modules/diagnostic: rename diagnostics -> diagnostic.config

Currently we represent `vim.diagnostic.config()` as a top-level
`diagnostics` option. This means we have no clear namespace for
(e.g.) `vim.diagnostic.<action>` keymap functions.

Author: MattSturgeon

modules/default.nix

@@ -10,7 +10,7 @@
     ./colorscheme.nix
     ./commands.nix
     ./dependencies.nix
-    ./diagnostics.nix
+    ./diagnostic.nix
     ./doc.nix
     ./editorconfig.nix
     ./files.nix

modules/diagnostic.nix

@@ -0,0 +1,32 @@
+{
+  lib,
+  config,
+  ...
+}:
+let
+  cfg = config.diagnostic;
+in
+{
+  options.diagnostic = {
+    config = lib.mkOption {
+      type = with lib.types; attrsOf anything;
+      default = { };
+      description = "The configuration diagnostic options, provided to `vim.diagnostic.config`.";
+      example = {
+        virtual_text = false;
+        virtual_lines.current_line = true;
+      };
+    };
+  };
+
+  imports = [
+    # TODO: Added 2025-04-26; remove after 25.05
+    (lib.mkRenamedOptionModule [ "diagnostics" ] [ "diagnostic" "config" ])
+  ];
+
+  config = {
+    extraConfigLuaPre = lib.mkIf (cfg.config != { }) ''
+      vim.diagnostic.config(${lib.nixvim.toLuaObject cfg.config})
+    '';
+  };
+}

modules/diagnostics.nix

@@ -24,7 +24,8 @@ lib.nixvim.plugins.mkNeovimPlugin {
         "currentLine"
       ]
       [
-        "diagnostics"
+        "diagnostic"
+        "config"
         "virtual_lines"
         "only_current_line"
       ]
@@ -33,6 +34,6 @@ lib.nixvim.plugins.mkNeovimPlugin {
 
   extraConfig = {
     # Strongly recommended by the plugin, to avoid duplication.
-    diagnostics.virtual_text = mkDefault false;
+    diagnostic.config.virtual_text = mkDefault false;
   };
 }

plugins/by-name/lsp-lines/default.nix

@@ -1,6 +1,6 @@
 {
   example = {
-    diagnostics = {
+    diagnostic.config = {
       virtual_text = false;
       virtual_lines.current_line = true;
     };

tests/test-sources/modules/diagnostics.nix

@@ -6,7 +6,7 @@
   example = {
     plugins.lsp-lines.enable = true;
 
-    diagnostics.virtual_lines = {
+    diagnostic.config.virtual_lines = {
       only_current_line = true;
       highlight_whole_line = false;
     };