Upgrade: Allow corePlugins in JS config files (#14742)

This PR enables JS configuration files with `corePlugins` themes to be
migrated. If such option is found in your config, we will warn the user
and omit the option from the resulting CSS file as there is no v4
alternative.

---------

Co-authored-by: Adam Wathan <adam.wathan@gmail.com>

Author: philipp-spiess

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - _Upgrade (experimental)_: Migrate `plugins` with options to CSS ([#14700](https://github.com/tailwindlabs/tailwindcss/pull/14700))
+- _Upgrade (experimental)_: Allow JS configuration files with `corePlugins` options to be migrated to CSS ([#14742](https://github.com/tailwindlabs/tailwindcss/pull/14742))
 
 ### Fixed
 

packages/@tailwindcss-upgrade/src/migrate-js-config.ts

@@ -63,6 +63,12 @@ export async function migrateJsConfig(
     if (themeConfig) cssConfigs.push(themeConfig)
   }
 
+  if ('corePlugins' in unresolvedConfig) {
+    info(
+      `The \`corePlugins\` option is no longer supported as of Tailwind CSS v4.0, so it's been removed from your configuration.`,
+    )
+  }
+
   let simplePlugins = findStaticPlugins(source)
   if (simplePlugins !== null) {
     for (let [path, options] of simplePlugins) {
@@ -214,6 +220,7 @@ function canMigrateConfig(unresolvedConfig: Config, source: string): boolean {
     'plugins',
     'presets',
     'prefix', // Prefix is handled in the dedicated prefix migrator
+    'corePlugins',
   ]
 
   if (Object.keys(unresolvedConfig).some((key) => !knownProperties.includes(key))) {