lsp/null-lsp: allow null-ls options to be configured

This should probably still be converted to setupOpts. Missing docs

modules/plugins/lsp/null-ls/config.nix

@@ -5,6 +5,7 @@
 }: let
   inherit (lib.modules) mkIf mkMerge;
   inherit (lib.attrsets) mapAttrs;
+  inherit (lib.trivial) boolToString;
   inherit (lib.nvim.dag) entryAnywhere entryAfter entryBetween;
 
   cfg = config.vim.lsp;
@@ -12,26 +13,36 @@ in {
   config = mkIf cfg.null-ls.enable (mkMerge [
     {
       vim = {
+        startPlugins = [
+          "none-ls"
+          "plenary-nvim"
+        ];
+
+        # null-ls implies LSP already being set up
+        # since it will hook into LSPs to receive information
         lsp.enable = true;
-        startPlugins = ["none-ls"];
 
-        luaConfigRC.null_ls-setup = entryAnywhere ''
-          local null_ls = require("null-ls")
-          local null_helpers = require("null-ls.helpers")
-          local null_methods = require("null-ls.methods")
-          local ls_sources = {}
-        '';
+        luaConfigRC = {
+          # early setup for null-ls
+          null_ls-setup = entryAnywhere ''
+            local null_ls = require("null-ls")
+            local null_helpers = require("null-ls.helpers")
+            local null_methods = require("null-ls.methods")
+            local ls_sources = {}
+          '';
 
-        luaConfigRC.null_ls = entryAfter ["null_ls-setup" "lsp-setup"] ''
-          require('null-ls').setup({
-            debug = false,
-            diagnostics_format = "[#{m}] #{s} (#{c})",
-            debounce = 250,
-            default_timeout = 5000,
-            sources = ls_sources,
-            on_attach = default_on_attach
-          })
-        '';
+          # null-ls setup
+          null_ls = entryAfter ["null_ls-setup" "lsp-setup"] ''
+            require('null-ls').setup({
+              debug = ${boolToString cfg.null-ls.debug},
+              diagnostics_format = "${cfg.null-ls.diagnostics_format}",
+              debounce = ${toString cfg.null-ls.debounce},
+              default_timeout = ${toString cfg.null-ls.default_timeout},
+              sources = ls_sources,
+              on_attach = default_on_attach
+            })
+          '';
+        };
       };
     }
     {

modules/plugins/lsp/null-ls/null-ls.nix

@@ -1,10 +1,32 @@
 {lib, ...}: let
   inherit (lib.options) mkEnableOption mkOption;
-  inherit (lib.types) attrsOf str;
+  inherit (lib.types) attrsOf str int;
+  inherit (lib.generators) mkLuaInline;
+  inherit (lib.nvim.types) luaInline;
 in {
   options.vim.lsp.null-ls = {
     enable = mkEnableOption "null-ls, also enabled automatically";
 
+    debug = mkEnableOption "debugging information for `null-ls";
+
+    diagnostics_format = mkOption {
+      type = luaInline;
+      default = mkLuaInline "[#{m}] #{s} (#{c})";
+      description = "Diagnostic output format for null-ls";
+    };
+
+    debounce = mkOption {
+      type = int;
+      default = 250;
+      description = "Default debounce";
+    };
+
+    default_timeout = mkOption {
+      type = int;
+      default = 5000;
+      description = "Default timeout value, in miliseconds";
+    };
+
     sources = mkOption {
       description = "null-ls sources";
       type = attrsOf str;