Allow users to block generation of certain utilities (#9812)

* Add blocklist tests

* Build initial implementation of blocklist

* wip

* wip

* wip

* Update changelog

src/lib/setupContextUtils.js

@@ -1165,7 +1165,8 @@ export function createContext(tailwindConfig, changedContent = [], root = postcs
     candidateRuleCache: new Map(),
     classCache: new Map(),
     applyClassCache: new Map(),
-    notClassCache: new Set(),
+    // Seed the not class cache with the blocklist (which is only strings)
+    notClassCache: new Set(tailwindConfig.blocklist ?? []),
     postCssNodeCache: new Map(),
     candidateRuleMap: new Map(),
     tailwindConfig,

src/util/normalizeConfig.js

@@ -150,6 +150,24 @@ export function normalizeConfig(config) {
     return []
   })()
 
+  // Normalize the `blocklist`
+  config.blocklist = (() => {
+    let { blocklist } = config
+
+    if (Array.isArray(blocklist)) {
+      if (blocklist.every((item) => typeof item === 'string')) {
+        return blocklist
+      }
+
+      log.warn('blocklist-invalid', [
+        'The `blocklist` option must be an array of strings.',
+        'https://tailwindcss.com/docs/content-configuration#discarding-classes',
+      ])
+    }
+
+    return []
+  })()
+
   // Normalize prefix option
   if (typeof config.prefix === 'function') {
     log.warn('prefix-function', [