fix: fixed merging of unsupported pseudos by caniuse and browserlist

packages/cssnano/src/__tests__/postcss-merge-rules.js

@@ -1,4 +1,4 @@
-import processCss from './_processCss';
+import processCss, { passthrough } from './_processCss';
 
 test(
   'should merge based on declarations',
@@ -183,9 +183,8 @@ test(
 
 test(
   'should merge vendor prefixed selectors when vendors are the same',
-  processCss(
-    'code ::-moz-selection{background:red}code::-moz-selection{background:red}',
-    'code::-moz-selection,code ::-moz-selection{background:red}'
+  passthrough(
+    'code ::-moz-selection{background:red}code::-moz-selection{background:red}'
   )
 );
 

packages/postcss-merge-rules/src/__tests__/index.js

@@ -251,9 +251,20 @@ test(
 
 test(
   'should merge vendor prefixed selectors when vendors are the same',
-  processCSS(
-    'code ::-moz-selection{background:red}code::-moz-selection{background:red}',
-    'code ::-moz-selection,code::-moz-selection{background:red}'
+  passthroughCSS(
+    'code ::-moz-selection{background:red}code::-moz-selection{background:red}'
+  )
+);
+
+test(
+  'should not merge pseudo which are not supported by the browsers ::selection',
+  passthroughCSS('::selection{background:red} ::selection{background:red}')
+);
+
+test(
+  'should not merge pseudo which are not supported by the browsers - code ::selection',
+  passthroughCSS(
+    'code ::selection{background:red} code ::selection{background:red}'
   )
 );
 

packages/postcss-merge-rules/src/lib/ensureCompatibility.js

@@ -1,3 +1,4 @@
+import postcss from 'postcss';
 import { isSupported } from 'caniuse-api';
 import selectorParser from 'postcss-selector-parser';
 
@@ -55,6 +56,7 @@ export const pseudoElements = {
   '::marker': 'css-marker-pseudo',
   '::placeholder': 'css-placeholder',
   '::selection': 'css-selection',
+  ':visited': cssSel3,
 };
 
 function isCssMixin(selector) {
@@ -97,8 +99,10 @@ export default function ensureCompatibility(
       ast.walk((node) => {
         const { type, value } = node;
         if (type === 'pseudo') {
-          const entry = pseudoElements[value];
-          if (entry && compatible) {
+          const entry = pseudoElements[postcss.vendor.unprefixed(value)];
+          if (!entry) {
+            compatible = false;
+          } else if (compatible) {
             compatible = isSupportedCached(entry, browsers);
           }
         }