Handle future and experimental config keys during upgrade

Author: thecrypticace

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

@@ -411,6 +411,8 @@ function canMigrateConfig(unresolvedConfig: Config, source: string): boolean {
     'presets',
     'prefix', // Prefix is handled in the dedicated prefix migrator
     'corePlugins',
+    'future',
+    'experimental',
   ]
 
   if (Object.keys(unresolvedConfig).some((key) => !knownProperties.includes(key))) {
@@ -425,6 +427,29 @@ function canMigrateConfig(unresolvedConfig: Config, source: string): boolean {
     return false
   }
 
+  // If there are unknown "future" flags we should bail
+  if (unresolvedConfig.future && unresolvedConfig.future !== 'all') {
+    let knownFutureFlags = [
+      'hoverOnlyWhenSupported',
+      'respectDefaultRingColorOpacity',
+      'disableColorOpacityUtilitiesByDefault',
+      'relativeContentPathsByDefault',
+    ]
+
+    if (Object.keys(unresolvedConfig.future).some((key) => !knownFutureFlags.includes(key))) {
+      return false
+    }
+  }
+
+  // If there are unknown "experimental" flags we should bail
+  if (unresolvedConfig.experimental && unresolvedConfig.experimental !== 'all') {
+    let knownFutureFlags = ['generalizedModifiers']
+
+    if (Object.keys(unresolvedConfig.experimental).some((key) => !knownFutureFlags.includes(key))) {
+      return false
+    }
+  }
+
   // Only migrate the config file if all top-level theme keys are allowed to be
   // migrated
   if (theme && typeof theme === 'object') {

packages/tailwindcss/src/compat/config/resolve-config.ts

@@ -33,6 +33,7 @@ interface ResolutionContext {
 let minimal: ResolvedConfig = {
   blocklist: [],
   future: {},
+  experimental: {},
   prefix: '',
   important: false,
   darkMode: null,

packages/tailwindcss/src/compat/config/types.ts

@@ -105,3 +105,12 @@ export interface UserConfig {
 export interface ResolvedConfig {
   future: Record<string, boolean>
 }
+
+// `experimental` key support
+export interface UserConfig {
+  experimental?: 'all' | Record<string, boolean>
+}
+
+export interface ResolvedConfig {
+  experimental: Record<string, boolean>
+}