feat(selectors): optimize old->new selectors conversion for text (#4671)

Author: dgozman

src/server/common/cssParser.ts

@@ -16,7 +16,8 @@
 
 import * as css from './cssTokenizer';
 
-type ClauseCombinator = '' | '>' | '+' | '~';
+// Note: '>=' is used internally for text engine to preserve backwards compatibility.
+type ClauseCombinator = '' | '>' | '+' | '~' | '>=';
 // TODO: consider
 //   - key=value
 //   - operators like `=`, `|=`, `~=`, `*=`, `/`

src/server/common/selectorParser.ts

@@ -55,7 +55,7 @@ export function parseSelector(selector: string, customNames: Set<string>): Parse
   }
 
   const chain = (from: number, to: number): CSSComplexSelector => {
-    let result: CSSComplexSelector = { simples: [] };
+    const result: CSSComplexSelector = { simples: [] };
     for (const part of v1.parts.slice(from, to)) {
       let name = part.name;
       let wrapInLight = false;
@@ -70,24 +70,14 @@ export function parseSelector(selector: string, customNames: Set<string>): Parse
         simple = callWith('is', parsed.selector);
       } else if (name === 'text') {
         simple = textSelectorToSimple(part.body);
+        if (result.simples.length)
+          result.simples[result.simples.length - 1].combinator = '>=';
       } else {
         simple = callWith(name, [part.body]);
       }
       if (wrapInLight)
         simple = callWith('light', [simpleToComplex(simple)]);
-      if (name === 'text') {
-        const copy = result.simples.map(one => {
-          return { selector: copySimple(one.selector), combinator: one.combinator };
-        });
-        copy.push({ selector: simple, combinator: '' });
-        if (!result.simples.length)
-          result.simples.push({ selector: callWith('scope', []), combinator: '' });
-        const last = result.simples[result.simples.length - 1];
-        last.selector.functions.push({ name: 'is', args: [simpleToComplex(simple)] });
-        result = simpleToComplex(callWith('is', [{ simples: copy }, result]));
-      } else {
-        result.simples.push({ selector: simple, combinator: '' });
-      }
+      result.simples.push({ selector: simple, combinator: '' });
     }
     return result;
   };
@@ -110,10 +100,6 @@ function simpleToComplex(simple: CSSSimpleSelector): CSSComplexSelector {
   return { simples: [{ selector: simple, combinator: '' }]};
 }
 
-function copySimple(simple: CSSSimpleSelector): CSSSimpleSelector {
-  return { css: simple.css, functions: simple.functions.slice() };
-}
-
 function textSelectorToSimple(selector: string): CSSSimpleSelector {
   function unescape(s: string): string {
     if (!s.includes('\\'))

src/server/injected/selectorEvaluator.ts

@@ -214,6 +214,19 @@ export class SelectorEvaluatorImpl implements SelectorEvaluator {
         }
         return false;
       }
+      if (combinator === '>=') {
+        let parent: Element | undefined = element;
+        while (parent) {
+          if (this._matchesSimple(parent, simple, context)) {
+            if (this._matchesParents(parent, complex, index - 1, context))
+              return true;
+            if (complex.simples[index - 1].combinator === '')
+              break;
+          }
+          parent = parentElementOrShadowHostInContext(parent, context);
+        }
+        return false;
+      }
       throw new Error(`Unsupported combinator "${combinator}"`);
     });
   }