Fix generation of div:not(.foo) if .foo is never defined

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Correctly parse and prefix animation names with dots ([#7163](https://github.com/tailwindlabs/tailwindcss/pull/7163))
 - Fix extraction from template literal/function with array ([#7481](https://github.com/tailwindlabs/tailwindcss/pull/7481))
 - Don't output unparsable arbitrary values ([#7789](https://github.com/tailwindlabs/tailwindcss/pull/7789))
+- Fix generation of `div:not(.foo)` if `.foo` is never defined ([#7815](https://github.com/tailwindlabs/tailwindcss/pull/7815))
 
 ### Changed
 

src/lib/setupContextUtils.js

@@ -85,12 +85,18 @@ function parseStyles(styles) {
   })
 }
 
-function getClasses(selector) {
+function getClasses(selector, mutate) {
   let parser = selectorParser((selectors) => {
     let allClasses = []
+
+    if (mutate) {
+      mutate(selectors)
+    }
+
     selectors.walkClasses((classNode) => {
       allClasses.push(classNode.value)
     })
+
     return allClasses
   })
   return parser.transformSync(selector)
@@ -101,8 +107,20 @@ function extractCandidates(node, state = { containsNonOnDemandable: false }, dep
 
   // Handle normal rules
   if (node.type === 'rule') {
+    // Ignore everything inside a :not(...). This allows you to write code like
+    // `div:not(.foo)`. If `.foo` is never found in your code, then we used to
+    // not generated it. But now we will ignore everything inside a `:not`, so
+    // that it still gets generated.
+    function ignoreNot(selectors) {
+      selectors.walkPseudos((pseudo) => {
+        if (pseudo.value === ':not') {
+          pseudo.remove()
+        }
+      })
+    }
+
     for (let selector of node.selectors) {
-      let classCandidates = getClasses(selector)
+      let classCandidates = getClasses(selector, ignoreNot)
       // At least one of the selectors contains non-"on-demandable" candidates.
       if (classCandidates.length === 0) {
         state.containsNonOnDemandable = true
@@ -117,9 +135,7 @@ function extractCandidates(node, state = { containsNonOnDemandable: false }, dep
   // Handle at-rules (which contains nested rules)
   else if (node.type === 'atrule') {
     node.walkRules((rule) => {
-      for (let classCandidate of rule.selectors.flatMap((selector) =>
-        getClasses(selector, state, depth + 1)
-      )) {
+      for (let classCandidate of rule.selectors.flatMap((selector) => getClasses(selector))) {
         classes.push(classCandidate)
       }
     })

tests/basic-usage.test.js

@@ -349,7 +349,7 @@ it('does not produce duplicate output when seeing variants preceding a wildcard
   })
 })
 
-it('it can parse box shadows with variables', () => {
+it('can parse box shadows with variables', () => {
   let config = {
     content: [{ raw: html`<div class="shadow-lg"></div>` }],
     theme: {
@@ -376,3 +376,28 @@ it('it can parse box shadows with variables', () => {
     `)
   })
 })
+
+it('should generate styles using :not(.unknown-class) even if `.unknown-class` does not exist', () => {
+  let config = {
+    content: [{ raw: html`<div></div>` }],
+    corePlugins: { preflight: false },
+  }
+
+  let input = css`
+    @tailwind components;
+
+    @layer components {
+      div:not(.unknown-class) {
+        color: red;
+      }
+    }
+  `
+
+  return run(input, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(css`
+      div:not(.unknown-class) {
+        color: red;
+      }
+    `)
+  })
+})