plugins/cmp/auto-enable: warn if used alongside plugins.*.cmp

Author: MattSturgeon

plugins/cmp/auto-enable.nix

@@ -1,6 +1,7 @@
 {
   lib,
   config,
+  options,
   ...
 }:
 let
@@ -56,9 +57,34 @@ in
   };
 
   config = lib.mkIf (cfg.enable && cfg.autoEnableSources) (
+    let
+      enabledCmpPlugins = builtins.attrNames (
+        lib.filterAttrs (_: plugin: plugin.cmp.enable or false) config.plugins
+      );
+      enabledCmpPluginOpts = builtins.map (
+        # Use the plugin's `enable` option to get the full loc with prefix,
+        # e.g. `programs.nixvim.plugins.foo`
+        name: lib.showOption (lib.dropEnd 1 options.plugins.${name}.enable.loc)
+      ) enabledCmpPlugins;
+    in
     lib.mkMerge [
       {
         warnings = lib.nixvim.mkWarnings "plugins.cmp" [
+          # Warn when the new and old systems are used together.
+          # `autoEnableSources` is incompatible with the new `plugins.*.cmp` options
+          # TODO:
+          # - Have `autoEnableSources` default to no `plugins.*.cmp` options being enabled?
+          # - Maybe warn when `autoEnableSources` has highestPrio 1500?
+          # - I'm not sure how best to migrate to having `plugins.*.cmp.enable` default to true...
+          {
+            when = enabledCmpPlugins != [ ];
+            message = ''
+              You have enabled `autoEnableSources` that tells Nixvim to automatically enable the source plugins with respect to the list of sources provided in `settings.sources`.
+              However, ${builtins.toString (builtins.length enabledCmpPlugins)} plugins have cmp integration configured via `plugins.*.cmp`:${
+                lib.concatStringSep (opt: "\n- `${opt}`") enabledCmpPluginOpts
+              }
+            '';
+          }
           # TODO: expand this warning to ft & cmd sources lists and `showDefs` the offending definitions
           {
             when = lib.types.isRawType cfg.settings.sources;