (lib.nvim.dag) entryAfter;
+  inherit (lib.nvim.lua) toLuaObject;
+  inherit (lib.nvim.types) mkGrammarOption luaInline;
+  inherit (lib.options) mkOption mkEnableOption mkPackageOption;
+  inherit (lib.strings) optionalString;
+  inherit (lib.types) attrsOf anything bool;
+
+  listCommandsAction =
+    if config.vim.telescope.enable
+    then ''require("telescope").extensions.metals.commands()''
+    else ''require("metals").commands()'';
+
+  cfg = config.vim.languages.scala;
+
+  usingDap = config.vim.debugger.nvim-dap.enable && cfg.dap.enable;
+  usingLualine = config.vim.statusline.lualine.enable;
+in {
+  options.vim.languages.scala = {
+    enable = mkEnableOption "Scala language support";
+
+    treesitter = {
+      enable = mkEnableOption "Scala treesitter" // {default = config.vim.languages.enableTreesitter;};
+      package = mkGrammarOption pkgs "scala";
+    };
+
+    lsp = {
+      enable = mkEnableOption "Scala LSP support (metals)" // {default = config.vim.languages.enableLSP;};
+      package = mkPackageOption pkgs "metals" {
+        default = ["metals"];
+      };
+
+      extraMappings = {
+        listCommands = mkMappingOption "List Metals commands" "<leader>lc";
+      };
+
+      extraSettings = mkOption {
+        type = attrsOf anything;
+        description = "Extra settings passed to the metals config. Check nvim-metals docs for available options";
+        default = {
+          showImplicitArguments = true;
+          showImplicitConversionsAndClasses = true;
+          showInferredType = true;
+          excludedPackages = [
+            "akka.actor.typed.javadsl"
+            "com.github.swagger.akka.javadsl"
+          ];
+        };
+      };
+    };
+
+    dap = {
+      enable = mkEnableOption "Scala Debug Adapter support (metals)" // {default = config.vim.languages.enableDAP;};
+      config = mkOption {
+        description = "Lua configuration for dap";
+        type = luaInline;
+        default = mkLuaInline ''
+          dap.configurations.scala = {
+            {
+              type = "scala",
+              request = "launch",
+              name = "RunOrTest",
+              metals = {
+                runType = "runOrTestFile",
+                --args = { "firstArg", "secondArg", "thirdArg" }, -- here just as an example
+              },
+            },
+            {
+              type = "scala",
+              request = "launch",
+              name = "Test Target",
+              metals = {
+                runType = "testTarget",
+              },
+            },
+          }
+        '';
+      };
+    };
+
+    fixShortmess = mkOption {
+      type = bool;
+      description = "Remove the 'F' flag from shortmess to allow messages to be shown. Without doing this, autocommands that deal with filetypes prohibit messages from being shown";
+      default = true;
+    };
+  };
+
+  config = mkIf cfg.enable (
+    mkMerge [
+      (mkIf cfg.treesitter.enable {
+        vim.treesitter.enable = true;
+        vim.treesitter.grammars = [cfg.treesitter.package];
+      })
+      (mkIf (cfg.lsp.enable || cfg.dap.enable) {
+        vim = {
+          startPlugins = ["nvim-metals"];
+          pluginRC.nvim-metals = entryAfter ["lsp-setup"] ''
+            local metals_caps = capabilities  -- from lsp-setup
+
+            local attach_metals_keymaps = function(client, bufnr)
+              attach_keymaps(client, bufnr)  -- from lsp-setup
+              vim.api.nvim_buf_set_keymap(bufnr, 'n', '${cfg.lsp.extraMappings.listCommands}', '<cmd>lua ${listCommandsAction}<CR>', {noremap=true, silent=true, desc='Show all Metals commands'})
+            end
+
+            metals_config = require('metals').bare_config()
+            ${optionalString usingLualine "metals_config.init_options.statusBarProvider = 'on'"}
+
+            metals_config.capabilities = metals_caps
+            metals_config.on_attach = function(client, bufnr)
+              ${optionalString usingDap "require('metals').setup_dap()"}
+              attach_metals_keymaps(client, bufnr)
+            end
+
+            metals_config.settings = ${toLuaObject cfg.lsp.extraSettings}
+            metals_config.settings.metalsBinaryPath = "${cfg.lsp.package}/bin/metals"
+
+            metals_config.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(
+              vim.lsp.diagnostic.on_publish_diagnostics, {
+                virtual_text = {
+                  prefix = '⚠',
+                }
+              }
+            )
+
+            ${optionalString cfg.fixShortmess ''vim.opt_global.shortmess:remove("F")''}
+
+            local lsp_group = vim.api.nvim_create_augroup('lsp', { clear = true })
+
+            vim.api.nvim_create_autocmd('FileType', {
+                group = lsp_group,
+                pattern = {'java', 'scala', 'sbt'},
+                callback = function()
+                    require('metals').initialize_or_attach(metals_config)
+                end,
+            })
+          '';
+        };
+      })
+    ]
+  );
+}