Fix Plugin type issue (#14668)

This is a quick fix to an issue where the types for PluginsConfig don't
match those used in plugins like
[`@tailwindcss/container-queries`](https://github.com/tailwindlabs/tailwindcss-container-queries).

This was caught by TypeScript with [`exactOptionalPropertyTypes`](
https://www.typescriptlang.org/tsconfig/exactOptionalPropertyTypes.html)
enabled, where TypeScript checks if `undefined` can be supplied as a
value for optional types.

I felt that it made more sense to fix this here, as it makes the core
types more flexible, as opposed to each plugin needing to fix this
when/if they hit it.

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet!
+### Fixed
+
+- Ensure the TypeScript types for `PluginsConfig` allow `undefined` values ([#14668](https://github.com/tailwindlabs/tailwindcss/pull/14668))
 
 ## [3.4.15] - 2024-11-14
 

types/config.d.ts

@@ -344,9 +344,12 @@ export interface PluginAPI {
 export type PluginCreator = (api: PluginAPI) => void
 export type PluginsConfig = (
   | PluginCreator
-  | { handler: PluginCreator; config?: Partial<Config> }
+  | { handler: PluginCreator; config?: Partial<Config> | undefined }
   | {
-      (options: any): { handler: PluginCreator; config?: Partial<Config> }
+      (options: any): {
+        handler: PluginCreator;
+        config?: Partial<Config> | undefined;
+      };
       __isOptionsFunction: true
     }
 )[]