feat(selectors): introduce css evaluator (#4573)

Not used for production yet.

src/debug/injected/debugScript.webpack.config.js

@@ -23,7 +23,7 @@ module.exports = {
   module: {
     rules: [
       {
-        test: /\.tsx?$/,
+        test: /\.(j|t)sx?$/,
         loader: 'ts-loader',
         options: {
           transpileOnly: true

src/server/common/cssParser.ts

@@ -24,10 +24,10 @@ type ClauseCombinator = '' | '>' | '+' | '~';
 export type CSSFunctionArgument = CSSComplexSelector | number | string;
 export type CSSFunction = { name: string, args: CSSFunctionArgument[] };
 export type CSSSimpleSelector = { css?: string, functions: CSSFunction[] };
-export type CSSComplexSelector = { simple: { selector: CSSSimpleSelector, combinator: ClauseCombinator }[] };
+export type CSSComplexSelector = { simples: { selector: CSSSimpleSelector, combinator: ClauseCombinator }[] };
-export type CSSSelectorList = CSSComplexSelector[];
+export type CSSComplexSelectorList = CSSComplexSelector[];
 
-export function parseCSS(selector: string): CSSSelectorList {
+export function parseCSS(selector: string): CSSComplexSelectorList {
   let tokens: css.CSSTokenInterface[];
   try {
     tokens = css.tokenize(selector);
@@ -131,16 +131,16 @@ export function parseCSS(selector: string): CSSSelectorList {
 
   function consumeComplexSelector(): CSSComplexSelector {
     skipWhitespace();
-    const result = { simple: [{ selector: consumeSimpleSelector(), combinator: '' as ClauseCombinator }] };
+    const result = { simples: [{ selector: consumeSimpleSelector(), combinator: '' as ClauseCombinator }] };
     while (true) {
       skipWhitespace();
       if (isClauseCombinator()) {
-        result.simple[result.simple.length - 1].combinator = tokens[pos++].value as ClauseCombinator;
+        result.simples[result.simples.length - 1].combinator = tokens[pos++].value as ClauseCombinator;
         skipWhitespace();
       } else if (isSelectorClauseEnd()) {
         break;
       }
-      result.simple.push({ combinator: '', selector: consumeSimpleSelector() });
+      result.simples.push({ combinator: '', selector: consumeSimpleSelector() });
     }
     return result;
   }
@@ -163,12 +163,12 @@ export function parseCSS(selector: string): CSSSelectorList {
       } else if (tokens[pos] instanceof css.ColonToken) {
         pos++;
         if (isIdent()) {
-          if (builtinCSSFilters.has(tokens[pos].value))
+          if (builtinCSSFilters.has(tokens[pos].value.toLowerCase()))
             rawCSSString += ':' + tokens[pos++].toSource();
           else
-            functions.push({ name: tokens[pos++].value, args: [] });
+            functions.push({ name: tokens[pos++].value.toLowerCase(), args: [] });
         } else if (tokens[pos] instanceof css.FunctionToken) {
-          const name = tokens[pos++].value;
+          const name = tokens[pos++].value.toLowerCase();
           if (builtinCSSFunctions.has(name))
             rawCSSString += `:${name}(${consumeBuiltinFunctionArguments()})`;
           else
@@ -208,7 +208,7 @@ export function parseCSS(selector: string): CSSSelectorList {
   const result = consumeFunctionArguments();
   if (!isEOF())
     throw new Error(`Error while parsing selector "${selector}"`);
-  if (result.some(arg => typeof arg !== 'object' || !('simple' in arg)))
+  if (result.some(arg => typeof arg !== 'object' || !('simples' in arg)))
     throw new Error(`Error while parsing selector "${selector}"`);
   return result as CSSComplexSelector[];
 }
@@ -219,7 +219,7 @@ export function serializeSelector(args: CSSFunctionArgument[]) {
       return `"${arg}"`;
     if (typeof arg === 'number')
       return String(arg);
-    return arg.simple.map(({ selector, combinator }) => {
+    return arg.simples.map(({ selector, combinator }) => {
       let s = selector.css || '';
       s = s + selector.functions.map(func => `:${func.name}(${serializeSelector(func.args)})`).join('');
       if (combinator)

src/server/injected/injectedScript.webpack.config.js

@@ -23,7 +23,7 @@ module.exports = {
   module: {
     rules: [
       {
-        test: /\.tsx?$/,
+        test: /\.(j|t)sx?$/,
         loader: 'ts-loader',
         options: {
           transpileOnly: true

src/server/injected/selectorEvaluator.ts

@@ -0,0 +1,378 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { CSSComplexSelector, CSSSimpleSelector, CSSComplexSelectorList, CSSFunctionArgument } from '../common/cssParser';
+
+export type QueryContext = {
+  scope: Element | ShadowRoot | Document;
+  // Place for more options, e.g. normalizing whitespace or piercing shadow.
+};
+export type Selector = any; // Opaque selector type.
+export interface SelectorEvaluator {
+  query(context: QueryContext, selector: Selector): Element[];
+  matches(element: Element, selector: Selector, context: QueryContext): boolean;
+}
+export interface SelectorEngine {
+  matches?(element: Element, args: (string | number | Selector)[], context: QueryContext, evaluator: SelectorEvaluator): boolean;
+  query?(context: QueryContext, args: (string | number | Selector)[], evaluator: SelectorEvaluator): Element[];
+}
+
+export class SelectorEvaluatorImpl implements SelectorEvaluator {
+  private _engines = new Map<string, SelectorEngine>();
+  private _cache = new Map<any, { rest: any[], result: any }[]>();
+
+  constructor(extraEngines: Map<string, SelectorEngine>) {
+    for (const [name, engine] of extraEngines)
+      this._engines.set(name, engine);
+    this._engines.set('not', notEngine);
+    this._engines.set('is', isEngine);
+    this._engines.set('where', isEngine);
+    this._engines.set('has', hasEngine);
+    this._engines.set('scope', scopeEngine);
+    // TODO: host
+    // TODO: host-context?
+  }
+
+  // This is the only function we should use for querying, because it does
+  // the right thing with caching
+  evaluate(context: QueryContext, s: CSSComplexSelectorList): Element[] {
+    const result = this.query(context, s);
+    this._cache.clear();
+    return result;
+  }
+
+  private _cached<T>(main: any, rest: any[], cb: () => T): T {
+    if (!this._cache.has(main))
+      this._cache.set(main, []);
+    const entries = this._cache.get(main)!;
+    const entry = entries.find(e => {
+      return e.rest.length === rest.length &&
+          rest.findIndex((value, index) => e.rest[index] !== value) === -1;
+    });
+    if (entry)
+      return entry.result as T;
+    const result = cb();
+    entries.push({ rest, result });
+    return result;
+  }
+
+  private _checkSelector(s: Selector): CSSComplexSelector | CSSComplexSelectorList {
+    const wellFormed = typeof s === 'object' && s &&
+      (Array.isArray(s) || ('simples' in s) && (s.simples.length));
+    if (!wellFormed)
+      throw new Error(`Malformed selector "${s}"`);
+    return s as CSSComplexSelector | CSSComplexSelectorList;
+  }
+
+  matches(element: Element, s: Selector, context: QueryContext): boolean {
+    const selector = this._checkSelector(s);
+    return this._cached<boolean>(element, ['matches', selector, context], () => {
+      if (Array.isArray(selector))
+        return this._matchesEngine(isEngine, element, selector, context);
+      if (!this._matchesSimple(element, selector.simples[selector.simples.length - 1].selector, context))
+        return false;
+      return this._matchesParents(element, selector, selector.simples.length - 2, context);
+    });
+  }
+
+  query(context: QueryContext, s: any): Element[] {
+    const selector = this._checkSelector(s);
+    return this._cached<Element[]>(selector, ['query', context], () => {
+      if (Array.isArray(selector))
+        return this._queryEngine(isEngine, context, selector);
+      const elements = this._querySimple(context, selector.simples[selector.simples.length - 1].selector);
+      return elements.filter(element => this._matchesParents(element, selector, selector.simples.length - 2, context));
+    });
+  }
+
+  private _matchesSimple(element: Element, simple: CSSSimpleSelector, context: QueryContext): boolean {
+    return this._cached<boolean>(element, ['_matchesSimple', simple, context], () => {
+      const isScopeClause = simple.functions.some(f => f.name === 'scope');
+      if (!isScopeClause && element === context.scope)
+        return false;
+      if (simple.css && !this._matchesCSS(element, simple.css))
+        return false;
+      for (const func of simple.functions) {
+        if (!this._matchesEngine(this._getEngine(func.name), element, func.args, context))
+          return false;
+      }
+      return true;
+    });
+  }
+
+  private _querySimple(context: QueryContext, simple: CSSSimpleSelector): Element[] {
+    return this._cached<Element[]>(simple, ['_querySimple', context], () => {
+      let css = simple.css;
+      const funcs = simple.functions;
+      if (css === '*' && funcs.length)
+        css = undefined;
+
+      let elements: Element[];
+      let firstIndex = -1;
+      if (css !== undefined) {
+        elements = this._queryCSS(context, css);
+      } else {
+        firstIndex = funcs.findIndex(func => this._getEngine(func.name).query !== undefined);
+        if (firstIndex === -1)
+          firstIndex = 0;
+        elements = this._queryEngine(this._getEngine(funcs[firstIndex].name), context, funcs[firstIndex].args);
+      }
+      for (let i = 0; i < funcs.length; i++) {
+        if (i === firstIndex)
+          continue;
+        const engine = this._getEngine(funcs[i].name);
+        if (engine.matches !== undefined)
+          elements = elements.filter(e => this._matchesEngine(engine, e, funcs[i].args, context));
+      }
+      for (let i = 0; i < funcs.length; i++) {
+        if (i === firstIndex)
+          continue;
+        const engine = this._getEngine(funcs[i].name);
+        if (engine.matches === undefined)
+          elements = elements.filter(e => this._matchesEngine(engine, e, funcs[i].args, context));
+      }
+      return elements;
+    });
+  }
+
+  private _matchesParents(element: Element, complex: CSSComplexSelector, index: number, context: QueryContext): boolean {
+    return this._cached<boolean>(element, ['_matchesParents', complex, index, context], () => {
+      if (index < 0)
+        return true;
+      const { selector: simple, combinator } = complex.simples[index];
+      if (combinator === '>') {
+        const parent = parentElementOrShadowHostInScope(element, context.scope);
+        if (!parent || !this._matchesSimple(parent, simple, context))
+          return false;
+        return this._matchesParents(parent, complex, index - 1, context);
+      }
+      if (combinator === '+') {
+        const previousSibling = element === context.scope ? null : element.previousElementSibling;
+        if (!previousSibling || !this._matchesSimple(previousSibling, simple, context))
+          return false;
+        return this._matchesParents(previousSibling, complex, index - 1, context);
+      }
+      if (combinator === '') {
+        let parent = parentElementOrShadowHostInScope(element, context.scope);
+        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 = parentElementOrShadowHostInScope(parent, context.scope);
+        }
+        return false;
+      }
+      if (combinator === '~') {
+        let previousSibling = element === context.scope ? null : element.previousElementSibling;
+        while (previousSibling) {
+          if (this._matchesSimple(previousSibling, simple, context)) {
+            if (this._matchesParents(previousSibling, complex, index - 1, context))
+              return true;
+            if (complex.simples[index - 1].combinator === '~')
+              break;
+          }
+          previousSibling = previousSibling === context.scope ? null : previousSibling.previousElementSibling;
+        }
+        return false;
+      }
+      throw new Error(`Unsupported combinator "${combinator}"`);
+    });
+  }
+
+  private _matchesEngine(engine: SelectorEngine, element: Element, args: CSSFunctionArgument[], context: QueryContext): boolean {
+    if (engine.matches)
+      return this._callMatches(engine, element, args, context);
+    if (engine.query)
+      return this._callQuery(engine, args, context).includes(element);
+    throw new Error(`Selector engine should implement "matches" or "query"`);
+  }
+
+  private _queryEngine(engine: SelectorEngine, context: QueryContext, args: CSSFunctionArgument[]): Element[] {
+    if (engine.query)
+      return this._callQuery(engine, args, context);
+    if (engine.matches)
+      return this._queryCSS(context, '*').filter(element => this._callMatches(engine, element, args, context));
+    throw new Error(`Selector engine should implement "matches" or "query"`);
+  }
+
+  private _callMatches(engine: SelectorEngine, element: Element, args: CSSFunctionArgument[], context: QueryContext): boolean {
+    return this._cached<boolean>(element, ['_callMatches', engine, args, context.scope], () => {
+      return engine.matches!(element, args, context, this);
+    });
+  }
+
+  private _callQuery(engine: SelectorEngine, args: CSSFunctionArgument[], context: QueryContext): Element[] {
+    return this._cached<Element[]>(args, ['_callQuery', engine, context.scope], () => {
+      return engine.query!(context, args, this);
+    });
+  }
+
+  private _matchesCSS(element: Element, css: string): boolean {
+    return this._cached<boolean>(element, ['_matchesCSS', css], () => {
+      return element.matches(css);
+    });
+  }
+
+  private _queryCSS(context: QueryContext, css: string): Element[] {
+    return this._cached<Element[]>(css, ['_queryCSS', context], () => {
+      const result: Element[] = [];
+      function query(root: Element | ShadowRoot | Document) {
+        result.push(...root.querySelectorAll(css));
+        if ((root as Element).shadowRoot)
+          query((root as Element).shadowRoot!);
+        for (const element of root.querySelectorAll('*')) {
+          if (element.shadowRoot)
+            query(element.shadowRoot);
+        }
+      }
+      query(context.scope);
+      return result;
+    });
+  }
+
+  private _getEngine(name: string): SelectorEngine {
+    const engine = this._engines.get(name);
+    if (!engine)
+      throw new Error(`Unknown selector engine "${name}"`);
+    return engine;
+  }
+}
+
+const isEngine: SelectorEngine = {
+  matches(element: Element, args: any[], context: QueryContext, evaluator: SelectorEvaluator): boolean {
+    if (args.length === 0)
+      throw new Error(`"is" engine expects non-empty selector list`);
+    return args.some(selector => evaluator.matches(element, selector, context));
+  },
+
+  query(context: QueryContext, args: any[], evaluator: SelectorEvaluator): Element[] {
+    if (args.length === 0)
+      throw new Error(`"is" engine expects non-empty selector list`);
+    const elements: Element[] = [];
+    for (const arg of args)
+      elements.push(...evaluator.query(context, arg));
+    const result = Array.from(new Set(elements));
+    return args.length > 1 ? sortInDOMOrder(result) : result;
+  },
+};
+
+const hasEngine: SelectorEngine = {
+  matches(element: Element, args: any[], context: QueryContext, evaluator: SelectorEvaluator): boolean {
+    if (args.length === 0)
+      throw new Error(`"has" engine expects non-empty selector list`);
+    return evaluator.query({ ...context, scope: element }, args).length > 0;
+  },
+
+  // TODO: we can implement efficient "query" by matching "args" and returning
+  // all parents/descendants, just have to be careful with the ":scope" matching.
+};
+
+const scopeEngine: SelectorEngine = {
+  matches(element: Element, args: any[], context: QueryContext, evaluator: SelectorEvaluator): boolean {
+    if (args.length !== 0)
+      throw new Error(`"scope" engine expects no arguments`);
+    if (context.scope.nodeType === 9 /* Node.DOCUMENT_NODE */)
+      return element === (context.scope as Document).documentElement;
+    return element === context.scope;
+  },
+
+  query(context: QueryContext, args: any[], evaluator: SelectorEvaluator): Element[] {
+    if (args.length !== 0)
+      throw new Error(`"scope" engine expects no arguments`);
+    if (context.scope.nodeType === 9 /* Node.DOCUMENT_NODE */) {
+      const root = (context.scope as Document).documentElement;
+      return root ? [root] : [];
+    }
+    if (context.scope.nodeType === 1 /* Node.ELEMENT_NODE */)
+      return [context.scope as Element];
+    return [];
+  },
+};
+
+const notEngine: SelectorEngine = {
+  matches(element: Element, args: any[], context: QueryContext, evaluator: SelectorEvaluator): boolean {
+    if (args.length === 0)
+      throw new Error(`"not" engine expects non-empty selector list`);
+    return !evaluator.matches(element, args, context);
+  },
+};
+
+function parentElementOrShadowHost(element: Element): Element | undefined {
+  if (element.parentElement)
+    return element.parentElement;
+  if (!element.parentNode)
+    return;
+  if (element.parentNode.nodeType === Node.DOCUMENT_FRAGMENT_NODE && (element.parentNode as ShadowRoot).host)
+    return (element.parentNode as ShadowRoot).host;
+}
+
+function parentElementOrShadowHostInScope(element: Element, scope: Element | ShadowRoot | Document): Element | undefined {
+  return element === scope ? undefined : parentElementOrShadowHost(element);
+}
+
+function sortInDOMOrder(elements: Element[]): Element[] {
+  type SortEntry = { children: Element[], taken: boolean };
+
+  const elementToEntry = new Map<Element, SortEntry>();
+  const roots: Element[] = [];
+  const result: Element[] = [];
+
+  function append(element: Element): SortEntry {
+    let entry = elementToEntry.get(element);
+    if (entry)
+      return entry;
+    const parent = parentElementOrShadowHost(element);
+    if (parent) {
+      const parentEntry = append(parent);
+      parentEntry.children.push(element);
+    } else {
+      roots.push(element);
+    }
+    entry = { children: [], taken: false };
+    elementToEntry.set(element, entry);
+    return entry;
+  }
+  elements.forEach(e => append(e).taken = true);
+
+  function visit(element: Element) {
+    const entry = elementToEntry.get(element)!;
+    if (entry.taken)
+      result.push(element);
+    if (entry.children.length > 1) {
+      const set = new Set(entry.children);
+      entry.children = [];
+      let child = element.firstElementChild;
+      while (child && entry.children.length < set.size) {
+        if (set.has(child))
+          entry.children.push(child);
+        child = child.nextElementSibling;
+      }
+      child = element.shadowRoot ? element.shadowRoot.firstElementChild : null;
+      while (child && entry.children.length < set.size) {
+        if (set.has(child))
+          entry.children.push(child);
+        child = child.nextElementSibling;
+      }
+    }
+    entry.children.forEach(visit);
+  }
+  roots.forEach(visit);
+
+  return result;
+}

src/server/injected/utilityScript.webpack.config.js

@@ -23,7 +23,7 @@ module.exports = {
   module: {
     rules: [
       {
-        test: /\.tsx?$/,
+        test: /\.(j|t)sx?$/,
         loader: 'ts-loader',
         options: {
           transpileOnly: true

test/css-parser.spec.ts

@@ -56,6 +56,8 @@ it('should parse css', async () => {
   expect(serialize(parseCSS(':right-of(span):react(foobar)'))).toBe(':right-of(span):react(foobar)');
   expect(serialize(parseCSS('div:is(span):hover'))).toBe('div:hover:is(span)');
   expect(serialize(parseCSS('div:scope:hover'))).toBe('div:hover:scope()');
+  expect(serialize(parseCSS('div:sCOpe:HOVER'))).toBe('div:HOVER:scope()');
+  expect(serialize(parseCSS('div:NOT(span):hoVER'))).toBe('div:hoVER:not(span)');
 
   expect(serialize(parseCSS(':text("foo")'))).toBe(':text("foo")');
   expect(serialize(parseCSS(':text("*")'))).toBe(':text("*")');

test/selectors-css.spec.ts

@@ -153,6 +153,42 @@ it('should work with :not', async ({page, server}) => {
   expect(await page.$$eval(`css=div > :not(span):not(div)`, els => els.length)).toBe(0);
 });
 
+it('should work with ~', async ({page}) => {
+  await page.setContent(`
+    <div id=div1></div>
+    <div id=div2></div>
+    <div id=div3></div>
+    <div id=div4></div>
+    <div id=div5></div>
+    <div id=div6></div>
+  `);
+  expect(await page.$$eval(`css=#div1 ~ div ~ #div6`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=#div1 ~ div ~ div`, els => els.length)).toBe(4);
+  expect(await page.$$eval(`css=#div3 ~ div ~ div`, els => els.length)).toBe(2);
+  expect(await page.$$eval(`css=#div4 ~ div ~ div`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=#div5 ~ div ~ div`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=#div3 ~ #div2 ~ #div6`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=#div3 ~ #div4 ~ #div5`, els => els.length)).toBe(1);
+});
+
+it('should work with +', async ({page}) => {
+  await page.setContent(`
+    <div id=div1></div>
+    <div id=div2></div>
+    <div id=div3></div>
+    <div id=div4></div>
+    <div id=div5></div>
+    <div id=div6></div>
+  `);
+  expect(await page.$$eval(`css=#div1 ~ div + #div6`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=#div1 ~ div + div`, els => els.length)).toBe(4);
+  expect(await page.$$eval(`css=#div3 + div + div`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=#div4 ~ #div5 + div`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=#div5 + div + div`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=#div3 ~ #div2 + #div6`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=#div3 + #div4 + #div5`, els => els.length)).toBe(1);
+});
+
 it('should work with spaces in :nth-child and :not', test => {
   test.fixme('Our selector parser is broken');
 }, async ({page, server}) => {
@@ -167,3 +203,46 @@ it('should work with spaces in :nth-child and :not', test => {
   expect(await page.$$eval(`css=body :not(span, div)`, els => els.length)).toBe(1);
   expect(await page.$$eval(`css=span, section:not(span, div)`, els => els.length)).toBe(5);
 });
+
+it('should work with :is', test => {
+  test.skip('Needs a new selector evaluator');
+}, async ({page, server}) => {
+  await page.goto(server.PREFIX + '/deep-shadow.html');
+  expect(await page.$$eval(`css=div:is(#root1)`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=div:is(#root1, #target)`, els => els.length)).toBe(1);
+  expect(await page.$$eval(`css=div:is(span, #target)`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=div:is(span, #root1 > *)`, els => els.length)).toBe(2);
+  expect(await page.$$eval(`css=div:is(section div)`, els => els.length)).toBe(3);
+  expect(await page.$$eval(`css=:is(div, span)`, els => els.length)).toBe(7);
+  expect(await page.$$eval(`css=section:is(section) div:is(section div)`, els => els.length)).toBe(3);
+  expect(await page.$$eval(`css=:is(div, span) > *`, els => els.length)).toBe(6);
+});
+
+it('should work with :has', test => {
+  test.skip('Needs a new selector evaluator');
+}, async ({page, server}) => {
+  await page.goto(server.PREFIX + '/deep-shadow.html');
+  expect(await page.$$eval(`css=div:has(#target)`, els => els.length)).toBe(2);
+  expect(await page.$$eval(`css=div:has([data-testid=foo])`, els => els.length)).toBe(3);
+  expect(await page.$$eval(`css=div:has([attr*=value])`, els => els.length)).toBe(2);
+});
+
+it('should work with :scope', test => {
+  test.skip('Needs a new selector evaluator');
+}, async ({page, server}) => {
+  await page.goto(server.PREFIX + '/deep-shadow.html');
+  // 'is' does not change the scope, so it remains 'html'.
+  expect(await page.$$eval(`css=div:is(:scope#root1)`, els => els.length)).toBe(0);
+  expect(await page.$$eval(`css=div:is(:scope #root1)`, els => els.length)).toBe(1);
+  // 'has' does change the scope, so it becomes the 'div' we are querying.
+  expect(await page.$$eval(`css=div:has(:scope > #target)`, els => els.length)).toBe(1);
+
+  const handle = await page.$(`css=span`);
+  for (const scope of [page, handle]) {
+    expect(await scope.$$eval(`css=:scope`, els => els.length)).toBe(1);
+    expect(await scope.$$eval(`css=* :scope`, els => els.length)).toBe(0);
+    expect(await scope.$$eval(`css=* + :scope`, els => els.length)).toBe(0);
+    expect(await scope.$$eval(`css=* > :scope`, els => els.length)).toBe(0);
+    expect(await scope.$$eval(`css=* ~ :scope`, els => els.length)).toBe(0);
+  }
+});