Fix wildcard duplication issue (#7478)

This would be better as a symbol but the stringy-ness of class candidates is fairly well baked into assumptions across the codebase. Using `new String` with a well placed check seems to solve the problem.

src/lib/expandTailwindAtRules.js

@@ -158,7 +158,7 @@ export default function expandTailwindAtRules(context) {
     // ---
 
     // Find potential rules in changed files
-    let candidates = new Set(['*'])
+    let candidates = new Set([sharedState.NOT_ON_DEMAND])
     let seen = new Set()
 
     env.DEBUG && console.time('Reading changed files')

src/lib/generateRules.js

@@ -5,6 +5,7 @@ import isPlainObject from '../util/isPlainObject'
 import prefixSelector from '../util/prefixSelector'
 import { updateAllClasses } from '../util/pluginUtils'
 import log from '../util/log'
+import * as sharedState from './sharedState'
 import { formatVariantSelector, finalizeSelector } from '../util/formatVariantSelector'
 import { asClass } from '../util/nameClass'
 import { normalize } from '../util/dataTypes'
@@ -382,6 +383,10 @@ function* resolveMatchedPlugins(classCandidate, context) {
 }
 
 function splitWithSeparator(input, separator) {
+  if (input === sharedState.NOT_ON_DEMAND) {
+    return [sharedState.NOT_ON_DEMAND]
+  }
+
   return input.split(new RegExp(`\\${separator}(?![^[]*\\])`, 'g'))
 }
 

src/lib/setupContextUtils.js

@@ -138,7 +138,7 @@ function withIdentifiers(styles) {
 
     // If this isn't "on-demandable", assign it a universal candidate to always include it.
     if (containsNonOnDemandableSelectors) {
-      candidates.unshift('*')
+      candidates.unshift(sharedState.NOT_ON_DEMAND)
     }
 
     // However, it could be that it also contains "on-demandable" candidates.
@@ -163,8 +163,8 @@ function buildPluginApi(tailwindConfig, context, { variantList, variantMap, offs
   }
 
   function prefixIdentifier(identifier, options) {
-    if (identifier === '*') {
-      return '*'
+    if (identifier === sharedState.NOT_ON_DEMAND) {
+      return sharedState.NOT_ON_DEMAND
     }
 
     if (!options.respectPrefix) {

src/lib/sharedState.js

@@ -5,6 +5,7 @@ export const env = {
 export const contextMap = new Map()
 export const configContextMap = new Map()
 export const contextSourcesMap = new Map()
+export const NOT_ON_DEMAND = new String('*')
 
 export function resolveDebug(debug) {
   if (debug === undefined) {